Biochemistry Foundations

🏥 Biochemistry Foundations

Part 1 of 7 — Amino Acids & Protein Structure

20 standard amino acids: nonpolar (G,A,V,L,I,P,F,W,M), polar (S,T,C,Y,N,Q), charged (D,E,K,R,H).

Protein structure: primary (sequence), secondary (alpha-helix, beta-sheet), tertiary (3D fold), quaternary (subunits).

Concept Check 🎯

Key Insight: Peptide bond: planar, partial double-bond character, trans configuration preferred.

MCAT Tip: pI = isoelectric point — pH where net charge = 0; average of flanking pKa values.

Concept Check 🎯

Fill in the Blanks 🔍

Enzyme Kinetics

Part 2 of 7 — Enzyme Kinetics

Michaelis-Menten: v = Vmax[S]/(Km+[S]); Km = substrate concentration at half-Vmax.

Lineweaver-Burk plot: 1/v vs 1/[S] — y-intercept = 1/Vmax, x-intercept = -1/Km.

Concept Check 🎯

Key Insight: Competitive inhibitor: binds active site, increases apparent Km, Vmax unchanged.

MCAT Tip: Non-competitive inhibitor: binds allosteric site, decreases Vmax, Km unchanged.

Concept Check 🎯

Fill in the Blanks 🔍

Carbohydrate Metabolism

Part 3 of 7 — Carbohydrate Metabolism

Glycolysis: glucose to 2 pyruvate, net 2 ATP + 2 NADH (cytoplasm, anaerobic).

Pyruvate dehydrogenase: pyruvate to acetyl-CoA + CO2 + NADH (mitochondrial matrix).

Concept Check 🎯

Key Insight: Citric acid cycle (Krebs): acetyl-CoA to 2 CO2 + 3 NADH + 1 FADH2 + 1 GTP per turn.

MCAT Tip: Gluconeogenesis: essentially reverse glycolysis with 4 bypass enzymes — occurs in liver.

Concept Check 🎯

Fill in the Blanks 🔍

Lipids & Membranes

Part 4 of 7 — Lipids & Membranes

Fatty acids: saturated (no double bonds, straight) vs unsaturated (double bonds, kinked).

Beta-oxidation: fatty acid to acetyl-CoA units, producing FADH2 and NADH per cycle.

Concept Check 🎯

Key Insight: Cell membrane: phospholipid bilayer with cholesterol for fluidity and integral/peripheral proteins.

MCAT Tip: Lipid-soluble signals (steroids) cross the membrane; water-soluble signals need receptors.

Concept Check 🎯

Fill in the Blanks 🔍

Nucleic Acids & DNA

Part 5 of 7 — Nucleic Acids & DNA

DNA: deoxyribose sugar, A-T (2 H-bonds), G-C (3 H-bonds), antiparallel double helix.

Replication: semiconservative, 5-to-3 direction, DNA polymerase III, leading/lagging strands.

Concept Check 🎯

Key Insight: Transcription: DNA to mRNA by RNA polymerase; processing includes 5-cap, poly-A tail, splicing.

MCAT Tip: Translation: mRNA to protein at ribosome; tRNA brings amino acids; codons read 5-to-3.

Concept Check 🎯

Fill in the Blanks 🔍

Bioenergetics & ATP

Part 6 of 7 — Bioenergetics & ATP

Oxidative phosphorylation: ETC creates proton gradient; ATP synthase uses it to make ATP.

NADH yields ~2.5 ATP; FADH2 yields ~1.5 ATP (via Complex I and II respectively).

Concept Check 🎯

Key Insight: Complete glucose oxidation: ~30-32 ATP total (glycolysis + Krebs + ETC).

MCAT Tip: Chemiosmotic theory (Peter Mitchell): proton motive force drives ATP synthesis across inner mitochondrial membrane.

Concept Check 🎯

Fill in the Blanks 🔍

Review & MCAT Practice

Part 7 of 7 — Review & MCAT Practice

Oxidative phosphorylation: ETC creates proton gradient; ATP synthase uses it to make ATP.

NADH yields ~2.5 ATP; FADH2 yields ~1.5 ATP (via Complex I and II respectively).

Concept Check 🎯

Key Insight: Complete glucose oxidation: ~30-32 ATP total (glycolysis + Krebs + ETC).

MCAT Tip: Chemiosmotic theory (Peter Mitchell): proton motive force drives ATP synthesis across inner mitochondrial membrane.

Concept Check 🎯

Fill in the Blanks 🔍