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Final Exam Notes - Medical Chemistry
Chapter 1. Fundamental Concepts of Medical Chemistry
1.1 Atomic & Molecular Structure
| Term | Definition |
|---|---|
| Atomic number (Z) | Number of protons (defines the element) |
| Mass number (A) | Protons + neutrons |
| Isotopes | Same element, different neutron count (e.g., C-12 vs C-14) |
| Mole | 6.022 × 10²³ particles (Avogadro's number) |
| Molar mass | Mass of 1 mole in grams (= atomic/molecular weight in g/mol) |
- Molecular formula = actual number of atoms (e.g., C₆H₁₂O₆)
- Empirical formula = simplest ratio (e.g., CH₂O)
1.2 Chemical Bonding & Intermolecular Forces
| Bond Type | How It Forms | Example |
|---|---|---|
| Ionic | Metal donates electrons to nonmetal | NaCl |
| Covalent | Two nonmetals share electrons | H₂O |
| Polar covalent | Unequal sharing → dipole moment | H₂O, HCl |
- Hydrogen bonding: between H and (N, O, or F). Holds DNA double helix together; maintains protein secondary structure.
- Van der Waals forces: weak, short-range attractions. Important in lipid bilayer stability.
1.3 Chemical Reactions
| Reaction Type | Definition | Bio Example |
|---|---|---|
| Oxidation-Reduction (Redox) | Transfer of electrons | Glucose oxidation; NAD⁺→NADH |
| Substitution | One atom/group replaced by another | Drug metabolism |
| Condensation | Two molecules join, releasing H₂O | Peptide bond formation |
| Hydrolysis | Bond broken by adding H₂O | Digestion of proteins/lipids |
| Neutralization | Acid + Base → Salt + H₂O | Antacids neutralizing gastric acid |
- NAD⁺/NADH system: NAD⁺ is the oxidized form (electron acceptor); NADH is reduced (carries electrons to electron transport chain).
1.4 Acids, Bases, and pH
Three Definitions:
| Concept | Acid | Base |
|---|---|---|
| Arrhenius | Releases H⁺ | Releases OH⁻ |
| Bronsted-Lowry | Proton donor | Proton acceptor |
| Lewis | Electron pair acceptor | Electron pair donor |
Key equations:
- pH = -log[H⁺]
- pOH = -log[OH⁻]
- pH + pOH = 14 (at 25°C)
- Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA])
- Used to calculate buffer pH and determine ratio of conjugate base to acid
Strong vs. Weak:
- Strong acids (HCl, H₂SO₄): fully dissociate, Ka is very large
- Weak acids (acetic acid, carbonic acid): partially dissociate; Ka and pKa describe strength
Medical relevance:
| Condition | Blood pH | Cause |
|---|---|---|
| Normal | 7.35-7.45 | - |
| Acidosis | < 7.35 | CO₂ retention, lactic acid |
| Alkalosis | > 7.45 | Hyperventilation, vomiting |
| Gastric acid | ~2 | HCl secretion |
Chapter 2. Alcohols, Ethers, and Carbonyl Compounds
2.1 Alcohols
- General formula: CₙH₂ₙ₊₁OH
- Classification by carbon attached to -OH:
- 1° (primary): -CH₂OH
- 2° (secondary): -CHOH
- 3° (tertiary): -COH
- Properties: H-bonding → higher boiling point + water solubility
- Oxidation reactions:
- 1° alcohol → Aldehyde → Carboxylic acid
- 2° alcohol → Ketone
- 3° alcohol → No oxidation (no H on carbon)
Medical examples:
- Ethanol: antiseptic (denatures proteins)
- Methanol: toxic (metabolized to formaldehyde → blindness, death)
- Glycerol: humectant in pharmaceuticals
2.2 Ethers
- Structure: R-O-R' (two organic groups linked by oxygen)
- Isomerism: functional group isomers of alcohols (same formula, different group)
- Properties: relatively non-polar, low boiling point
- Pharmaceutical use: diethyl ether was used as an anesthetic
2.3 Aldehydes & Ketones
- Carbonyl group (C=O): electrophilic carbon → reactive with nucleophiles
- Aldehydes (R-CHO) vs. Ketones (R-CO-R')
Identification tests:
| Test | Reagent | Positive Result | Detects |
|---|---|---|---|
| Tollens' | [Ag(NH₃)₂]⁺ | Silver mirror | Aldehydes only |
| Fehling's | Cu²⁺ (blue) | Red/orange Cu₂O precipitate | Aldehydes only |
Examples:
- Formaldehyde (HCHO): preservative (formalin)
- Acetone (CH₃COCH₃): solvent; found in urine/breath in diabetic ketoacidosis
Chapter 3. Carbohydrates
3.1 Classification
| Class | Examples | Details |
|---|---|---|
| Monosaccharides | Glucose, fructose, galactose | Single sugar unit |
| Disaccharides | Sucrose, lactose, maltose | Two sugar units |
| Polysaccharides | Glycogen, starch, cellulose, chitin | Many sugar units |
3.2 Structural Aspects
- Aldose: aldehyde functional group (e.g., glucose)
- Ketose: ketone functional group (e.g., fructose)
- Glycosidic bonds:
- α-1,4: in starch and glycogen (digestible)
- β-1,4: in cellulose (not digestible by humans)
- Stereoisomerism:
- D-form (natural biological sugars) vs. L-form
- Epimers: differ at one carbon (e.g., glucose vs. galactose differ at C-4)
3.3 Clinical Importance
- Primary energy source → glycolysis → ATP
- Glycogen: stored in liver (blood glucose regulation) and muscle (local energy)
- Benedict's test: reduces Cu²⁺ → brick-red Cu₂O precipitate; detects reducing sugars (glucose, maltose, lactose - NOT sucrose)
- Diabetes: monitored by blood glucose and HbA1c
Chapter 4. Lipids
4.1 Classification
| Type | Examples |
|---|---|
| Simple lipids | Triglycerides (glycerol + 3 fatty acids) |
| Complex lipids | Phospholipids, glycolipids, sphingolipids |
| Derived lipids | Steroids, fat-soluble vitamins (A, D, E, K) |
4.2 Fatty Acids
- Saturated: no double bonds, solid at room temperature (e.g., palmitic acid)
- Unsaturated: 1+ double bonds, liquid at room temperature
- Monounsaturated (1 double bond): oleic acid
- Polyunsaturated (2+ double bonds): linoleic, arachidonic
- Essential fatty acids (cannot be synthesized; must be consumed):
- Linoleic acid (omega-6)
- Linolenic acid (omega-3)
- Arachidonic acid (omega-6)
- Omega-3: anti-inflammatory, cardioprotective
- Omega-6: pro-inflammatory in excess
4.3 Biological Functions
- Energy storage (9 kcal/g vs. 4 kcal/g for carbs/protein)
- Cell membrane components (phospholipid bilayer)
- Hormone precursors (steroid hormones from cholesterol)
- Lipoproteins:
- HDL ("good"): transports cholesterol to liver for excretion
- LDL ("bad"): deposits cholesterol in artery walls → atherosclerosis
- Statins: inhibit HMG-CoA reductase → lower LDL
- High triglycerides = cardiovascular risk factor
Chapter 5. Amines and Alkaloids
5.1 Structure and Basicity
- Derived from NH₃ by replacing H with organic groups
- Classification:
- Primary (1°): one R group (-NH₂)
- Secondary (2°): two R groups (-NHR)
- Tertiary (3°): three R groups (-NR₂)
- Quaternary (4°): four R groups, permanent positive charge (-NR₄⁺)
- Weak bases: accept protons → form water-soluble salts with acids
- pKa determines how much is protonated at physiological pH (7.4)
5.2 Biological Amines (Neurotransmitters)
| Amine | Role |
|---|---|
| Dopamine | Reward, motor control (deficiency → Parkinson's) |
| Serotonin | Mood, sleep (low levels → depression) |
| Epinephrine (adrenaline) | Fight-or-flight, raises heart rate |
| Acetylcholine | Nerve-muscle junction, memory |
| Histamine | Allergic response, gastric acid secretion |
Drugs acting on amines:
- SSRIs (e.g., fluoxetine/Prozac): block serotonin reuptake → treat depression
- Antihistamines: block histamine receptors → treat allergies
- Amphetamines: stimulants, increase dopamine/norepinephrine release
5.3 Alkaloids
Naturally occurring, nitrogen-containing plant-derived bases:
| Alkaloid | Source | Use/Effect |
|---|---|---|
| Morphine | Poppy | Pain relief (opioid) |
| Quinine | Cinchona bark | Antimalarial |
| Nicotine | Tobacco | Stimulant (addictive) |
| Caffeine | Coffee/tea | CNS stimulant |
| LSD | Ergot fungus | Hallucinogen |
Chapter 6. Amides and Peptides
6.1 Amide Bond Chemistry
- Formed by: Carboxylic acid + Amine → Amide + H₂O (condensation)
- Features: resonance stabilization gives partial double-bond character → rigid, planar structure
- This rigidity is key in protein backbone geometry
6.2 Protein Structure
| Level | Description | Stabilized by |
|---|---|---|
| Primary | Amino acid sequence | Peptide (covalent) bonds |
| Secondary | α-helix, β-sheet | Hydrogen bonds |
| Tertiary | 3D folding of whole chain | H-bonds, disulfide bonds, hydrophobic, ionic |
| Quaternary | Multiple subunits | Same as tertiary |
- Denaturation: disruption of 3D structure by heat, pH change, or detergents (does NOT break peptide bonds, only non-covalent forces)
6.3 Biomedical Examples
| Protein/Peptide | Function |
|---|---|
| Insulin | Peptide hormone, lowers blood glucose |
| Collagen | Structural protein (skin, bone, cartilage) |
| Glutathione | Antioxidant tripeptide (Glu-Cys-Gly) |
| Angiotensin | Blood pressure regulation |
Amide-containing drugs:
- Lidocaine: amide-type local anesthetic
- Penicillin: β-lactam (cyclic amide) antibiotic
Chapter 7. Enzymes in Diagnostics and Therapy
7.1 Structure & Function
- Mostly proteins; some are RNA (ribozymes)
- Catalysts: speed up reactions without being consumed
- Active site: specific region where substrate binds
- Lock-and-key model: rigid fit between enzyme and substrate
- Induced-fit model: enzyme changes shape upon substrate binding (more accurate)
- Factors affecting activity: temperature, pH, inhibitors, cofactors
7.2 Kinetics and Inhibition
- Km (Michaelis constant): substrate concentration at half-Vmax; lower Km = higher affinity
- Vmax: maximum reaction rate (when all enzyme active sites are saturated)
| Inhibitor Type | Mechanism | Effect on Km | Effect on Vmax | Example |
|---|---|---|---|---|
| Competitive | Mimics substrate, blocks active site | Increases | No change | Methotrexate (vs. DHFR) |
| Noncompetitive | Binds allosteric site | No change | Decreases | Heavy metals |
| Irreversible | Covalent bond with enzyme | - | Decreases permanently | Aspirin (COX), nerve agents |
7.3 Diagnostic & Therapeutic Use
Diagnostic enzymes (elevated levels = disease):
| Enzyme | Disease Indicated |
|---|---|
| Amylase / Lipase | Pancreatitis |
| CK-MB (creatine kinase) | Myocardial infarction (heart attack) |
| ALT / AST | Liver disease (hepatitis, cirrhosis) |
| LDH | Multiple (tissue damage) |
Therapeutic enzymes:
- Streptokinase / tPA: dissolve blood clots (fibrinolysis)
- Enzyme replacement therapy: Gaucher's disease (β-glucocerebrosidase deficiency)
Chapter 8. Steroids and Hormones
8.1 Core Structure
- Cyclopentanoperhydrophenanthrene nucleus: 3 cyclohexane rings + 1 cyclopentane ring fused together
- All steroids are derived from cholesterol
8.2 Hormonal Classes
| Steroid Class | Examples | Function |
|---|---|---|
| Corticosteroids | Cortisol | Stress response, anti-inflammation |
| Mineralocorticoids | Aldosterone | Renal Na⁺ retention → blood pressure control |
| Sex hormones (androgens) | Testosterone | Male secondary sexual characteristics |
| Sex hormones (estrogens) | Estrogen | Female characteristics, menstrual cycle |
| Progestins | Progesterone | Maintains pregnancy |
| Vitamin D | Calcitriol | Calcium absorption (gut), bone mineralization |
- Anabolic steroids: synthetic androgens; abuse causes liver damage, hormonal suppression, cardiovascular disease
- Steroids are lipid-soluble → cross plasma membrane → bind intracellular receptors → act on DNA directly
8.3 Medical Applications
- Prednisone (corticosteroid): treats asthma, autoimmune diseases, inflammation
- Hormone replacement therapy (HRT): menopause, hypogonadism
- Lipid solubility → long-acting, oral or injectable dosing
Chapter 9. Vitamins and Coenzymes
9.1 Classification
| Group | Vitamins | Storage | Risk |
|---|---|---|---|
| Fat-soluble | A, D, E, K | Liver/adipose | Toxicity with excess |
| Water-soluble | C, B-complex | Minimal | Deficiency if not replenished daily |
9.2 Functions and Deficiencies - Quick Reference Table
| Vitamin | Function | Deficiency Disease |
|---|---|---|
| A (Retinol) | Vision (rhodopsin), epithelial integrity | Night blindness, xerophthalmia |
| D (Calciferol) | Calcium absorption, bone mineralization | Rickets (children), Osteomalacia (adults) |
| E (Tocopherol) | Antioxidant, protects cell membranes | Neurological disorders, hemolytic anemia |
| K | Clotting factors II, VII, IX, X synthesis | Bleeding tendency (coagulopathy) |
| C (Ascorbic acid) | Collagen synthesis, antioxidant, iron absorption | Scurvy (bleeding gums, poor wound healing) |
| B1 (Thiamine) | Nerve function, pyruvate dehydrogenase | Beriberi, Wernicke-Korsakoff |
| B3 (Niacin) | NAD⁺ synthesis, energy metabolism | Pellagra (dermatitis, diarrhea, dementia) |
| B12 (Cobalamin) | RBC formation, myelin synthesis, DNA | Pernicious anemia, subacute combined degeneration |
9.3 Coenzyme Functions
| Coenzyme | Derived from | Role |
|---|---|---|
| NAD⁺/NADH | Niacin (B3) | Electron carrier in oxidation reactions |
| FAD/FADH₂ | Riboflavin (B2) | Electron carrier (Krebs cycle) |
| CoA (Coenzyme A) | Pantothenic acid (B5) | Carries acyl groups (acetyl-CoA in Krebs cycle) |
| Biotin | Biotin (B7) | CO₂ carrier in carboxylation reactions |
Chapter 10. Acids, Bases, and Buffers in Medicine
10.1 Concepts (Recap)
- pH = -log[H⁺]; physiological range = 7.35-7.45
- pKa: lower pKa = stronger acid
- A buffer works best when pH ≈ pKa (within ±1 pH unit)
10.2 Buffer Systems
| Buffer System | Equation | Location/Role |
|---|---|---|
| Bicarbonate | CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻ | Blood; regulated by lungs (CO₂) and kidneys (HCO₃⁻) |
| Phosphate | H₂PO₄⁻ ⇌ H⁺ + HPO₄²⁻ | Intracellular fluid; renal tubules |
| Protein | Hemoglobin, plasma proteins | Blood (hemoglobin in RBCs) |
- Antacids (e.g., sodium bicarbonate, Mg(OH)₂): neutralize excess gastric HCl
10.3 Acid-Base Disorders
| Disorder | pH | Primary Change | Cause |
|---|---|---|---|
| Respiratory acidosis | < 7.35 | ↑ CO₂ | Hypoventilation, COPD |
| Respiratory alkalosis | > 7.45 | ↓ CO₂ | Hyperventilation, anxiety |
| Metabolic acidosis | < 7.35 | ↓ HCO₃⁻ | Lactic acidosis, DKA, diarrhea |
| Metabolic alkalosis | > 7.45 | ↑ HCO₃⁻ | Vomiting (loss of HCl), excess antacids |
Chapter 11. Radioactivity in Medicine
11.1 Principles of Nuclear Chemistry
| Radiation | Symbol | Nature | Penetration |
|---|---|---|---|
| Alpha (α) | ⁴₂He | Helium nucleus | Low (stopped by paper/skin) |
| Beta (β) | e⁻ | Electron | Medium (stopped by plastic/glass) |
| Gamma (γ) | γ | High-energy photon | High (requires lead/concrete) |
- Half-life (t½): time for 50% of radioactive atoms to decay
- Units:
- Becquerel (Bq): 1 decay per second (SI unit)
- Curie (Ci): 3.7 × 10¹⁰ disintegrations/second
- Gray (Gy): absorbed dose (1 J/kg)
- Sievert (Sv): biological dose equivalent (Gy × quality factor)
11.2 Medical Applications
| Technique | Isotope | Use |
|---|---|---|
| PET scan | F-18 (Fluorine-18) | Metabolic imaging (cancer, brain activity) |
| SPECT | Tc-99m (Technetium-99m) | Organ perfusion (heart, bone, thyroid) |
| CT | X-rays (not isotope) | Structural/anatomical imaging |
| Thyroid therapy | I-131 (Iodine-131) | Hyperthyroidism, thyroid cancer |
| Tumor therapy | Co-60 (Cobalt-60) | External beam radiotherapy |
| Sterilization | Gamma rays | Sterilize surgical instruments |
11.3 Radiation Safety - ALARA Principle
ALARA = As Low As Reasonably Achievable
Three methods of protection:
- Time: minimize time of exposure
- Distance: maximize distance from source (dose ∝ 1/distance²)
- Shielding: use lead aprons, concrete walls
- Most radiosensitive tissue: bone marrow (rapidly dividing cells)
- Biological effects: DNA strand breaks → mutation, cancer, cell death
Chapter 12. Qualitative Tests for Functional Groups
Master this table - high exam likelihood!
| Test | Reagent | Detects | Positive Observation |
|---|---|---|---|
| Molisch's Test | α-naphthol + H₂SO₄ | All carbohydrates | Purple ring at interface |
| Benedict's Test | Cu²⁺ (alkaline) | Reducing sugars (aldehyde sugars) | Brick-red Cu₂O precipitate |
| Tollens' Test | [Ag(NH₃)₂]⁺ | Aldehydes | Silver mirror |
| Fehling's Test | Cu²⁺ (blue) | Aldehydes | Red Cu₂O precipitate |
| Biuret Test | Cu²⁺ in NaOH | Peptide bonds / proteins | Violet/purple color |
| Ninhydrin Test | Ninhydrin | Free amino acids / amines | Purple-blue (Ruhemann's purple) |
| Diazotization Test | NaNO₂ + HCl | Aromatic primary amines | Colored azo dye |
| Ferric Chloride Test | FeCl₃ | Phenols | Violet/purple color |
| Salkowski Test | H₂SO₄ (conc.) | Steroids / cholesterol | Reddish/violet in chloroform layer |
| Iodoform Test | I₂ + NaOH | Methyl ketones or ethanol | Yellow CHI₃ precipitate |
| Bromine Water / KMnO₄ | Br₂(aq) or KMnO₄ | C=C double bonds (alkenes/unsaturated fats) | Decolorization |
| Jones Oxidation | Chromic acid (CrO₃) | Primary vs. secondary alcohols | Orange → green |
| Lead Acetate Test | Pb(CH₃COO)₂ | Sulfides (H₂S) | Black PbS precipitate |
| Brown Ring Test | Fe²⁺ + H₂SO₄ | Nitrates / nitro compounds | Brown ring at interface |
| Amide Hydrolysis | Acid or base + heat | Amides/peptides | Yields acid + amine products |
| IR Spectroscopy | Infrared light | Functional groups by vibration | C=O peak ~1700 cm⁻¹; O-H ~3400 cm⁻¹ |
Quick Memorization Tips
- pH disorders: "Respiratory = CO₂; Metabolic = HCO₃⁻" - the one that matches the direction of pH change is the primary cause.
- Vitamins: Fat-soluble = "ADEK" (A, D, E, K); deficiencies = "Night, Rickets, Nerve, Bleed"
- Enzymes: "CK-MB = Heart attack; Amylase = Pancreatitis; ALT/AST = Liver"
- Tests: "Tollens = Silver mirror; Benedict = Brick-red; Biuret = Violet"
- Isotopes: "PET = F-18 for metabolic; SPECT = Tc-99m for perfusion; I-131 for thyroid"
- Protein structure: "Please Send Tertiary Quarters" = Primary → Secondary → Tertiary → Quaternary
- Steroid core: 4 fused rings (3 hexagons + 1 pentagon) - all derived from cholesterol
These notes cover all 12 chapters in your review sheet. Every topic, test, clinical correlation, and key formula from the exam guide is included. Good luck on your final!
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