help me with biochemistry and physiology we have to complete it by 2 weeks i already have some idea about everything its gonna be like a revision
Asking for Preferences
Here's how we'll structure your 2-week revision. I'll work with you interactively - covering biochemistry and physiology equally across all major topics for MBBS 1st year, mixing concise notes, high-yield bullets, and Q&A.
2-Week Revision Plan
BIOCHEMISTRY
| Week | Topics |
|---|---|
| Week 1 (Days 1-3) | Carbohydrate metabolism - glycolysis, TCA, glycogen, gluconeogenesis |
| Week 1 (Days 4-5) | Lipid metabolism - fatty acid oxidation, ketone bodies, cholesterol |
| Week 1 (Days 6-7) | Protein & amino acid metabolism - urea cycle, transamination, special AAs |
| Week 2 (Days 1-2) | Molecular biology - DNA replication, transcription, translation, mutations |
| Week 2 (Day 3) | Vitamins, enzymes & integration of metabolism |
PHYSIOLOGY
| Week | Topics |
|---|---|
| Week 1 (Days 1-3) | Cardiovascular - cardiac cycle, ECG, BP regulation, heart sounds |
| Week 1 (Days 4-5) | Respiratory - lung volumes, gas exchange, control of breathing |
| Week 1 (Days 6-7) | Renal - GFR, tubular function, acid-base, concentration |
| Week 2 (Days 1-2) | GI - motility, secretion, digestion & absorption |
| Week 2 (Days 3-4) | Endocrine - pituitary, thyroid, adrenal, pancreas, gonads |
| Week 2 (Day 5) | Nerve & muscle - resting potential, action potential, NMJ |
How This Works
Each session I can give you:
- Concise notes on a topic (key facts, pathways, mechanisms)
- High-yield bullets (what examiners love to ask)
- Q&A drill (questions with explanations)
Just tell me which topic to start with and I'll dive in. For example:
"Start with glycolysis" or "Give me cardiovascular high-yield bullets" or "Quiz me on the urea cycle"
We can go in any order you like - follow the plan above or jump to whatever you're weakest on. What shall we start with?
Start with glycolysis and carbohydrate metabolism
Reading File
Finding Sources
Finding Sources
Reading File
Reading File
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Reading File
I now have everything I need to build a complete, exam-ready glycolysis revision. Here it is:
Glycolysis & Carbohydrate Metabolism - MBBS Revision
PART 1 - Concise Notes
What is Glycolysis?
Glycolysis is the universal 10-step pathway in the cytosol that converts 1 glucose (6C) → 2 pyruvate (3C). It is the hub of carbohydrate metabolism - virtually all dietary sugars (fructose, galactose) are fed into it.
- Aerobic glycolysis: Pyruvate → Acetyl-CoA → TCA cycle (requires O2)
- Anaerobic glycolysis: Pyruvate → Lactate (no O2 needed - used by RBCs, cornea, exercising muscle)
PART 2 - The 10 Steps (Exam Table)
Phase 1 - ENERGY INVESTMENT (Steps 1-5) - costs 2 ATP
| Step | Reaction | Enzyme | Notes |
|---|---|---|---|
| 1 | Glucose → Glucose-6-P | Hexokinase (or Glucokinase in liver) | Irreversible; traps glucose in cell |
| 2 | G-6-P → Fructose-6-P | Phosphoglucose isomerase | Reversible |
| 3 | F-6-P → Fructose-1,6-bisP | Phosphofructokinase-1 (PFK-1) | Rate-limiting step; irreversible |
| 4 | F-1,6-bisP → DHAP + G-3-P | Aldolase | Splits 6C → two 3C |
| 5 | DHAP ⇌ G-3-P | Triose phosphate isomerase | Only G-3-P proceeds |
Phase 2 - ENERGY GENERATION (Steps 6-10) - produces 4 ATP + 2 NADH
| Step | Reaction | Enzyme | Notes |
|---|---|---|---|
| 6 | G-3-P + NAD⁺ → 1,3-bisphosphoglycerate | G-3-P dehydrogenase | Produces NADH; inhibited by arsenic |
| 7 | 1,3-BPG → 3-phosphoglycerate | Phosphoglycerate kinase | 1st substrate-level phosphorylation; makes ATP |
| 8 | 3-PG → 2-PG | Phosphoglycerate mutase | |
| 9 | 2-PG → Phosphoenolpyruvate (PEP) | Enolase | Inhibited by fluoride |
| 10 | PEP → Pyruvate | Pyruvate kinase | 2nd substrate-level phosphorylation; irreversible |
Net yield per glucose: 2 ATP + 2 NADH + 2 Pyruvate
PART 3 - The 3 Regulatory Enzymes (Most Exam-Favourite!)
1. Hexokinase vs Glucokinase
| Feature | Hexokinase (I-III) | Glucokinase (IV) |
|---|---|---|
| Location | All tissues | Liver, pancreatic β-cells |
| Km for glucose | Low (high affinity) | High (low affinity) |
| Inhibited by G-6-P? | Yes (product inhibition) | No |
| Induced by insulin? | No | Yes |
| Function | Works at low glucose | Works only when glucose is high (after meals) |
2. PFK-1 - The Rate-Limiting Enzyme
| Activated by | Inhibited by |
|---|---|
| AMP, ADP | ATP, Citrate |
| Fructose-2,6-bisphosphate (most potent activator) | Glucagon (via lowering F-2,6-bisP) |
| Low pH activates... | ...actually inhibits (protective in ischemia) |
Insulin raises F-2,6-bisP → activates PFK-1 → promotes glycolysis Glucagon lowers F-2,6-bisP → inhibits PFK-1 → promotes gluconeogenesis
3. Pyruvate Kinase
- Activated by: F-1,6-bisP (feedforward activation)
- Inhibited by: ATP, Acetyl-CoA, glucagon (via phosphorylation)
- Deficiency: Hemolytic anemia (RBCs can't maintain ATP for Na/K pump)
PART 4 - ATP Yield Summary
| Condition | ATP per glucose |
|---|---|
| Anaerobic glycolysis | 2 ATP |
| Aerobic glycolysis (full oxidation) | ~30-32 ATP (older textbooks say 36-38) |
- Steps 1 & 3 consume 1 ATP each = 2 ATP used
- Steps 7 & 10 produce 1 ATP each × 2 (two 3C units) = 4 ATP made
- Net = 2 ATP (substrate-level phosphorylation)
PART 5 - Glucose Transporters (GLUTs) - High Yield!
| GLUT | Location | Special Feature |
|---|---|---|
| GLUT-1 | RBCs, brain, most tissues | Basal uptake; always present |
| GLUT-2 | Liver, kidney, pancreatic β-cells, small intestine | High Km - glucose sensor |
| GLUT-3 | Brain (neurons) | High affinity - brain gets glucose first |
| GLUT-4 | Muscle, adipose | Insulin-stimulated - most clinically important |
| GLUT-5 | Small intestine | Transports fructose |
PART 6 - Fates of Pyruvate
┌─→ Acetyl-CoA (aerobic) → TCA cycle
Glucose → Pyruvate ─┤
├─→ Lactate (anaerobic)
├─→ Alanine (transamination)
├─→ Oxaloacetate (gluconeogenesis via pyruvate carboxylase)
└─→ Ethanol (yeast/microorganisms)
PART 7 - High-Yield Bullet Points
- Fluoride inhibits enolase (step 9) - used in blood collection tubes to prevent glycolysis
- Arsenic inhibits G-3-P dehydrogenase (step 6) - uncouples substrate-level phosphorylation
- RBCs have no mitochondria - depend entirely on anaerobic glycolysis
- 2,3-BPG (made from 1,3-BPG via Luebering-Rapoport shunt) decreases Hb O2 affinity - important in RBCs
- Pasteur effect: O2 inhibits anaerobic glycolysis (O2 presence → less lactate production)
- Warburg effect: Cancer cells prefer glycolysis even in presence of O2 (aerobic glycolysis)
- Lactic acidosis: occurs when pyruvate → lactate accumulates (shock, thiamine deficiency, metformin OD)
PART 8 - Quick Q&A Drill
Q1. Which enzyme is the main regulatory/rate-limiting enzyme of glycolysis?
PFK-1 (phosphofructokinase-1)
Q2. Why can RBCs only do anaerobic glycolysis?
No mitochondria - cannot do oxidative phosphorylation or TCA
Q3. What is the most potent activator of PFK-1?
Fructose-2,6-bisphosphate (produced by PFK-2, activated by insulin)
Q4. Glucokinase vs Hexokinase - which works after a big carbohydrate meal?
Glucokinase - it has high Km so only fires when glucose is high
Q5. What happens to NADH produced in glycolysis if there is no O2?
It is reoxidized to NAD⁺ when pyruvate is reduced to lactate by lactate dehydrogenase (LDH) - this regenerates NAD⁺ to keep glycolysis running
Q6. Name the 3 irreversible steps of glycolysis.
Steps 1, 3, 10 - catalyzed by Hexokinase, PFK-1, Pyruvate kinase
Q7. A patient with pyruvate kinase deficiency presents with hemolytic anemia. Why?
RBCs need ATP from PK for the Na⁺/K⁺-ATPase pump to maintain cell shape. Without PK, ATP falls → cell swells → hemolysis
Sources: Lippincott Illustrated Reviews: Biochemistry 8e | Harper's Illustrated Biochemistry 32e | Basic Medical Biochemistry: A Clinical Approach 6e
What next? We can:
- Go deeper into the TCA cycle (follows glycolysis directly)
- Move to glycogen metabolism (glycogenesis + glycogenolysis)
- Do gluconeogenesis (the reverse pathway - bypasses the 3 irreversible steps)
- Quiz you more on glycolysis before moving on
What would you like?
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