📚 MBBS 1st Year Biochemistry

from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.units import cm, mm
from reportlab.pdfgen import canvas
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.platypus import Paragraph
from reportlab.lib.enums import TA_CENTER, TA_LEFT
import os

OUTPUT = "/home/daytona/workspace/lipid-pdf/Lipid_Quick_Reference.pdf"
W, H = A4   # 595.27 x 841.89 pts

# ── Colour palette ────────────────────────────────────────────
C_DARK_BLUE   = colors.HexColor("#1a3a5c")
C_BLUE        = colors.HexColor("#2563a8")
C_LIGHT_BLUE  = colors.HexColor("#dbeafe")
C_GREEN       = colors.HexColor("#16a34a")
C_LIGHT_GREEN = colors.HexColor("#dcfce7")
C_ORANGE      = colors.HexColor("#ea580c")
C_LIGHT_ORANGE= colors.HexColor("#ffedd5")
C_PURPLE      = colors.HexColor("#7c3aed")
C_LIGHT_PURPLE= colors.HexColor("#ede9fe")
C_RED         = colors.HexColor("#dc2626")
C_YELLOW      = colors.HexColor("#fef08a")
C_DARK        = colors.HexColor("#1e293b")
C_GRAY        = colors.HexColor("#64748b")
C_LIGHT_GRAY  = colors.HexColor("#f1f5f9")
C_WHITE       = colors.white
C_TEAL        = colors.HexColor("#0d9488")
C_LIGHT_TEAL  = colors.HexColor("#ccfbf1")

# ── Helpers ───────────────────────────────────────────────────
def draw_rounded_box(c, x, y, w, h, fill, stroke=None, radius=6):
    c.setFillColor(fill)
    if stroke:
        c.setStrokeColor(stroke)
        c.setLineWidth(1.2)
    else:
        c.setStrokeColor(fill)
        c.setLineWidth(0)
    c.roundRect(x, y, w, h, radius, fill=1, stroke=1 if stroke else 0)

def draw_text(c, text, x, y, size=9, color=C_DARK, bold=False, align="center", max_width=None):
    c.setFillColor(color)
    font = "Helvetica-Bold" if bold else "Helvetica"
    c.setFont(font, size)
    if align == "center":
        c.drawCentredString(x, y, text)
    elif align == "left":
        c.drawString(x, y, text)
    elif align == "right":
        c.drawRightString(x, y, text)

def draw_arrow_down(c, x, y, length=18, color=C_GRAY):
    c.setStrokeColor(color)
    c.setFillColor(color)
    c.setLineWidth(1.5)
    c.line(x, y, x, y - length + 6)
    # arrowhead
    p = c.beginPath()
    p.moveTo(x, y - length)
    p.lineTo(x - 5, y - length + 8)
    p.lineTo(x + 5, y - length + 8)
    p.close()
    c.drawPath(p, fill=1, stroke=0)

def draw_arrow_right(c, x, y, length=22, color=C_GRAY):
    c.setStrokeColor(color)
    c.setFillColor(color)
    c.setLineWidth(1.5)
    c.line(x, y, x + length - 6, y)
    p = c.beginPath()
    p.moveTo(x + length, y)
    p.lineTo(x + length - 8, y + 5)
    p.lineTo(x + length - 8, y - 5)
    p.close()
    c.drawPath(p, fill=1, stroke=0)

def step_box(c, cx, y, w, h, label, sublabel="", fill=C_LIGHT_BLUE, stroke=C_BLUE,
             label_color=C_DARK_BLUE, sub_color=C_GRAY, bold_label=True):
    x = cx - w/2
    draw_rounded_box(c, x, y - h, w, h, fill, stroke, radius=7)
    if sublabel:
        draw_text(c, label, cx, y - h*0.38, size=8.5, color=label_color, bold=bold_label)
        draw_text(c, sublabel, cx, y - h*0.72, size=7, color=sub_color)
    else:
        draw_text(c, label, cx, y - h*0.55, size=8.5, color=label_color, bold=bold_label)

def side_label(c, x, y, text, color=C_ORANGE, size=7):
    """Small italic enzyme label to the side of an arrow"""
    c.setFillColor(color)
    c.setFont("Helvetica-Oblique", size)
    c.drawString(x, y, text)

# ═══════════════════════════════════════════════════════════════
#  PAGE 1 — Cover
# ═══════════════════════════════════════════════════════════════
def draw_cover(c):
    # Background gradient-like effect
    c.setFillColor(C_DARK_BLUE)
    c.rect(0, 0, W, H, fill=1, stroke=0)

    # Top accent stripe
    c.setFillColor(C_BLUE)
    c.rect(0, H - 120, W, 120, fill=1, stroke=0)

    # Decorative circles
    for (cx2, cy2, r, alpha) in [(500, 750, 120, 0.08), (80, 200, 90, 0.06), (300, 400, 200, 0.04)]:
        c.setFillColor(colors.HexColor("#ffffff"))
        c.setFillAlpha(alpha)
        c.circle(cx2, cy2, r, fill=1, stroke=0)
    c.setFillAlpha(1)

    # Title block
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 32)
    c.drawCentredString(W/2, H - 200, "LIPID BIOCHEMISTRY")
    c.setFont("Helvetica-Bold", 22)
    c.setFillColor(colors.HexColor("#93c5fd"))
    c.drawCentredString(W/2, H - 235, "Quick Reference Guide")

    # Subtitle
    c.setFont("Helvetica", 13)
    c.setFillColor(colors.HexColor("#cbd5e1"))
    c.drawCentredString(W/2, H - 265, "MBBS 1st Year  ·  Biochemistry")

    # Divider line
    c.setStrokeColor(colors.HexColor("#3b82f6"))
    c.setLineWidth(2)
    c.line(80, H - 285, W - 80, H - 285)

    # Contents
    topics = [
        ("📋", "Beta-Oxidation of Palmitic Acid", "Step-by-step flowchart + ATP calculation"),
        ("🔬", "Cholesterol Synthesis", "HMG CoA → Cholesterol pathway + regulation"),
        ("⚡", "Key Enzymes & Regulation", "Rate-limiting steps, inhibitors, activators"),
        ("🧪", "ATP Yield Summary", "Complete energy accounting table"),
    ]
    y0 = H - 330
    for icon, title, desc in topics:
        draw_rounded_box(c, 70, y0 - 42, W - 140, 46, fill=colors.HexColor("#1e3a5f"), stroke=colors.HexColor("#3b82f6"), radius=8)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 11)
        c.drawString(90, y0 - 18, f"{icon}  {title}")
        c.setFillColor(colors.HexColor("#94a3b8"))
        c.setFont("Helvetica", 9)
        c.drawString(90, y0 - 33, desc)
        y0 -= 58

    # For exam badge
    draw_rounded_box(c, W/2 - 130, 80, 260, 50, fill=colors.HexColor("#854d0e"), stroke=colors.HexColor("#f59e0b"), radius=10)
    c.setFillColor(colors.HexColor("#fef08a"))
    c.setFont("Helvetica-Bold", 11)
    c.drawCentredString(W/2, 113, "⭐  HIGH YIELD FOR UNIVERSITY EXAMS")
    c.setFont("Helvetica", 8.5)
    c.setFillColor(colors.HexColor("#fde68a"))
    c.drawCentredString(W/2, 96, "Most repeated topics 2013–2023")

    # Page number placeholder
    c.setFillColor(colors.HexColor("#475569"))
    c.setFont("Helvetica", 8)
    c.drawCentredString(W/2, 40, "Page 1 of 4")

# ═══════════════════════════════════════════════════════════════
#  PAGE 2 — Beta-Oxidation Flowchart
# ═══════════════════════════════════════════════════════════════
def draw_beta_ox(c):
    # Header
    c.setFillColor(C_DARK_BLUE)
    c.rect(0, H - 55, W, 55, fill=1, stroke=0)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 17)
    c.drawCentredString(W/2, H - 22, "β-OXIDATION OF PALMITIC ACID (C16:0)")
    c.setFont("Helvetica", 9)
    c.setFillColor(colors.HexColor("#93c5fd"))
    c.drawCentredString(W/2, H - 40, "Mitochondrial Matrix  ·  7 cycles → 8 Acetyl CoA")

    # ── LEFT column: Pre-oxidation steps ──────────────────────
    col_l = W * 0.25
    col_r = W * 0.72
    BW = 155  # box width
    BH = 36   # box height

    # === ACTIVATION (cytoplasm) ===
    y = H - 80
    draw_rounded_box(c, 20, y - 22, W - 40, 22, fill=colors.HexColor("#fef9c3"), stroke=colors.HexColor("#ca8a04"), radius=4)
    c.setFillColor(colors.HexColor("#78350f"))
    c.setFont("Helvetica-Bold", 8.5)
    c.drawString(30, y - 16, "STEP 0  —  ACTIVATION  (Cytoplasm, Outer Mitochondrial Membrane)")

    y -= 35
    step_box(c, col_l, y, BW, BH, "Palmitic Acid (C16)",
             "Free fatty acid", fill=C_LIGHT_ORANGE, stroke=C_ORANGE, label_color=C_ORANGE)

    side_label(c, col_l + BW/2 + 5, y - BH - 5, "Acyl CoA Synthetase", color=C_ORANGE)
    side_label(c, col_l + BW/2 + 5, y - BH - 15, "ATP → AMP + PPi", color=C_GRAY)
    draw_arrow_down(c, col_l, y - BH - 2, 22)

    y -= BH + 28
    step_box(c, col_l, y, BW, BH, "Palmitoyl CoA",
             "Activated form (-2 ATP)", fill=C_LIGHT_ORANGE, stroke=C_ORANGE, label_color=C_ORANGE)

    # === CARNITINE SHUTTLE ===
    y -= BH + 10
    draw_rounded_box(c, 20, y - 22, W - 40, 22, fill=C_LIGHT_PURPLE, stroke=C_PURPLE, radius=4)
    c.setFillColor(C_PURPLE)
    c.setFont("Helvetica-Bold", 8.5)
    c.drawString(30, y - 16, "CARNITINE SHUTTLE  —  Transport across Inner Mitochondrial Membrane")

    shuttle_items = [
        ("Palmitoyl CoA", "Cytosol side"),
        ("Palmitoylcarnitine", "CPT-I converts (RATE-LIMITING)"),
        ("Palmitoyl CoA", "Matrix side (CPT-II regenerates)"),
    ]
    y -= 30
    sx = 55
    for i, (name, note) in enumerate(shuttle_items):
        draw_rounded_box(c, sx, y - BH, 140, BH, fill=C_LIGHT_PURPLE, stroke=C_PURPLE, radius=6)
        c.setFillColor(C_PURPLE)
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(sx + 70, y - BH*0.38, name)
        c.setFillColor(C_GRAY)
        c.setFont("Helvetica", 7)
        c.drawCentredString(sx + 70, y - BH*0.72, note)
        if i < 2:
            draw_arrow_right(c, sx + 140, y - BH/2, 22)
            sx += 162
    # CPT-I inhibited by malonyl CoA
    c.setFillColor(C_RED)
    c.setFont("Helvetica-Bold", 7.5)
    c.drawString(55 + 140 + 5, y - BH + 5, "⊗ Inhibited by Malonyl CoA (prevents futile cycle)")

    # === BETA-OXIDATION CYCLE ===
    y -= BH + 22
    draw_rounded_box(c, 20, y - 22, W - 40, 22, fill=C_LIGHT_GREEN, stroke=C_GREEN, radius=4)
    c.setFillColor(C_GREEN)
    c.setFont("Helvetica-Bold", 8.5)
    c.drawString(30, y - 16, "β-OXIDATION CYCLE  ×7  (4 reactions per cycle — inside Mitochondrial Matrix)")

    # Draw 4-step cycle in two rows
    cycle_steps = [
        ("① Dehydrogenation", "Acyl CoA Dehydrogenase\n(FAD → FADH₂)", C_LIGHT_BLUE, C_BLUE),
        ("② Hydration", "Enoyl CoA Hydratase\n(adds H₂O)", C_LIGHT_GREEN, C_GREEN),
        ("③ Dehydrogenation", "3-OH Acyl CoA Dehydrogenase\n(NAD⁺ → NADH)", C_LIGHT_ORANGE, C_ORANGE),
        ("④ Thiolysis", "Beta-Ketothiolase\n(+ CoA → Acetyl CoA)", C_LIGHT_PURPLE, C_PURPLE),
    ]
    y -= 30
    cx_start = 80
    dx = 118
    for i, (title, enzyme, fill, stroke) in enumerate(cycle_steps):
        bx = cx_start + i * dx
        draw_rounded_box(c, bx, y - 48, 108, 48, fill=fill, stroke=stroke, radius=7)
        c.setFillColor(stroke)
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(bx + 54, y - 16, title)
        lines = enzyme.split("\n")
        c.setFillColor(C_DARK)
        c.setFont("Helvetica", 7)
        c.drawCentredString(bx + 54, y - 29, lines[0])
        c.setFillColor(C_GRAY)
        c.drawCentredString(bx + 54, y - 40, lines[1])
        if i < 3:
            draw_arrow_right(c, bx + 108, y - 24, 10)

    # Curved "×7" arrow back
    y -= 48
    draw_rounded_box(c, W/2 - 90, y - 28, 180, 28, fill=colors.HexColor("#fef9c3"), stroke=colors.HexColor("#d97706"), radius=6)
    c.setFillColor(colors.HexColor("#92400e"))
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(W/2, y - 11, "🔁  Repeat ×7   →   7 FADH₂  +  7 NADH  +  8 Acetyl CoA")

    # Product boxes
    y -= 42
    draw_rounded_box(c, 20, y - 22, W - 40, 22, fill=C_LIGHT_GRAY, stroke=C_GRAY, radius=4)
    c.setFillColor(C_DARK)
    c.setFont("Helvetica-Bold", 8.5)
    c.drawString(30, y - 16, "PRODUCTS ENTER  ——  8 Acetyl CoA → TCA Cycle  ·  FADH₂ + NADH → ETC")

    # === ATP TABLE ===
    y -= 38
    draw_rounded_box(c, 20, y - 22, W - 40, 22, fill=C_DARK_BLUE, stroke=C_DARK_BLUE, radius=4)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(W/2, y - 15, "⚡  NET ATP YIELD FROM PALMITIC ACID (C16:0)")

    headers = ["Source", "Count", "ATP each", "Total ATP"]
    col_x = [30, 210, 310, 420]
    col_w = [180, 95, 95, 95]
    y -= 28

    # Table header
    for i, (hdr, cx2) in enumerate(zip(headers, col_x)):
        draw_rounded_box(c, cx2, y - 18, col_w[i] - 4, 18, fill=C_BLUE, stroke=C_BLUE, radius=3)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(cx2 + col_w[i]/2 - 2, y - 12, hdr)

    rows = [
        ("8 × Acetyl CoA  (via TCA cycle)", "8", "10", "80"),
        ("7 × NADH  (from β-oxidation)", "7", "2.5", "17.5"),
        ("7 × FADH₂  (from β-oxidation)", "7", "1.5", "10.5"),
        ("Activation cost (ATP → AMP)", "1", "-2", "-2"),
    ]
    fills = [C_LIGHT_GREEN, C_LIGHT_BLUE, C_LIGHT_ORANGE, colors.HexColor("#fee2e2")]

    y -= 22
    for j, (row, rf) in enumerate(zip(rows, fills)):
        for i, (val, cx2) in enumerate(zip(row, col_x)):
            draw_rounded_box(c, cx2, y - 16, col_w[i] - 4, 16, fill=rf, stroke=colors.HexColor("#e2e8f0"), radius=2)
            c.setFillColor(C_DARK)
            c.setFont("Helvetica-Bold" if i == 0 else "Helvetica", 8)
            c.drawCentredString(cx2 + col_w[i]/2 - 2, y - 11, val)
        y -= 18

    # Total row
    draw_rounded_box(c, 30, y - 20, W - 70, 20, fill=C_DARK_BLUE, stroke=C_DARK_BLUE, radius=4)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 10)
    c.drawString(40, y - 14, "NET ATP  =  80 + 17.5 + 10.5 - 2  =")
    c.setFillColor(C_YELLOW)
    c.setFont("Helvetica-Bold", 12)
    c.drawString(310, y - 14, "106 ATP")

    # Footer
    c.setFillColor(C_GRAY)
    c.setFont("Helvetica", 7.5)
    c.drawString(30, 22, "* Using modern P/O ratios: NADH = 2.5 ATP, FADH₂ = 1.5 ATP  |  Oleic acid (C18:1) yields ~2 ATP less (one FADH₂ saved by isomerase step)")
    c.setFont("Helvetica", 8)
    c.drawCentredString(W/2, 10, "Page 2 of 4")

# ═══════════════════════════════════════════════════════════════
#  PAGE 3 — Cholesterol Synthesis Flowchart
# ═══════════════════════════════════════════════════════════════
def draw_cholesterol(c):
    # Header
    c.setFillColor(C_GREEN)
    c.rect(0, H - 55, W, 55, fill=1, stroke=0)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 17)
    c.drawCentredString(W/2, H - 22, "CHOLESTEROL SYNTHESIS  (de novo)")
    c.setFont("Helvetica", 9)
    c.setFillColor(C_LIGHT_GREEN)
    c.drawCentredString(W/2, H - 40, "Cytosol & SER  ·  All 27 carbons from Acetyl CoA  ·  Site: Liver (mainly)")

    CX = W / 2   # centre column
    BW2 = 230
    BH2 = 34
    y = H - 75

    stages = [
        # (label, sublabel, fill, stroke, enzyme_label, cosubstrate, stage_header)
        ("Acetyl CoA  (2C)", "Starting material — from pyruvate/FA oxidation",
         C_LIGHT_ORANGE, C_ORANGE, None, None,
         "STAGE 1  —  Formation of HMG CoA  (Mitochondria & Cytosol)"),

        ("Acetoacetyl CoA  (4C)", "Thiolase reaction",
         C_LIGHT_ORANGE, C_ORANGE, "Thiolase (2 Acetyl CoA → 1 Acetoacetyl CoA)", None, None),

        ("HMG CoA  (6C)", "3-Hydroxy-3-Methylglutaryl CoA",
         C_LIGHT_ORANGE, C_ORANGE, "HMG CoA Synthase", None, None),

        ("Mevalonate  (6C)", "★ RATE-LIMITING STEP",
         C_LIGHT_GREEN, C_GREEN, "★ HMG CoA Reductase  (2 NADPH used)",
         "← Target of STATINS", "STAGE 2  —  Mevalonate Synthesis  (RATE-LIMITING)"),

        ("Mevalonate-5-Phosphate", "Phosphorylation step",
         C_LIGHT_BLUE, C_BLUE, "Mevalonate Kinase (ATP)", None,
         "STAGE 3  —  Activation & Decarboxylation"),

        ("Mevalonate-5-Pyrophosphate", "Second phosphorylation",
         C_LIGHT_BLUE, C_BLUE, "Phosphomevalonate Kinase (ATP)", None, None),

        ("Isopentenyl Pyrophosphate (IPP, 5C)", "Active isoprene unit",
         C_LIGHT_BLUE, C_BLUE, "Mevalonate-PP Decarboxylase (CO₂ released, ATP)", None, None),

        ("Geranyl-PP (10C)  →  Farnesyl-PP (15C)", "2 IPP units → GPP → 3 IPP → FPP",
         C_LIGHT_PURPLE, C_PURPLE, "Geranyl / Farnesyl Transferases", None,
         "STAGE 4  —  Squalene Synthesis"),

        ("Squalene  (30C)", "2 × Farnesyl-PP → Squalene",
         C_LIGHT_PURPLE, C_PURPLE, "Squalene Synthase  (2 NADPH)", None, None),

        ("Lanosterol  (30C)", "First sterol intermediate — ring formation",
         colors.HexColor("#fce7f3"), colors.HexColor("#db2777"),
         "Squalene Monooxygenase + Cyclase (O₂, NADPH)", None,
         "STAGE 5  —  Cyclization & Side-chain Modifications  (SER)"),

        ("Cholesterol  (27C)", "Final product — 3 carbons lost",
         C_LIGHT_GREEN, C_GREEN, "~19 enzyme steps (demethylation, reduction, desaturation)", None, None),
    ]

    y -= 5
    prev_had_header = True
    for i, item in enumerate(stages):
        label, sublabel, fill, stroke, enzyme, cosub, stage_hdr = item

        if stage_hdr:
            if not prev_had_header:
                y -= 6
            draw_rounded_box(c, 20, y - 18, W - 40, 18, fill=C_DARK_BLUE, stroke=C_DARK_BLUE, radius=3)
            c.setFillColor(C_WHITE)
            c.setFont("Helvetica-Bold", 7.5)
            c.drawString(28, y - 13, stage_hdr)
            y -= 22
            prev_had_header = True
        else:
            prev_had_header = False

        # Enzyme label above arrow
        if enzyme and i > 0:
            enz_lines = enzyme.split(" (")
            c.setFillColor(C_ORANGE)
            c.setFont("Helvetica-Oblique", 7)
            c.drawCentredString(CX + BW2/2 + 45, y - 6, enz_lines[0])
            if len(enz_lines) > 1:
                c.setFillColor(C_GRAY)
                c.drawCentredString(CX + BW2/2 + 45, y - 14, "(" + enz_lines[1])
            if cosub:
                c.setFillColor(C_RED)
                c.setFont("Helvetica-Bold", 7)
                c.drawCentredString(CX + BW2/2 + 45, y - 22, cosub)
            draw_arrow_down(c, CX, y - 2, 18, color=C_GREEN if stroke == C_GREEN else C_GRAY)
            y -= 22

        step_box(c, CX, y, BW2, BH2, label, sublabel, fill=fill, stroke=stroke,
                 label_color=stroke, sub_color=C_GRAY)
        y -= BH2 + 2

    # Regulation box on right side
    reg_x = W - 165
    reg_y = H - 280
    draw_rounded_box(c, reg_x, reg_y - 220, 150, 220, fill=colors.HexColor("#fff7ed"), stroke=colors.HexColor("#d97706"), radius=8)
    c.setFillColor(colors.HexColor("#92400e"))
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(reg_x + 75, reg_y - 14, "⚙  REGULATION")
    c.drawCentredString(reg_x + 75, reg_y - 26, "HMG CoA Reductase")

    reg_items = [
        ("✅ ACTIVATORS:", C_GREEN, True),
        ("Insulin", C_DARK, False),
        ("Thyroid hormone (T3)", C_DARK, False),
        ("", C_DARK, False),
        ("⊗ INHIBITORS:", C_RED, True),
        ("Cholesterol (SREBP↓)", C_DARK, False),
        ("Glucagon", C_DARK, False),
        ("Glucocorticoids", C_DARK, False),
        ("Statins (drugs)", C_DARK, False),
        ("", C_DARK, False),
        ("💊 STATINS:", colors.HexColor("#7c3aed"), True),
        ("Competitive inhibitors", C_DARK, False),
        ("↓ LDL cholesterol", C_DARK, False),
        ("e.g. Atorvastatin,", C_DARK, False),
        ("Rosuvastatin", C_DARK, False),
    ]
    ry = reg_y - 44
    for text, color, bold in reg_items:
        if text:
            c.setFillColor(color)
            c.setFont("Helvetica-Bold" if bold else "Helvetica", 7.5)
            c.drawString(reg_x + 8, ry, text)
        ry -= 12

    # Footnote
    c.setFillColor(C_GRAY)
    c.setFont("Helvetica", 7.5)
    c.drawString(20, 25, "Downstream products of Mevalonate pathway: Cholesterol, Dolichol, Ubiquinone, Isoprenoids, Farnesyl groups (protein prenylation)")
    c.setFont("Helvetica", 8)
    c.drawCentredString(W/2, 10, "Page 3 of 4")

# ═══════════════════════════════════════════════════════════════
#  PAGE 4 — Key Enzymes, Regulation & Exam Tips
# ═══════════════════════════════════════════════════════════════
def draw_summary(c):
    # Header
    c.setFillColor(C_PURPLE)
    c.rect(0, H - 55, W, 55, fill=1, stroke=0)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 17)
    c.drawCentredString(W/2, H - 22, "KEY ENZYMES, REGULATION & EXAM TIPS")
    c.setFont("Helvetica", 9)
    c.setFillColor(C_LIGHT_PURPLE)
    c.drawCentredString(W/2, H - 40, "High-Yield Summary for University Exams  ·  Lipid Biochemistry")

    y = H - 75

    # ── Comparison table: Beta-ox vs FA Synthesis ─────────────
    draw_rounded_box(c, 15, y - 18, W - 30, 18, fill=C_DARK_BLUE, stroke=C_DARK_BLUE, radius=4)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(W/2, y - 13, "BETA-OXIDATION  vs  FATTY ACID SYNTHESIS  —  Key Differences")
    y -= 24

    comp_headers = ["Feature", "β-Oxidation", "FA Synthesis"]
    comp_rows = [
        ("Location",          "Mitochondrial matrix",      "Cytosol"),
        ("Carrier",           "CoA",                        "ACP (Acyl Carrier Protein)"),
        ("Coenzyme",          "FAD, NAD⁺ (oxidation)",     "NADPH (reduction)"),
        ("CO₂ / HCO₃⁻",     "Not used",                   "HCO₃⁻ required (malonyl CoA)"),
        ("Rate-limiting enz.","Carnitine Palmitoyltransfer-I","Acetyl CoA Carboxylase (ACC)"),
        ("Regulation",        "Inhibited by malonyl CoA",  "Inhibited by palmitoyl CoA"),
        ("Main product",      "Acetyl CoA + FADH₂ + NADH", "Palmitate (C16:0)"),
        ("Activated by",      "Glucagon, epinephrine",     "Insulin, citrate"),
    ]
    col_x2 = [15, 160, 375]
    col_w2 = [145, 210, 205]
    hdr_fills = [C_BLUE, C_BLUE, C_GREEN]
    for i, (hdr, cx2, cw) in enumerate(zip(comp_headers, col_x2, col_w2)):
        draw_rounded_box(c, cx2, y - 16, cw - 3, 16, fill=hdr_fills[i], stroke=hdr_fills[i], radius=2)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(cx2 + cw/2 - 1.5, y - 11, hdr)
    y -= 18

    for j, row in enumerate(comp_rows):
        rf = C_LIGHT_GRAY if j % 2 == 0 else C_WHITE
        for i, (val, cx2, cw) in enumerate(zip(row, col_x2, col_w2)):
            cell_fill = rf if i > 0 else colors.HexColor("#e0f2fe")
            draw_rounded_box(c, cx2, y - 15, cw - 3, 15, fill=cell_fill, stroke=colors.HexColor("#cbd5e1"), radius=2)
            c.setFillColor(C_DARK)
            c.setFont("Helvetica-Bold" if i == 0 else "Helvetica", 7.5)
            c.drawCentredString(cx2 + cw/2 - 1.5, y - 10, val)
        y -= 16

    y -= 10

    # ── Two column section ─────────────────────────────────────
    # Left: Disorders | Right: Exam tips
    col1_x = 15
    col2_x = W/2 + 5
    col_width = W/2 - 25

    # Disorders box
    draw_rounded_box(c, col1_x, y - 18, col_width, 18, fill=C_RED, stroke=C_RED, radius=4)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(col1_x + col_width/2, y - 13, "⚠  CLINICAL DISORDERS")
    y -= 22

    disorders = [
        ("MCAD Deficiency",    "Medium-chain acyl CoA dehydrogenase def.\nHypoglycemia on fasting, no ketones"),
        ("Refsum Disease",     "Phytanoyl CoA α-hydroxylase def.\nPhytanic acid accumulation, neuropathy"),
        ("Zellweger Syndrome", "Peroxisome biogenesis disorder\nVLCFA accumulation, neurological defects"),
        ("X-ALD",              "VLCFA transport across peroxisomal membrane\nAdrenal + CNS demyelination"),
        ("Familial Hyper-     \ncholesterolemia",
                               "LDL receptor defect\nElevated LDL, xanthomas, early MI"),
    ]
    dy = y
    for dis, desc in disorders:
        draw_rounded_box(c, col1_x, dy - 34, col_width, 34, fill=colors.HexColor("#fff1f2"), stroke=colors.HexColor("#fca5a5"), radius=5)
        c.setFillColor(C_RED)
        c.setFont("Helvetica-Bold", 8)
        c.drawString(col1_x + 6, dy - 12, dis)
        lines = desc.split("\n")
        c.setFillColor(C_DARK)
        c.setFont("Helvetica", 7)
        c.drawString(col1_x + 6, dy - 22, lines[0])
        if len(lines) > 1:
            c.drawString(col1_x + 6, dy - 31, lines[1])
        dy -= 38

    # Exam tips box
    draw_rounded_box(c, col2_x, y - 18, col_width, 18, fill=colors.HexColor("#d97706"), stroke=colors.HexColor("#d97706"), radius=4)
    c.setFillColor(C_WHITE)
    c.setFont("Helvetica-Bold", 9)
    c.drawCentredString(col2_x + col_width/2, y - 13, "⭐  EXAM HIGH-YIELD POINTS")

    tips = [
        "ATP from palmitic acid = 106 (learn calculation steps)",
        "Oleic acid: 1 isomerase needed → ~2 ATP less than palmitate",
        "Beta-oxidation INHIBITED by malonyl CoA (CPT-I block)",
        "Acetyl CoA Carboxylase: rate-limiting in FA synthesis",
        "HMG CoA Reductase: rate-limiting in cholesterol synthesis",
        "Statins = competitive inhibitors of HMG CoA Reductase",
        "Carnitine needed only for LONG chain FA (>12C)",
        "Liver CANNOT use ketone bodies (lacks thiophorase)",
        "HDL = reverse cholesterol transport = 'good cholesterol'",
        "ApoC-II activates LPL; ApoB-100 = LDL receptor ligand",
        "Choline = most important lipotropic factor",
        "Linoleic acid (18:2, ω-6) = precursor of arachidonic acid",
        "LCAT esterifies cholesterol in HDL (needed for RCT)",
        "SREBP pathway: cholesterol ↑ → SREBP ↓ → HMG CoA red ↓",
    ]
    ty = y - 22
    for i, tip in enumerate(tips):
        bg = C_LIGHT_GREEN if i % 2 == 0 else C_YELLOW
        draw_rounded_box(c, col2_x, ty - 14, col_width, 14, fill=bg, stroke=colors.HexColor("#d1d5db"), radius=2)
        c.setFillColor(C_DARK)
        c.setFont("Helvetica", 7.5)
        c.drawString(col2_x + 6, ty - 10, f"✓  {tip}")
        ty -= 15

    # Footer
    c.setFillColor(C_GRAY)
    c.setFont("Helvetica", 7.5)
    c.drawCentredString(W/2, 25, "Sources: Lippincott's Illustrated Reviews Biochemistry 8e · Harper's Illustrated Biochemistry · WBUHS PYQ Bank 2010–2023")
    c.setFont("Helvetica-Bold", 8)
    c.setFillColor(C_DARK_BLUE)
    c.drawCentredString(W/2, 13, "Page 4 of 4  ·  Lipid Biochemistry Quick Reference — MBBS 1st Year")

# ═══════════════════════════════════════════════════════════════
#  MAIN
# ═══════════════════════════════════════════════════════════════
c = canvas.Canvas(OUTPUT, pagesize=A4)
c.setTitle("Lipid Biochemistry Quick Reference")
c.setAuthor("Orris Medical")
c.setSubject("MBBS 1st Year Biochemistry — Lipid Chemistry & Metabolism")

draw_cover(c);    c.showPage()
draw_beta_ox(c);  c.showPage()
draw_cholesterol(c); c.showPage()
draw_summary(c);  c.showPage()

c.save()
print(f"PDF saved: {OUTPUT}")

"""
MBBS 1st Year Biochemistry — Lipid Chemistry & Metabolism
Complete PYQ + Answers + Flowcharts PDF
"""
from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.lib.units import cm, mm
from reportlab.pdfgen import canvas as rl_canvas
from reportlab.platypus import (
    SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle,
    PageBreak, HRFlowable, KeepTogether
)
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_CENTER, TA_LEFT, TA_JUSTIFY
from reportlab.platypus.flowables import Flowable
import io

OUTPUT = "/home/daytona/workspace/lipid-pdf/Lipid_Complete_PYQ_Guide.pdf"
W, H = A4

# ── Colours ──────────────────────────────────────────────────
C_DARK_BLUE   = colors.HexColor("#1a3a5c")
C_BLUE        = colors.HexColor("#2563a8")
C_LIGHT_BLUE  = colors.HexColor("#dbeafe")
C_GREEN       = colors.HexColor("#16a34a")
C_LIGHT_GREEN = colors.HexColor("#dcfce7")
C_ORANGE      = colors.HexColor("#ea580c")
C_LIGHT_ORANGE= colors.HexColor("#ffedd5")
C_PURPLE      = colors.HexColor("#7c3aed")
C_LIGHT_PURPLE= colors.HexColor("#ede9fe")
C_RED         = colors.HexColor("#dc2626")
C_LIGHT_RED   = colors.HexColor("#fee2e2")
C_YELLOW      = colors.HexColor("#fef08a")
C_TEAL        = colors.HexColor("#0d9488")
C_LIGHT_TEAL  = colors.HexColor("#ccfbf1")
C_DARK        = colors.HexColor("#1e293b")
C_GRAY        = colors.HexColor("#64748b")
C_LIGHT_GRAY  = colors.HexColor("#f1f5f9")
C_WHITE       = colors.white
C_AMBER       = colors.HexColor("#d97706")
C_LIGHT_AMBER = colors.HexColor("#fef3c7")

# ════════════════════════════════════════════════════════════════
#  CUSTOM FLOWABLES
# ════════════════════════════════════════════════════════════════

class ColorBox(Flowable):
    """A colored rounded rectangle with title + body text."""
    def __init__(self, title, body_lines, fill, stroke, title_color=None,
                 width=None, padding=8, title_size=10, body_size=8.5):
        Flowable.__init__(self)
        self.title = title
        self.body_lines = body_lines  # list of (text, bold, color, indent)
        self.fill = fill
        self.stroke = stroke
        self.title_color = title_color or stroke
        self.width = width or (W - 80)
        self.padding = padding
        self.title_size = title_size
        self.body_size = body_size
        # Estimate height
        self.height = 20 + len(body_lines) * (body_size + 3) + padding * 2

    def draw(self):
        c = self.canv
        w, h = self.width, self.height
        # Background
        c.setFillColor(self.fill)
        c.setStrokeColor(self.stroke)
        c.setLineWidth(1.2)
        c.roundRect(0, 0, w, h, 7, fill=1, stroke=1)
        # Title bar
        c.setFillColor(self.stroke)
        c.roundRect(0, h - 22, w, 22, 7, fill=1, stroke=0)
        c.rect(0, h - 22, w, 11, fill=1, stroke=0)  # flatten bottom corners
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", self.title_size)
        c.drawString(self.padding, h - 15, self.title)
        # Body
        y = h - 28
        for (text, bold, col, indent) in self.body_lines:
            c.setFillColor(col or C_DARK)
            c.setFont("Helvetica-Bold" if bold else "Helvetica", self.body_size)
            c.drawString(self.padding + indent, y, text)
            y -= self.body_size + 3


class QuestionBox(Flowable):
    """Styled question header box."""
    def __init__(self, qnum, qtext, marks="", year="", width=None):
        Flowable.__init__(self)
        self.qnum = qnum
        self.qtext = qtext
        self.marks = marks
        self.year = year
        self.width = width or (W - 80)
        self.height = 36

    def draw(self):
        c = self.canv
        w, h = self.width, self.height
        c.setFillColor(C_DARK_BLUE)
        c.roundRect(0, 0, w, h, 6, fill=1, stroke=0)
        # Q number badge
        c.setFillColor(C_YELLOW)
        c.roundRect(6, 8, 28, 20, 4, fill=1, stroke=0)
        c.setFillColor(C_DARK)
        c.setFont("Helvetica-Bold", 9)
        c.drawCentredString(20, 15, self.qnum)
        # Question text
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 9)
        c.drawString(42, 22, self.qtext[:85])
        if len(self.qtext) > 85:
            c.drawString(42, 10, self.qtext[85:165])
        # Marks / year badge
        if self.marks or self.year:
            badge = []
            if self.marks: badge.append(self.marks)
            if self.year:  badge.append(self.year)
            badge_text = "  |  ".join(badge)
            c.setFillColor(C_ORANGE)
            c.roundRect(w - 115, 10, 108, 16, 4, fill=1, stroke=0)
            c.setFillColor(C_WHITE)
            c.setFont("Helvetica-Bold", 7.5)
            c.drawCentredString(w - 61, 15, badge_text)


class AnswerSection(Flowable):
    """Thin green answer label."""
    def __init__(self, width=None):
        Flowable.__init__(self)
        self.width = width or (W - 80)
        self.height = 16

    def draw(self):
        c = self.canv
        c.setFillColor(C_LIGHT_GREEN)
        c.setStrokeColor(C_GREEN)
        c.setLineWidth(0.8)
        c.roundRect(0, 0, self.width, self.height, 4, fill=1, stroke=1)
        c.setFillColor(C_GREEN)
        c.setFont("Helvetica-Bold", 8)
        c.drawString(8, 4, "✅  ANSWER")


class SectionHeader(Flowable):
    """Big section divider."""
    def __init__(self, text, sub="", fill=C_DARK_BLUE, width=None):
        Flowable.__init__(self)
        self.text = text
        self.sub = sub
        self.fill = fill
        self.width = width or (W - 80)
        self.height = 42 if sub else 30

    def draw(self):
        c = self.canv
        c.setFillColor(self.fill)
        c.roundRect(0, 0, self.width, self.height, 7, fill=1, stroke=0)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 13)
        c.drawCentredString(self.width/2, self.height - 18, self.text)
        if self.sub:
            c.setFillColor(colors.HexColor("#93c5fd"))
            c.setFont("Helvetica", 8.5)
            c.drawCentredString(self.width/2, 6, self.sub)


class BetaOxFlowchart(Flowable):
    """Beta-oxidation flowchart as a Flowable."""
    def __init__(self, width=None):
        Flowable.__init__(self)
        self.width = width or (W - 80)
        self.height = 480

    def _arrow(self, c, x, y, length=16, color=C_GRAY):
        c.setStrokeColor(color)
        c.setFillColor(color)
        c.setLineWidth(1.4)
        c.line(x, y, x, y - length + 5)
        p = c.beginPath()
        p.moveTo(x, y - length)
        p.lineTo(x - 4, y - length + 7)
        p.lineTo(x + 4, y - length + 7)
        p.close()
        c.drawPath(p, fill=1, stroke=0)

    def _arrowr(self, c, x, y, length=20, color=C_GRAY):
        c.setStrokeColor(color)
        c.setFillColor(color)
        c.setLineWidth(1.4)
        c.line(x, y, x + length - 5, y)
        p = c.beginPath()
        p.moveTo(x + length, y)
        p.lineTo(x + length - 7, y + 4)
        p.lineTo(x + length - 7, y - 4)
        p.close()
        c.drawPath(p, fill=1, stroke=0)

    def _box(self, c, cx, y, w, h, label, sub="", fill=C_LIGHT_BLUE, stroke=C_BLUE):
        c.setFillColor(fill)
        c.setStrokeColor(stroke)
        c.setLineWidth(1)
        c.roundRect(cx - w/2, y - h, w, h, 6, fill=1, stroke=1)
        c.setFillColor(stroke)
        c.setFont("Helvetica-Bold", 8)
        if sub:
            c.drawCentredString(cx, y - h*0.35, label)
            c.setFillColor(C_GRAY)
            c.setFont("Helvetica", 7)
            c.drawCentredString(cx, y - h*0.72, sub)
        else:
            c.drawCentredString(cx, y - h*0.57, label)

    def _enz(self, c, x, y, text, color=C_ORANGE):
        c.setFillColor(color)
        c.setFont("Helvetica-Oblique", 6.5)
        c.drawString(x, y, text)

    def draw(self):
        c = self.canv
        CX = self.width / 2
        BW = 170
        BH = 30
        y = self.height - 5

        # Title
        c.setFillColor(C_DARK_BLUE)
        c.roundRect(0, y - 22, self.width, 22, 5, fill=1, stroke=0)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 10)
        c.drawCentredString(CX, y - 15, "β-OXIDATION FLOWCHART — Palmitic Acid (C16:0)")
        y -= 28

        # ACTIVATION
        c.setFillColor(C_LIGHT_AMBER)
        c.setStrokeColor(C_AMBER)
        c.setLineWidth(0.8)
        c.roundRect(0, y - 16, self.width, 16, 3, fill=1, stroke=1)
        c.setFillColor(colors.HexColor("#92400e"))
        c.setFont("Helvetica-Bold", 7.5)
        c.drawString(6, y - 11, "STEP 0 — ACTIVATION (Cytoplasm)")
        y -= 22

        self._box(c, CX, y, BW, BH, "Palmitic Acid (C16:0)", "Free fatty acid in cytoplasm",
                  fill=C_LIGHT_ORANGE, stroke=C_ORANGE)
        self._enz(c, CX + BW/2 + 4, y - 8, "Acyl CoA Synthetase")
        self._enz(c, CX + BW/2 + 4, y - 16, "ATP → AMP + PPi  (cost: 2 ATP)", color=C_RED)
        self._arrow(c, CX, y - BH, 18, C_ORANGE)
        y -= BH + 22

        self._box(c, CX, y, BW, BH, "Palmitoyl CoA", "Activated fatty acid",
                  fill=C_LIGHT_ORANGE, stroke=C_ORANGE)
        y -= BH + 8

        # CARNITINE SHUTTLE
        c.setFillColor(C_LIGHT_PURPLE)
        c.setStrokeColor(C_PURPLE)
        c.setLineWidth(0.8)
        c.roundRect(0, y - 16, self.width, 16, 3, fill=1, stroke=1)
        c.setFillColor(C_PURPLE)
        c.setFont("Helvetica-Bold", 7.5)
        c.drawString(6, y - 11, "CARNITINE SHUTTLE — Transport into Mitochondria")
        y -= 20

        sx = 10
        for i, (nm, nt) in enumerate([
            ("Palmitoyl CoA", "Outer membrane"),
            ("Palmitoyl-Carnitine", "CPT-I (rate-limiting)"),
            ("Palmitoyl CoA", "Matrix (CPT-II)")
        ]):
            self._box(c, sx + 75, y, 140, 26, nm, nt, fill=C_LIGHT_PURPLE, stroke=C_PURPLE)
            if i < 2:
                self._arrowr(c, sx + 145, y - 13, 18, C_PURPLE)
            sx += 158
        # malonyl CoA inhibition note
        c.setFillColor(C_RED)
        c.setFont("Helvetica-Bold", 6.5)
        c.drawString(6, y - 30, "⊗ CPT-I inhibited by Malonyl CoA (prevents futile cycling when FA synthesis is active)")
        y -= BH + 20

        # 4-STEP CYCLE
        c.setFillColor(C_LIGHT_GREEN)
        c.setStrokeColor(C_GREEN)
        c.setLineWidth(0.8)
        c.roundRect(0, y - 16, self.width, 16, 3, fill=1, stroke=1)
        c.setFillColor(C_GREEN)
        c.setFont("Helvetica-Bold", 7.5)
        c.drawString(6, y - 11, "β-OXIDATION CYCLE × 7  (4 reactions per cycle — Mitochondrial Matrix)")
        y -= 22

        steps4 = [
            ("① Dehydrogenation", "Acyl CoA\nDehydrogenase", "FAD→FADH₂", C_LIGHT_BLUE, C_BLUE),
            ("② Hydration", "Enoyl CoA\nHydratase", "+H₂O", C_LIGHT_GREEN, C_GREEN),
            ("③ Dehydrogenation", "3-OH Acyl CoA\nDehydrogenase", "NAD⁺→NADH", C_LIGHT_ORANGE, C_ORANGE),
            ("④ Thiolysis", "Beta-Ketothiolase", "+CoA→Acetyl CoA", C_LIGHT_PURPLE, C_PURPLE),
        ]
        bw4 = (self.width - 10) / 4 - 6
        sx4 = 5
        for i, (step, enz, cofactor, fill, stroke) in enumerate(steps4):
            c.setFillColor(fill)
            c.setStrokeColor(stroke)
            c.setLineWidth(1)
            c.roundRect(sx4, y - 44, bw4, 44, 5, fill=1, stroke=1)
            c.setFillColor(stroke)
            c.setFont("Helvetica-Bold", 7.5)
            c.drawCentredString(sx4 + bw4/2, y - 12, step)
            e_lines = enz.split("\n")
            c.setFillColor(C_DARK)
            c.setFont("Helvetica", 6.5)
            c.drawCentredString(sx4 + bw4/2, y - 23, e_lines[0])
            if len(e_lines) > 1:
                c.drawCentredString(sx4 + bw4/2, y - 31, e_lines[1])
            c.setFillColor(C_ORANGE)
            c.setFont("Helvetica-Bold", 6.5)
            c.drawCentredString(sx4 + bw4/2, y - 40, cofactor)
            if i < 3:
                self._arrowr(c, sx4 + bw4, y - 22, 6, stroke)
            sx4 += bw4 + 6

        y -= 52
        c.setFillColor(C_LIGHT_AMBER)
        c.setStrokeColor(C_AMBER)
        c.setLineWidth(0.8)
        c.roundRect(0, y - 16, self.width, 16, 4, fill=1, stroke=1)
        c.setFillColor(colors.HexColor("#92400e"))
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(CX, y - 10,
            "🔁  Repeat × 7  →  Products: 7 FADH₂  +  7 NADH  +  8 Acetyl CoA")
        y -= 22

        # ATP TABLE
        c.setFillColor(C_DARK_BLUE)
        c.roundRect(0, y - 16, self.width, 16, 3, fill=1, stroke=0)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 8)
        c.drawCentredString(CX, y - 11, "⚡  NET ATP YIELD")
        y -= 20

        rows = [
            ("Source", "Count", "ATP/unit", "Subtotal", True),
            ("8 × Acetyl CoA  →  TCA cycle", "8", "×10", "= 80", False),
            ("7 × NADH  →  ETC", "7", "×2.5", "= 17.5", False),
            ("7 × FADH₂  →  ETC", "7", "×1.5", "= 10.5", False),
            ("Activation cost  (ATP→AMP)", "—", "-2", "= -2", False),
            ("NET TOTAL ATP", "", "", "= 106 ATP ⭐", True),
        ]
        fills_atp = [C_BLUE, C_LIGHT_GREEN, C_LIGHT_BLUE, C_LIGHT_ORANGE, C_LIGHT_RED, C_DARK_BLUE]
        txt_cols = [C_WHITE, C_DARK, C_DARK, C_DARK, C_DARK, C_WHITE]
        col_xw = [(0, self.width*0.44), (self.width*0.44, self.width*0.14),
                  (self.width*0.58, self.width*0.17), (self.width*0.75, self.width*0.25)]
        for ri, (row, rf, tc) in enumerate(zip(rows, fills_atp, txt_cols)):
            rx = 0
            for ci, (val, (cx2, cw)) in enumerate(zip(row[:4], col_xw)):
                c.setFillColor(rf)
                c.setStrokeColor(colors.HexColor("#cbd5e1"))
                c.setLineWidth(0.5)
                c.rect(rx, y - 14, cw - 1, 14, fill=1, stroke=1)
                font = "Helvetica-Bold" if row[4] else "Helvetica"
                c.setFillColor(tc)
                c.setFont(font, 7.5 if ri > 0 else 8)
                c.drawCentredString(rx + cw/2, y - 9.5, val)
                rx += cw
            y -= 14


class CholSynthFlowchart(Flowable):
    """Cholesterol synthesis flowchart as a Flowable."""
    def __init__(self, width=None):
        Flowable.__init__(self)
        self.width = width or (W - 80)
        self.height = 500

    def _arrow(self, c, x, y, length=16, color=C_GREEN):
        c.setStrokeColor(color)
        c.setFillColor(color)
        c.setLineWidth(1.4)
        c.line(x, y, x, y - length + 5)
        p = c.beginPath()
        p.moveTo(x, y - length)
        p.lineTo(x - 4, y - length + 7)
        p.lineTo(x + 4, y - length + 7)
        p.close()
        c.drawPath(p, fill=1, stroke=0)

    def draw(self):
        c = self.canv
        CX = self.width / 2
        BW = 190
        BH = 30
        y = self.height - 5

        # Title
        c.setFillColor(C_GREEN)
        c.roundRect(0, y - 22, self.width, 22, 5, fill=1, stroke=0)
        c.setFillColor(C_WHITE)
        c.setFont("Helvetica-Bold", 10)
        c.drawCentredString(CX, y - 15, "CHOLESTEROL SYNTHESIS (de novo)")
        y -= 28

        # Stage headers + steps
        stages = [
            # (stage_hdr, steps_list)
            # steps: (label, sublabel, fill, stroke, enzyme, is_rate_limiting)
            ("STAGE 1 — HMG CoA Formation  (Cytosol / Mitochondria)", C_ORANGE, [
                ("Acetyl CoA  (2C)", "Starting material", C_LIGHT_ORANGE, C_ORANGE, None, False),
                ("Acetoacetyl CoA  (4C)", "2 Acetyl CoA condensed", C_LIGHT_ORANGE, C_ORANGE, "Thiolase", False),
                ("HMG CoA  (6C)", "3-Hydroxy-3-Methylglutaryl CoA", C_LIGHT_ORANGE, C_ORANGE, "HMG CoA Synthase", False),
            ]),
            ("STAGE 2 — Mevalonate Synthesis  ★ RATE-LIMITING", C_RED, [
                ("Mevalonate  (6C)", "★ RATE-LIMITING  |  Target of Statins", C_LIGHT_GREEN, C_GREEN,
                 "★ HMG CoA Reductase  (2 NADPH used)", True),
            ]),
            ("STAGE 3 — Activation & Decarboxylation  (Cytosol)", C_BLUE, [
                ("Mevalonate-5-Phosphate", "ATP used", C_LIGHT_BLUE, C_BLUE, "Mevalonate Kinase", False),
                ("Mevalonate-5-Pyrophosphate", "Second phosphorylation", C_LIGHT_BLUE, C_BLUE, "Phosphomevalonate Kinase", False),
                ("Isopentenyl-PP  (IPP, 5C)", "Active isoprene unit  |  CO₂ released", C_LIGHT_BLUE, C_BLUE,
                 "Mevalonate-PP Decarboxylase (ATP, CO₂↑)", False),
            ]),
            ("STAGE 4 — Squalene Synthesis", C_PURPLE, [
                ("Geranyl-PP (10C)  →  Farnesyl-PP (15C)", "2 IPP → GPP; 3 IPP → FPP", C_LIGHT_PURPLE, C_PURPLE,
                 "Geranyl / Farnesyl Transferases", False),
                ("Squalene  (30C)", "2 × FPP joined  (2 NADPH)", C_LIGHT_PURPLE, C_PURPLE,
                 "Squalene Synthase", False),
            ]),
            ("STAGE 5 — Ring Formation & Modifications  (SER)", C_TEAL, [
                ("Lanosterol  (30C)", "First sterol — ring cyclization", C_LIGHT_TEAL, C_TEAL,
                 "Squalene Monooxygenase + Cyclase (O₂, NADPH)", False),
                ("Cholesterol  (27C)", "Final product  |  ~19 steps, 3C lost", C_LIGHT_GREEN, C_GREEN,
                 "Multiple demethylation/reduction enzymes", False),
            ]),
        ]

        for stage_label, stage_color, steps in stages:
            # Stage header
            c.setFillColor(stage_color)
            c.roundRect(0, y - 16, self.width, 16, 3, fill=1, stroke=0)
            c.setFillColor(C_WHITE)
            c.setFont("Helvetica-Bold", 7.5)
            c.drawString(6, y - 11, stage_label)
            y -= 20

            for (lbl, sub, fill, stroke, enz, is_rl) in steps:
                # Enzyme label + arrow
                if enz:
                    enz_color = C_RED if is_rl else C_ORANGE
                    c.setFillColor(enz_color)
                    c.setFont("Helvetica-Bold" if is_rl else "Helvetica-Oblique", 6.5)
                    c.drawCentredString(CX + BW/2 + 45, y - 5, enz)
                    self._arrow(c, CX, y, 14, C_GREEN)
                    y -= 17

                # Compound box
                c.setFillColor(fill)
                c.setStrokeColor(stroke)
                c.setLineWidth(1.2 if is_rl else 0.8)
                c.roundRect(CX - BW/2, y - BH, BW, BH, 6, fill=1, stroke=1)
                c.setFillColor(stroke)
                c.setFont("Helvetica-Bold", 8)
                c.drawCentredString(CX, y - BH*0.38, lbl)
                c.setFillColor(C_GRAY)
                c.setFont("Helvetica", 6.5)
                c.drawCentredString(CX, y - BH*0.75, sub)
                y -= BH + 2

            y -= 4

        # Downstream products note
        c.setFillColor(C_LIGHT_AMBER)
        c.setStrokeColor(C_AMBER)
        c.setLineWidth(0.8)
        c.roundRect(0, y - 22, self.width, 22, 5, fill=1, stroke=1)
        c.setFillColor(C_AMBER)
        c.setFont("Helvetica-Bold", 8)
        c.drawString(6, y - 9, "Other products of Mevalonate pathway:")
        c.setFillColor(C_DARK)
        c.setFont("Helvetica", 7)
        c.drawString(6, y - 18,
            "Dolichol (protein glycosylation)  ·  Ubiquinone (ETC)  ·  Isoprenoids  ·  Farnesyl groups (protein prenylation)")


# ════════════════════════════════════════════════════════════════
#  STYLES
# ════════════════════════════════════════════════════════════════
styles = getSampleStyleSheet()

def S(name, **kw):
    """Create a ParagraphStyle."""
    return ParagraphStyle(name, **kw)

sNormal = S("MyNormal", fontName="Helvetica", fontSize=8.5, leading=13,
            textColor=C_DARK, spaceAfter=4)
sBold   = S("MyBold", fontName="Helvetica-Bold", fontSize=8.5, leading=13,
            textColor=C_DARK, spaceAfter=4)
sBody   = S("MyBody", fontName="Helvetica", fontSize=8.5, leading=13.5,
            textColor=C_DARK, spaceAfter=3, leftIndent=6)
sPoint  = S("MyPoint", fontName="Helvetica", fontSize=8.5, leading=13,
            textColor=C_DARK, spaceAfter=2, leftIndent=14)
sSubHdr = S("MySubHdr", fontName="Helvetica-Bold", fontSize=9, leading=14,
            textColor=C_DARK_BLUE, spaceAfter=3, spaceBefore=5)
sNote   = S("MyNote", fontName="Helvetica-Oblique", fontSize=7.5, leading=11,
            textColor=C_GRAY, spaceAfter=3)
sTableHdr = S("TH", fontName="Helvetica-Bold", fontSize=8, leading=10,
              textColor=C_WHITE, alignment=TA_CENTER)
sTableCell= S("TC", fontName="Helvetica", fontSize=7.5, leading=10,
              textColor=C_DARK, alignment=TA_LEFT)
sTableCellB=S("TCB", fontName="Helvetica-Bold", fontSize=7.5, leading=10,
              textColor=C_DARK, alignment=TA_LEFT)


def p(text, style=None):
    return Paragraph(text, style or sBody)

def sp(h=4):
    return Spacer(1, h)

def hr(color=C_LIGHT_GRAY):
    return HRFlowable(width="100%", thickness=1, color=color, spaceAfter=4, spaceBefore=4)


def make_table(headers, rows, col_widths, hdr_fill=C_BLUE):
    data = [[Paragraph(h, sTableHdr) for h in headers]]
    for row in rows:
        data.append([Paragraph(str(cell), sTableCell) for cell in row])
    t = Table(data, colWidths=col_widths)
    style_cmds = [
        ('BACKGROUND', (0, 0), (-1, 0), hdr_fill),
        ('TEXTCOLOR',  (0, 0), (-1, 0), C_WHITE),
        ('ROWBACKGROUNDS', (0, 1), (-1, -1), [C_LIGHT_GRAY, C_WHITE]),
        ('GRID', (0, 0), (-1, -1), 0.5, colors.HexColor("#cbd5e1")),
        ('VALIGN', (0, 0), (-1, -1), 'MIDDLE'),
        ('TOPPADDING', (0, 0), (-1, -1), 4),
        ('BOTTOMPADDING', (0, 0), (-1, -1), 4),
        ('LEFTPADDING', (0, 0), (-1, -1), 5),
        ('RIGHTPADDING', (0, 0), (-1, -1), 5),
        ('FONTSIZE', (0, 0), (-1, 0), 8),
    ]
    t.setStyle(TableStyle(style_cmds))
    return t


# ════════════════════════════════════════════════════════════════
#  PAGE TEMPLATE (header / footer on every page)
# ════════════════════════════════════════════════════════════════
PAGE_NUM = [0]

def on_page(canvas, doc):
    PAGE_NUM[0] += 1
    canvas.saveState()
    # Header strip
    canvas.setFillColor(C_DARK_BLUE)
    canvas.rect(0, H - 28, W, 28, fill=1, stroke=0)
    canvas.setFillColor(C_WHITE)
    canvas.setFont("Helvetica-Bold", 8.5)
    canvas.drawString(20, H - 18, "MBBS 1st Year Biochemistry  ·  Lipid Chemistry & Metabolism  ·  PYQ Guide")
    canvas.setFillColor(C_YELLOW)
    canvas.setFont("Helvetica-Bold", 8)
    canvas.drawRightString(W - 20, H - 18, f"Page {PAGE_NUM[0]}")
    # Footer strip
    canvas.setFillColor(C_LIGHT_GRAY)
    canvas.rect(0, 0, W, 18, fill=1, stroke=0)
    canvas.setFillColor(C_GRAY)
    canvas.setFont("Helvetica", 6.5)
    canvas.drawCentredString(W/2, 5,
        "Sources: WBUHS PYQ Bank 2010–2023  ·  Lippincott's Illustrated Reviews Biochemistry 8e  ·  Harper's Illustrated Biochemistry")
    canvas.restoreState()


# ════════════════════════════════════════════════════════════════
#  BUILD CONTENT
# ════════════════════════════════════════════════════════════════
story = []
SP = sp

# ─── COVER ────────────────────────────────────────────────────
# (cover is page 1, drawn in on_page header)
story.append(sp(30))
story.append(SectionHeader(
    "LIPID CHEMISTRY & METABOLISM",
    sub="Complete PYQ Guide with Answers & Flowcharts  ·  MBBS 1st Year Biochemistry",
    fill=C_DARK_BLUE))
story.append(sp(10))
story.append(SectionHeader("MBBS 1st Year — University Exam 2013–2023",
                            sub="WBUHS & Other Indian Universities",
                            fill=C_BLUE))
story.append(sp(12))

toc_data = [
    ["Section", "Topics Covered", "Page"],
    ["A. Long Answer (LAQ)", "Beta-oxidation · Cholesterol synthesis · FA synthesis · VLDL", "2–5"],
    ["B. Short Notes (SN)", "Ketone bodies · Lipoproteins · Phospholipids · Fatty liver", "5–8"],
    ["C. Explain the Reason (EQ)", "Fat→Glucose · Beta-ox → Hypoglycemia", "8–9"],
    ["D. Flowchart: Beta-Oxidation", "Step-by-step with ATP table", "10"],
    ["E. Flowchart: Cholesterol", "HMG CoA → Cholesterol pathway", "11"],
    ["F. High-Yield Summary Table", "Comparison, disorders, exam tips", "12"],
]
story.append(make_table(
    ["Section", "Topics Covered", "Page"],
    toc_data[1:],
    [120, 270, 50],
    hdr_fill=C_DARK_BLUE
))
story.append(sp(8))

# Frequency chart
freq = [
    ("Beta-oxidation + ATP calculation", "★★★★★", "2013,15,17,18,19,20,21,22"),
    ("Cholesterol synthesis + HMG CoA reductase", "★★★★★", "2013–2023 almost every year"),
    ("Ketone bodies", "★★★★★", "2010,12,14,15,16,17,18,19,20,21"),
    ("Lipoproteins / VLDL / RCT", "★★★★", "2011,13,14,15,16,17,18,19,20"),
    ("Fatty acid synthesis / FAS complex", "★★★★", "2014,15,16,17,18,19,21"),
    ("Phospholipids / Lecithin / Phospholipases", "★★★", "2010,13,18,19,22"),
    ("Fatty liver + Lipotropic factors", "★★★", "2012,14,16,18,20"),
    ("Essential fatty acids", "★★★", "2010,13,14,15,17,19"),
]
story.append(SectionHeader("⭐ FREQUENCY TABLE — Most Repeated Topics", fill=C_AMBER))
story.append(sp(4))
story.append(make_table(
    ["Topic", "Frequency", "Exam Years"],
    freq,
    [200, 70, 170],
    hdr_fill=C_AMBER
))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION A: LONG ANSWER QUESTIONS
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION A — LONG ANSWER QUESTIONS (LAQ)  |  10–12 Marks",
                            sub="Essay-type questions requiring detailed answers with diagrams",
                            fill=C_DARK_BLUE))
story.append(sp(8))

# ── Q1 Beta-oxidation ─────────────────────────────────────────
story.append(QuestionBox("Q1",
    "Describe beta-oxidation of palmitic acid. Calculate net ATP. How does oxidation of oleic acid differ?",
    "[8+2+2]", "WBUHS 2017-S, 2015, 2019, 2020"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>BETA-OXIDATION OF PALMITIC ACID (C16:0)</b>", sSubHdr))
story.append(p("Beta-oxidation is the major pathway for oxidation of fatty acids. It occurs in the <b>mitochondrial matrix</b>. Palmitic acid (16 carbons) undergoes <b>7 cycles</b> to yield <b>8 Acetyl CoA</b>.", sBody))
story.append(sp(4))

story.append(p("<b>Step 0 — Activation (Cytoplasm):</b>", sBold))
story.append(p("Palmitate + CoA + ATP → Palmitoyl CoA + AMP + PPi  (catalysed by Acyl CoA Synthetase / Thiokinase)", sBody))
story.append(p("Cost = 2 ATP equivalents (ATP → AMP = 2 high-energy bonds broken)", sPoint))

story.append(p("<b>Carnitine Shuttle (transport across inner mitochondrial membrane):</b>", sBold))
story.append(p("• Palmitoyl CoA + Carnitine → Palmitoyl-Carnitine  (CPT-I, outer membrane)", sPoint))
story.append(p("• Palmitoyl-Carnitine crosses via Translocase (antiport with free carnitine)", sPoint))
story.append(p("• Palmitoyl-Carnitine + CoA → Palmitoyl CoA + Carnitine  (CPT-II, inner membrane)", sPoint))
story.append(p("• <b>CPT-I is the rate-limiting step</b> — inhibited by <b>Malonyl CoA</b> (prevents futile cycling)", sPoint))

story.append(sp(4))
story.append(p("<b>4 Reactions of Each Beta-Oxidation Cycle:</b>", sBold))
story.append(make_table(
    ["Step", "Reaction", "Enzyme", "Coenzyme/Product"],
    [
        ["① Dehydrogenation", "Acyl CoA → Trans-2-Enoyl CoA", "Acyl CoA Dehydrogenase", "FAD → FADH₂"],
        ["② Hydration", "Enoyl CoA → L-3-Hydroxyacyl CoA", "Enoyl CoA Hydratase", "H₂O added"],
        ["③ Dehydrogenation", "Hydroxyacyl CoA → 3-Ketoacyl CoA", "3-OH Acyl CoA Dehydrogenase", "NAD⁺ → NADH"],
        ["④ Thiolysis", "Ketoacyl CoA → Acetyl CoA + shortened acyl CoA", "Beta-Ketothiolase", "CoA-SH consumed"],
    ],
    [55, 155, 130, 100],
    hdr_fill=C_BLUE
))
story.append(sp(4))

story.append(p("<b>ATP Calculation:</b>", sBold))
story.append(make_table(
    ["Source", "Count", "ATP/unit", "Subtotal"],
    [
        ["8 × Acetyl CoA → TCA cycle", "8", "× 10", "= 80"],
        ["7 × NADH → ETC (P/O ratio 2.5)", "7", "× 2.5", "= 17.5"],
        ["7 × FADH₂ → ETC (P/O ratio 1.5)", "7", "× 1.5", "= 10.5"],
        ["Activation cost (ATP → AMP = 2 bonds)", "1", "−2", "= −2"],
    ],
    [200, 60, 80, 100],
    hdr_fill=C_GREEN
))
story.append(p("<b>Net ATP from Palmitic Acid = 80 + 17.5 + 10.5 − 2 = 106 ATP</b>", sSubHdr))
story.append(sp(4))

story.append(p("<b>Difference for Oleic Acid (C18:1, Δ9):</b>", sBold))
story.append(p("• After 3 normal beta-oxidation cycles, a <b>cis-3-enoyl CoA</b> intermediate is produced", sPoint))
story.append(p("• Extra enzyme needed: <b>3,2-Enoyl CoA Isomerase</b> converts cis-3 to trans-2 derivative", sPoint))
story.append(p("• This isomerase step bypasses the Acyl CoA Dehydrogenase step → <b>1 FADH₂ not produced</b>", sPoint))
story.append(p("• Net ATP for oleic acid ≈ 106 − 1.5 = <b>~104.5 ATP</b> (approximately 2 ATP less than palmitate)", sPoint))
story.append(p("• Linoleic acid (C18:2, Δ9,12) needs both the isomerase AND an NADPH-dependent 2,4-dienoyl CoA reductase → even fewer ATP", sPoint))
story.append(sp(6))
story.append(hr())

# ── Q2 Cholesterol Synthesis ───────────────────────────────────
story.append(QuestionBox("Q2",
    "Describe biosynthesis of cholesterol. Name regulatory enzyme. Explain reverse cholesterol transport.",
    "[8+2+2]", "WBUHS 2013–2023 (Most frequent)"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>CHOLESTEROL SYNTHESIS (de novo)</b>", sSubHdr))
story.append(p("• All 27 carbons derived from <b>Acetyl CoA</b> | Site: mainly <b>liver</b>, also intestine, adrenal, gonads", sBody))
story.append(p("• Location: Cytosol + Smooth Endoplasmic Reticulum (SER)", sBody))
story.append(sp(4))

chol_steps = [
    ["Stage 1 — HMG CoA", "2 Acetyl CoA → Acetoacetyl CoA (Thiolase)\nAcetoacetyl CoA + Acetyl CoA → HMG CoA (HMG CoA Synthase)", "Cytosol / Mitochondria"],
    ["Stage 2 — Mevalonate ★", "HMG CoA + 2NADPH → Mevalonate\n★ HMG CoA Reductase (RATE-LIMITING)", "Cytosol (ER membrane)"],
    ["Stage 3 — Activation", "Mevalonate → Mevalonate-5-P → Mevalonate-5-PP\n→ Isopentenyl-PP (IPP, 5C) + CO₂", "Cytosol"],
    ["Stage 4 — Squalene", "3 IPP → Farnesyl-PP (15C)\n2 Farnesyl-PP → Squalene (30C) by Squalene Synthase", "Cytosol"],
    ["Stage 5 — Cholesterol", "Squalene → Lanosterol (ring cyclization, O₂ needed)\nLanosterol → Cholesterol (~19 steps, 3C lost)", "SER"],
]
story.append(make_table(
    ["Stage", "Key Reactions", "Location"],
    chol_steps,
    [100, 240, 100],
    hdr_fill=C_GREEN
))
story.append(sp(4))

story.append(p("<b>Regulatory Enzyme — HMG CoA Reductase:</b>", sBold))
story.append(p("• <b>Rate-limiting enzyme</b> of cholesterol synthesis", sPoint))
story.append(p("• <b>Activated by:</b> Insulin, Thyroid hormone (T3)", sPoint))
story.append(p("• <b>Inhibited by:</b> High cholesterol (via SREBP↓), Glucagon, Glucocorticoids", sPoint))
story.append(p("• <b>Statins</b> (e.g., Atorvastatin, Rosuvastatin) = competitive inhibitors → ↓ LDL cholesterol", sPoint))
story.append(p("• SREBP (Sterol Regulatory Element Binding Protein): when cholesterol is low, SREBP is activated → increases HMG CoA reductase expression", sPoint))
story.append(sp(4))

story.append(p("<b>Reverse Cholesterol Transport (RCT):</b>", sBold))
story.append(p("Process by which excess cholesterol is returned from <b>peripheral tissues → liver</b> for excretion.", sBody))
story.append(make_table(
    ["Step", "Process", "Key Player"],
    [
        ["1", "Lipid-poor ApoA-I (nascent HDL) picks up free cholesterol from peripheral cells", "ABCA1 transporter"],
        ["2", "Free cholesterol esterified on HDL surface (HDL3 → HDL2)", "LCAT enzyme"],
        ["3", "Some CE transferred from HDL to LDL/VLDL in exchange for TGs", "CETP (Cholesteryl Ester Transfer Protein)"],
        ["4", "Liver selectively takes up cholesterol esters from mature HDL", "SR-B1 receptor"],
        ["5", "Cholesterol → Bile acids → Excreted in bile", "Liver enzymes"],
    ],
    [30, 260, 140],
    hdr_fill=C_TEAL
))
story.append(p("<b>Clinical:</b> Low HDL = impaired RCT = increased atherosclerosis risk. HDL is called 'good cholesterol'.", sNote))
story.append(sp(6))
story.append(hr())

# ── Q3 Fatty Acid Synthesis ────────────────────────────────────
story.append(QuestionBox("Q3",
    "Describe de novo fatty acid synthesis. Name enzymes of fatty acid synthase complex.",
    "[10+2]", "WBUHS 2014–2021"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>FATTY ACID SYNTHESIS (de novo)</b>", sSubHdr))
story.append(p("Occurs in <b>cytosol</b>. Requires <b>NADPH</b> (from PPP + malic enzyme) and HCO₃⁻. Main product = <b>Palmitate (C16:0)</b>. Site: liver and adipose tissue.", sBody))
story.append(sp(4))

story.append(p("<b>Step 1 — Carboxylation (Rate-limiting step):</b>", sBold))
story.append(p("Acetyl CoA + CO₂ + ATP → <b>Malonyl CoA</b>  (via <b>Acetyl CoA Carboxylase, ACC</b>)", sBody))
story.append(p("• ACC is the <b>rate-limiting enzyme</b> of FA synthesis", sPoint))
story.append(p("• <b>Activated by:</b> Citrate, Insulin | <b>Inhibited by:</b> Palmitoyl CoA, Glucagon, AMPK", sPoint))
story.append(sp(4))

story.append(p("<b>Fatty Acid Synthase (FAS) Complex — 7 Domains:</b>", sBold))
story.append(make_table(
    ["Domain / Enzyme", "Function", "Notes"],
    [
        ["ACP (Acyl Carrier Protein)", "Carries growing fatty acid chain", "4'-phosphopantetheine as prosthetic group"],
        ["Acetyl Transacylase", "Transfers acetyl group to Cys-SH of KS", "Primer loading"],
        ["Malonyl Transacylase", "Transfers malonyl to ACP-SH", "Extender loading"],
        ["Beta-Ketoacyl Synthase (condensing enz.)", "Condensation — releases CO₂", "C-C bond formation"],
        ["Beta-Ketoacyl Reductase", "Reduction of keto group", "Uses NADPH"],
        ["Beta-Hydroxyacyl Dehydratase", "Dehydration", "Removes H₂O"],
        ["Enoyl Reductase", "Final reduction", "Uses NADPH"],
        ["Thioesterase", "Releases palmitate from ACP", "After 7 elongation cycles"],
    ],
    [145, 150, 145],
    hdr_fill=C_PURPLE
))
story.append(sp(4))
story.append(p("<b>Each elongation cycle uses:</b> 1 Malonyl CoA + 2 NADPH | 7 cycles → Palmitate (C16)", sBody))
story.append(p("<b>Overall equation:</b> 8 Acetyl CoA + 7 ATP + 14 NADPH → Palmitate + 8 CoA + 7 ADP + 7 Pi + 14 NADP⁺ + 6 H₂O", sNote))
story.append(sp(6))
story.append(hr())

# ── Q4 VLDL ──────────────────────────────────────────────────
story.append(QuestionBox("Q4",
    "Write the metabolism of VLDL. Explain reverse cholesterol transport.",
    "[8+4]", "WBUHS 2013–2020"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>VLDL (Very Low Density Lipoprotein) METABOLISM</b>", sSubHdr))
story.append(p("VLDL = endogenous lipid transport vehicle | Carries TG made in <b>liver</b> to peripheral tissues", sBody))
story.append(sp(4))

story.append(make_table(
    ["Step", "Event", "Enzyme/Receptor"],
    [
        ["1. Synthesis", "Liver assembles TG + Cholesterol + ApoB-100 + ApoC-II + ApoE → VLDL particle", "MTP (Microsomal Triglyceride Transfer Protein)"],
        ["2. Secretion", "VLDL secreted into blood via Golgi", "—"],
        ["3. TG Hydrolysis", "In capillaries of muscle/adipose: TG hydrolysed → FFAs enter cells", "LPL (activated by ApoC-II)"],
        ["4. VLDL → IDL", "VLDL loses TG → becomes denser IDL (remnant)", "—"],
        ["5. IDL fate (50%)", "Taken up by liver via LDL receptor (ApoE recognition)", "LDL receptor"],
        ["6. IDL → LDL (50%)", "Remaining IDL: TG further removed → LDL (most cholesterol-rich)", "Hepatic Lipase"],
        ["7. LDL clearance", "LDL taken up by liver/tissues via LDL receptor (ApoB-100 ligand)", "LDL receptor"],
    ],
    [55, 220, 155],
    hdr_fill=C_BLUE
))
story.append(sp(4))
story.append(p("<b>VLDL → IDL → LDL</b> is the key cascade. LDL is the main cholesterol carrier in blood.", sBody))
story.append(p("<b>Clinical:</b> Elevated VLDL → hypertriglyceridemia. Elevated LDL → atherosclerosis. Familial hypercholesterolemia = defective LDL receptor.", sNote))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION B: SHORT NOTES
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION B — SHORT NOTES (SN)  |  5–7 Marks",
                            sub="Brief but complete answers required",
                            fill=C_TEAL))
story.append(sp(8))

# ── SN1: Ketone Bodies ────────────────────────────────────────
story.append(QuestionBox("SN1",
    "Ketone bodies — formation, utilization, and clinical significance (Diabetic Ketoacidosis)",
    "[5–7 marks]", "WBUHS 2010–2022 (Very frequent)"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>Ketone Bodies:</b> Acetoacetate, Beta-hydroxybutyrate (BHB), Acetone", sSubHdr))
story.append(p("<b>Site of Formation (Ketogenesis):</b> Liver mitochondria only", sBody))
story.append(p("<b>When formed?</b> Starvation, T1 Diabetes, high-fat diet → excess Acetyl CoA exceeds TCA cycle capacity", sBody))
story.append(sp(3))

story.append(p("<b>Steps of Ketogenesis:</b>", sBold))
story.append(make_table(
    ["Step", "Reaction", "Enzyme"],
    [
        ["1", "2 Acetyl CoA → Acetoacetyl CoA", "Thiolase"],
        ["2", "Acetoacetyl CoA + Acetyl CoA → HMG CoA (6C)", "HMG CoA Synthase (mitochondrial)"],
        ["3", "HMG CoA → Acetoacetate + Acetyl CoA  ← KEY STEP", "HMG CoA Lyase"],
        ["4", "Acetoacetate + NADH → Beta-hydroxybutyrate", "BHB Dehydrogenase"],
        ["5", "Acetoacetate → Acetone + CO₂  (spontaneous)", "Spontaneous decarboxylation"],
    ],
    [30, 230, 170],
    hdr_fill=C_ORANGE
))
story.append(sp(3))

story.append(p("<b>Utilization (Ketolysis — in extrahepatic tissues: brain, heart, muscle, kidney):</b>", sBold))
story.append(p("• BHB → Acetoacetate (BHB dehydrogenase, NAD⁺)", sPoint))
story.append(p("• Acetoacetate + Succinyl CoA → Acetoacetyl CoA + Succinate (via Succinyl CoA Transferase / Thiophorase)", sPoint))
story.append(p("• Acetoacetyl CoA → 2 Acetyl CoA → TCA → ATP", sPoint))
story.append(p("• <b>Liver CANNOT use ketone bodies</b> — it lacks succinyl CoA transferase (thiophorase)", sPoint))
story.append(sp(3))

story.append(p("<b>Diabetic Ketoacidosis (DKA):</b>", sBold))
story.append(p("• In T1D: absent insulin → unrestrained lipolysis (HSL active) + excess glucagon", sPoint))
story.append(p("• Massive FFA release → flood liver with Acetyl CoA → excessive ketogenesis", sPoint))
story.append(p("• Blood ketones ↑ → metabolic acidosis → pH falls", sPoint))
story.append(p("• Signs: Kussmaul breathing, fruity breath (acetone), ketonuria, glycosuria, dehydration", sPoint))
story.append(p("• Treatment: Insulin + IV fluids + electrolyte correction", sPoint))
story.append(sp(6))
story.append(hr())

# ── SN2: Lipoproteins ──────────────────────────────────────────
story.append(QuestionBox("SN2",
    "Classify lipoproteins. Write composition, functions, and clinical significance.",
    "[5–7 marks]", "WBUHS 2011–2023"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(make_table(
    ["Lipoprotein", "Density", "TG %", "Chol %", "Apo-protein", "Function"],
    [
        ["Chylomicron", "<0.95", "85%", "5%", "ApoB-48, ApoC-II, ApoE", "Transport dietary (exogenous) TG from gut"],
        ["VLDL", "0.95–1.006", "55%", "15%", "ApoB-100, ApoC-II, ApoE", "Transport endogenous TG from liver"],
        ["IDL", "1.006–1.019", "31%", "22%", "ApoB-100, ApoE", "Intermediate in VLDL→LDL conversion"],
        ["LDL", "1.019–1.063", "10%", "45%", "ApoB-100", "Deliver cholesterol to tissues; atherogenic"],
        ["HDL", "1.063–1.21", "5%", "20%", "ApoA-I, ApoA-II", "Reverse cholesterol transport; protective"],
    ],
    [65, 55, 35, 40, 125, 120],
    hdr_fill=C_BLUE
))
story.append(sp(3))
story.append(p("<b>Key Enzymes:</b>", sBold))
story.append(p("• <b>LPL</b> (Lipoprotein Lipase): hydrolyzes TG in chylomicrons/VLDL on capillary endothelium; activated by ApoC-II; inhibited by ApoC-III", sPoint))
story.append(p("• <b>LCAT</b> (Lecithin-Cholesterol Acyl Transferase): esterifies free cholesterol in HDL; activated by ApoA-I", sPoint))
story.append(p("• <b>CETP</b>: transfers CE from HDL to LDL/VLDL in exchange for TG", sPoint))
story.append(p("• <b>Hepatic Lipase</b>: removes TG from IDL → LDL; removes TG from HDL2 → HDL3", sPoint))
story.append(sp(6))
story.append(hr())

# ── SN3: Phospholipids ────────────────────────────────────────
story.append(QuestionBox("SN3",
    "Classify phospholipids with examples. Draw structure of lecithin. Write action of phospholipases.",
    "[10+2] or [3+1+4+4]", "WBUHS 2013, 2018, 2019-S"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>Classification of Phospholipids:</b>", sSubHdr))
story.append(p("<b>A. Glycerophospholipids</b> (glycerol backbone):", sBold))
story.append(make_table(
    ["Phospholipid", "Head Group", "Location / Function"],
    [
        ["Phosphatidylcholine (Lecithin)", "Choline", "Most abundant; RBC membrane; pulmonary surfactant"],
        ["Phosphatidylethanolamine (Cephalin)", "Ethanolamine", "Inner leaflet cell membranes; blood clotting"],
        ["Phosphatidylserine", "Serine", "Inner leaflet; apoptosis signal when exposed"],
        ["Phosphatidylinositol", "Inositol", "Second messenger (IP₃ pathway); inner leaflet"],
        ["Cardiolipin", "Glycerol+phosphate", "Inner mitochondrial membrane; ETC function"],
        ["Plasmalogen", "Ether-linked FA", "Heart, brain; antioxidant function"],
    ],
    [145, 80, 215],
    hdr_fill=C_PURPLE
))
story.append(sp(3))
story.append(p("<b>B. Sphingophospholipids:</b> Sphingomyelin — sphingosine backbone; in myelin sheath and cell membranes", sBody))
story.append(sp(3))

story.append(p("<b>Structure of Lecithin (Phosphatidylcholine):</b>", sBold))
story.append(p("• sn-1 position: Saturated FA (e.g., palmitate, 16:0) — ester bond to glycerol C1", sPoint))
story.append(p("• sn-2 position: Unsaturated FA (e.g., arachidonate, 20:4) — ester bond to glycerol C2", sPoint))
story.append(p("• sn-3 position: Phosphocholine head group — phosphodiester bond to glycerol C3", sPoint))
story.append(sp(3))

story.append(p("<b>Phospholipases — Action on Lecithin:</b>", sBold))
story.append(make_table(
    ["Enzyme", "Bond Cleaved", "Products", "Significance"],
    [
        ["Phospholipase A1", "Ester at sn-1", "Free FA (sn-1) + 2-lysophospholipid", "Digestion"],
        ["Phospholipase A2", "Ester at sn-2", "Free FA (sn-2) + 1-lysophospholipid", "Releases arachidonic acid → eicosanoids; activated in inflammation"],
        ["Phospholipase B (Lysophospholipase)", "Ester at sn-1 or sn-2 on lyso-PL", "Glycerophosphocholine + FA", "Digestion of lyso-phospholipids"],
        ["Phospholipase C", "Glycerol-phosphate bond", "DAG + phosphocholine", "Signal transduction (IP₃/DAG pathway)"],
        ["Phospholipase D", "Phosphate-head group bond", "Phosphatidic acid + choline", "Signal transduction"],
    ],
    [90, 90, 120, 140],
    hdr_fill=C_TEAL
))
story.append(sp(6))
story.append(hr())

# ── SN4: Fatty Liver ─────────────────────────────────────────
story.append(QuestionBox("SN4",
    "Fatty liver and lipotropic factors",
    "[5 marks]", "WBUHS 2012–2020"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>Fatty Liver (Hepatic Steatosis):</b>", sSubHdr))
story.append(p("Accumulation of >5% TG in liver by weight. Normal liver contains <5% lipid.", sBody))
story.append(sp(3))
story.append(p("<b>Causes:</b>", sBold))
story.append(make_table(
    ["Cause", "Mechanism"],
    [
        ["Excess FFA delivery", "Obesity, DM, starvation → ↑ lipolysis → ↑ FFA to liver"],
        ["Increased TG synthesis", "↑ glucose → ↑ Acetyl CoA → ↑ FA synthesis → ↑ TG"],
        ["↓ VLDL secretion (most common)", "Choline/protein deficiency → impaired apolipoprotein/phospholipid for VLDL assembly"],
        ["Alcohol (most common cause)", "↑ NADH → diverts OAA from gluconeogenesis; inhibits FAO; ↑ TG synthesis"],
        ["CCl₄ poisoning", "Inhibits VLDL secretion (damages smooth ER)"],
    ],
    [140, 300],
    hdr_fill=C_RED
))
story.append(sp(3))

story.append(p("<b>Lipotropic Factors</b> (promote fat removal from liver by enhancing VLDL synthesis):", sBold))
story.append(make_table(
    ["Factor", "Role"],
    [
        ["Choline (most important)", "Provides phosphocholine for phosphatidylcholine synthesis → needed for VLDL assembly"],
        ["Methionine", "Methyl donor for choline synthesis via transmethylation; also provides S-adenosylmethionine"],
        ["Inositol", "For phosphatidylinositol synthesis (membrane component of VLDL)"],
        ["Betaine", "Alternate methyl donor; choline precursor"],
        ["Vitamin B12 + Folate", "Needed for methyl transfer reactions in choline synthesis"],
    ],
    [140, 300],
    hdr_fill=C_GREEN
))
story.append(sp(6))
story.append(hr())

# ── SN5: Essential Fatty Acids ────────────────────────────────
story.append(QuestionBox("SN5",
    "Essential fatty acids — definition, examples, functions, deficiency",
    "[5 marks]", "WBUHS 2010–2022"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))

story.append(p("<b>Definition:</b> Fatty acids that cannot be synthesised in the body (lack Δ9 desaturase beyond C9 in humans) and must be supplied in diet.", sBody))
story.append(sp(3))
story.append(make_table(
    ["EFA", "Structure", "Family", "Dietary Source", "Derivative"],
    [
        ["Linoleic acid", "18:2 (Δ9,12)", "Omega-6 (ω-6)", "Sunflower, corn, soybean oil", "Arachidonic acid (20:4, Δ5,8,11,14)"],
        ["Alpha-linolenic acid", "18:3 (Δ9,12,15)", "Omega-3 (ω-3)", "Flaxseed, fish oil, walnuts", "EPA (20:5) and DHA (22:6)"],
    ],
    [80, 85, 60, 120, 95],
    hdr_fill=C_ORANGE
))
story.append(sp(3))
story.append(p("<b>Functions:</b>", sBold))
story.append(p("1. Structural component of cell membranes — maintain fluidity (especially DHA in brain/retina)", sPoint))
story.append(p("2. Precursors of <b>eicosanoids</b> (arachidonic acid → Prostaglandins, Thromboxanes, Leukotrienes via COX and LOX)", sPoint))
story.append(p("3. Required for <b>skin integrity</b> (maintain permeability barrier)", sPoint))
story.append(p("4. Needed for normal growth, development, reproduction", sPoint))
story.append(p("5. Transport cholesterol as cholesterol esters (linoleic acid used by LCAT)", sPoint))
story.append(sp(3))
story.append(p("<b>Deficiency signs:</b> Scaly dermatitis, poor wound healing, impaired growth, increased susceptibility to infections, abnormal liver function", sBody))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION C: EXPLAIN THE REASON (EQ)
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION C — EXPLAIN THE REASON (EQ Questions)  |  2–3 Marks",
                            sub="Write biochemical justification clearly",
                            fill=C_PURPLE))
story.append(sp(8))

# EQ1
story.append(QuestionBox("EQ1",
    "Fat can be synthesized from glucose, but glucose cannot be synthesized from fat.",
    "[2–3 marks]", "WBUHS — Repeated multiple times"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))
story.append(p("• Glucose → Pyruvate (glycolysis) → Acetyl CoA (by <b>Pyruvate Dehydrogenase</b> — IRREVERSIBLE)", sPoint))
story.append(p("• Acetyl CoA can enter FA synthesis → fats are formed <b>(glucose → fat is possible ✓)</b>", sPoint))
story.append(p("• Acetyl CoA <b>cannot be converted back to Pyruvate</b> — no reverse pyruvate dehydrogenase in mammals", sPoint))
story.append(p("• Acetyl CoA cannot provide net carbon for gluconeogenesis (enters TCA but OAA is not increased net)", sPoint))
story.append(p("• Therefore fat (as Acetyl CoA) <b>cannot generate glucose net</b> in mammals <b>(fat → glucose is NOT possible ✗)</b>", sPoint))
story.append(p("• Exception: Glycerol from TG breakdown → DHAP → glucose (minor pathway, not significant)", sNote))
story.append(sp(6))
story.append(hr())

# EQ2
story.append(QuestionBox("EQ2",
    "Defective beta-oxidation leads to hypoglycemia.",
    "[2–3 marks]", "WBUHS 2015–2020"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))
story.append(p("• During fasting, the body depends on <b>beta-oxidation</b> to generate ATP for gluconeogenesis", sPoint))
story.append(p("• Beta-oxidation → Acetyl CoA → allosterically activates <b>Pyruvate Carboxylase</b> (1st step of gluconeogenesis)", sPoint))
story.append(p("• Beta-oxidation → NADH + ATP → provide energy needed to drive gluconeogenesis", sPoint))
story.append(p("• If beta-oxidation is defective (e.g., <b>MCAD deficiency</b> — medium-chain acyl CoA dehydrogenase):", sPoint))
story.append(p("  – No Acetyl CoA generated → Pyruvate Carboxylase not activated → gluconeogenesis fails", sPoint))
story.append(p("  – No ATP generated from fats → glucose consumed rapidly → <b>hypoglycemia</b>", sPoint))
story.append(p("  – Normally fats spare glucose by being the primary fuel during fasting", sPoint))
story.append(p("• <b>Clinical:</b> MCAD deficiency — hypoglycemic crisis in infants after overnight fast; no ketonemia (can't produce ketones either)", sNote))
story.append(sp(6))
story.append(hr())

# EQ3 bonus
story.append(QuestionBox("EQ3",
    "Explain why liver cannot use ketone bodies.",
    "[2 marks]", "Commonly asked indirect question"))
story.append(sp(4))
story.append(AnswerSection())
story.append(sp(4))
story.append(p("• Ketone body utilization (ketolysis) requires <b>Succinyl CoA Transferase (Thiophorase)</b> to activate acetoacetate to acetoacetyl CoA", sPoint))
story.append(p("• <b>Liver lacks succinyl CoA transferase</b> — this is a physiological adaptation", sPoint))
story.append(p("• This ensures liver continues to export ketone bodies to brain/muscle during starvation rather than using them itself", sPoint))
story.append(p("• During starvation, ketone bodies become the <b>primary fuel for brain</b> (replaces glucose after 3–4 days fast)", sPoint))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION D: BETA-OXIDATION FLOWCHART (full page)
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION D — FLOWCHART: Beta-Oxidation of Palmitic Acid",
                            sub="Complete pathway with ATP yield table",
                            fill=C_BLUE))
story.append(sp(8))
story.append(BetaOxFlowchart(width=W - 80))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION E: CHOLESTEROL SYNTHESIS FLOWCHART
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION E — FLOWCHART: Cholesterol Synthesis (de novo)",
                            sub="Acetyl CoA → Mevalonate → Squalene → Cholesterol  |  Regulation & clinical notes",
                            fill=C_GREEN))
story.append(sp(8))
story.append(CholSynthFlowchart(width=W - 80))
story.append(PageBreak())

# ════════════════════════════════════════════════════════════════
#  SECTION F: HIGH-YIELD SUMMARY
# ════════════════════════════════════════════════════════════════
story.append(SectionHeader("SECTION F — HIGH-YIELD SUMMARY & EXAM TIPS",
                            sub="Last-minute revision: key facts, comparisons, and disorders",
                            fill=C_AMBER))
story.append(sp(8))

# Comparison Beta-ox vs FA Synthesis
story.append(p("<b>Beta-Oxidation vs Fatty Acid Synthesis — Key Differences (Frequently Asked)</b>", sSubHdr))
story.append(make_table(
    ["Feature", "β-Oxidation", "FA Synthesis"],
    [
        ["Location", "Mitochondrial matrix", "Cytosol"],
        ["Carrier", "CoA", "ACP (Acyl Carrier Protein)"],
        ["Coenzymes", "FAD, NAD⁺ (oxidized)", "NADPH (reduced)"],
        ["CO₂ / HCO₃⁻", "Not used", "HCO₃⁻ required (Malonyl CoA)"],
        ["Rate-limiting enzyme", "CPT-I (transport step)", "Acetyl CoA Carboxylase (ACC)"],
        ["Main product", "Acetyl CoA + FADH₂ + NADH", "Palmitate (C16:0)"],
        ["Activated by", "Glucagon, Epinephrine, Low insulin", "Insulin, Citrate"],
        ["Inhibited by", "Malonyl CoA (via CPT-I)", "Palmitoyl CoA, Glucagon, AMPK"],
        ["Stereospecificity", "L-3-hydroxyacyl CoA intermediate", "D-3-hydroxyacyl-ACP intermediate"],
    ],
    [130, 170, 140],
    hdr_fill=C_DARK_BLUE
))
story.append(sp(8))

# Disorders table
story.append(p("<b>Clinical Disorders of Lipid Metabolism (High-Yield)</b>", sSubHdr))
story.append(make_table(
    ["Disorder", "Defect", "Key Features"],
    [
        ["MCAD Deficiency", "Medium-chain Acyl CoA Dehydrogenase", "Hypoglycemia, no ketonemia, fasting intolerance; SIDS risk"],
        ["Refsum Disease", "Phytanoyl CoA α-Hydroxylase (peroxisomal)", "Phytanic acid accumulation; peripheral neuropathy, retinitis"],
        ["Zellweger Syndrome", "Peroxisome biogenesis (PEX genes)", "VLCFA accumulation; severe neurological defects; fatal early"],
        ["X-linked ALD", "VLCFA transporter (ABCD1) in peroxisomal membrane", "VLCFA accumulation; adrenal insufficiency + CNS demyelination"],
        ["Familial Hypercholesterolemia", "LDL receptor defect (autosomal dominant)", "Very high LDL; xanthomas, xanthelasma; premature MI"],
        ["Tangier Disease", "ABCA1 transporter defect", "Almost no HDL; cholesterol deposits in tonsils (orange tonsils)"],
        ["Gaucher Disease", "Glucocerebrosidase (β-glucosidase)", "Glucocerebroside accumulation in macrophages; hepatosplenomegaly"],
        ["Niemann-Pick Disease", "Sphingomyelinase", "Sphingomyelin accumulation; cherry-red spot; neurodegeneration"],
        ["Tay-Sachs Disease", "Hexosaminidase A", "GM2 ganglioside accumulation; cherry-red spot; fatal by age 4"],
    ],
    [115, 135, 190],
    hdr_fill=C_RED
))
story.append(sp(8))

# Exam tips
story.append(p("<b>⭐ High-Yield Exam Points — Memorise These</b>", sSubHdr))
tips_data = [
    ["1", "Net ATP from palmitic acid = 106 (learn each step of calculation)"],
    ["2", "Oleic acid (C18:1): uses isomerase → 1 FADH₂ less → ~2 ATP less than palmitic"],
    ["3", "CPT-I is rate-limiting for beta-oxidation transport; inhibited by Malonyl CoA"],
    ["4", "ACC (Acetyl CoA Carboxylase) is rate-limiting for FA synthesis; makes Malonyl CoA"],
    ["5", "HMG CoA Reductase is rate-limiting for cholesterol synthesis; target of Statins"],
    ["6", "Statins = competitive inhibitors of HMG CoA Reductase → ↓ LDL cholesterol"],
    ["7", "Carnitine shuttle is required only for long-chain FA (>C12); short/medium chain enter freely"],
    ["8", "Liver CANNOT use ketone bodies (lacks thiophorase); it only makes them"],
    ["9", "Ketone bodies are the preferred fuel of brain during starvation (after 3–4 days)"],
    ["10", "HDL = reverse cholesterol transport = 'good cholesterol'; ApoA-I activates LCAT"],
    ["11", "ApoC-II activates LPL; ApoB-100 is the LDL receptor ligand; ApoE for remnant clearance"],
    ["12", "Choline is the most important lipotropic factor; prevents fatty liver"],
    ["13", "Linoleic acid (18:2, ω-6) → Arachidonic acid → Prostaglandins / Thromboxanes / Leukotrienes"],
    ["14", "LCAT esterifies cholesterol in HDL using phosphatidylcholine as FA donor"],
    ["15", "SREBP pathway: ↓ cholesterol → SREBP activated → ↑ HMG CoA Reductase + LDL receptor"],
    ["16", "Normal cholesterol: <200 mg/dL; LDL <100 mg/dL; HDL >40 (M) or >50 (F) mg/dL; TG <150 mg/dL"],
]
story.append(make_table(
    ["#", "High-Yield Point"],
    tips_data,
    [25, 415],
    hdr_fill=C_AMBER
))

story.append(sp(10))
story.append(SectionHeader(
    "ALL THE BEST FOR YOUR EXAMS! 🎓",
    sub="Prepared from WBUHS PYQ Bank 2010–2023  ·  Lippincott's Biochemistry 8e  ·  Harper's Illustrated Biochemistry",
    fill=C_DARK_BLUE))

# ════════════════════════════════════════════════════════════════
#  BUILD PDF
# ════════════════════════════════════════════════════════════════
PAGE_NUM[0] = 0
doc = SimpleDocTemplate(
    OUTPUT, pagesize=A4,
    topMargin=38, bottomMargin=26,
    leftMargin=40, rightMargin=40,
    title="Lipid Biochemistry Complete PYQ Guide — MBBS 1st Year",
    author="Orris Medical",
)
doc.build(story, onFirstPage=on_page, onLaterPages=on_page)
print(f"PDF saved: {OUTPUT}")