MCB 102

How to Use This for Time-Efficient Review

Restructured from Lehninger's chapter order into MCB 102's actual course structure: three ~5-week modules, each capped by its own non-cumulative exam. Built for efficient review, not cover-to-cover reading. For each module, skim the high-yield checklist first — if you can already explain every item, spend remaining time on problem sets rather than re-reading. Only drop into the concept notes for items you can't yet explain out loud without notes.

Molecular Foundations — Water, Amino Acids, Protein Structure/Function, Enzymes

High-Yield Checklist

• Calculate pH/pKa problems using Henderson–Hasselbalch; explain how a buffer resists pH change
• Classify all 20 amino acids by side chain (nonpolar, polar, acidic, basic, aromatic) and predict pI
• Explain why the peptide bond is planar and mostly trans
• Describe α-helix and β-sheet stabilization (backbone H-bonds) and read a Ramachandran plot
• State Anfinsen's conclusion (sequence determines fold) and what chaperones actually do (prevent misfolding, don't dictate structure)
• Explain hyperbolic (myoglobin) vs. sigmoidal (hemoglobin) O₂-binding curves; define cooperativity, the Bohr effect, and 2,3-BPG's role
• Derive/interpret Michaelis–Menten kinetics: Km, Vmax, what each represents physically
• Distinguish competitive, noncompetitive, and uncompetitive inhibition on a Lineweaver–Burk plot
• List enzyme catalytic strategies (acid-base catalysis, covalent catalysis, metal ion catalysis, transition-state stabilization)

Concept Notes

Water & Acid-Base. The hydrophobic effect is entropy-driven — ordering water around nonpolar solutes costs entropy, so nonpolar groups cluster to minimize that cost. Buffers work best within ±1 pH unit of their pKa. This topic is foundational but usually tested in combination with amino acid ionization, not alone.

Amino Acids → Proteins. Primary structure = sequence. Secondary structure = local backbone H-bonding patterns (helix/sheet). Tertiary = full 3D fold, driven mainly by burying hydrophobic residues in the core. Quaternary = multi-subunit assembly (hemoglobin is the classic example).

Protein Function. One of the most reliably tested topics in Module 1. Myoglobin's curve is hyperbolic (single O₂ binding site, no cooperativity); hemoglobin's is sigmoidal (4 subunits, cooperative binding, T-state ↔ R-state transition). The Bohr effect (lower pH → lower O₂ affinity) explains why hemoglobin releases O₂ more readily in metabolically active, CO₂-rich, acidic tissue.

Bioenergetics and Metabolism

High-Yield Checklist

• Explain ΔG vs. ΔG°′ — why cellular reactions run on actual concentrations, not standard state
• Explain why ATP is thermodynamically favorable to hydrolyze (resonance stabilization, charge repulsion relief, hydration)
• List glycolysis's 3 irreversible/regulated steps (hexokinase, PFK-1, pyruvate kinase) and their gluconeogenic bypass enzymes
• Explain reciprocal regulation between glycolysis and gluconeogenesis via fructose-2,6-bisphosphate
• State net ATP/NADH yield of glycolysis (2 ATP, 2 NADH per glucose)
• Explain pyruvate dehydrogenase as the irreversible link between glycolysis and the TCA cycle
• List TCA cycle inputs/outputs per turn (3 NADH, 1 FADH₂, 1 GTP/ATP, 2 CO₂) and the 2 major regulated enzymes
• Explain chemiosmosis: how ETC proton pumping creates a gradient that ATP synthase converts into ATP
• Know the approximate ATP yield per NADH (~2.5) vs. per FADH₂ (~1.5) and why they differ
• Explain what an uncoupler (e.g., DNP, UCP1/thermogenin) does to the proton gradient and ATP yield
• Walk through β-oxidation logic and calculate ATP yield from a given fatty acid chain length

Concept Notes

Bioenergetics Basics. The most commonly missed conceptual point: ΔG°′ describes standard conditions; ΔG describes what actually happens in the cell given real substrate/product concentrations. A reaction with unfavorable ΔG°′ can still run forward in vivo if the product is rapidly consumed, keeping the reaction pulled forward.

Glycolysis/Gluconeogenesis. Gluconeogenesis is not glycolysis in reverse — three glycolytic steps are irreversible in the cell and must be bypassed by distinct enzymes. This reciprocal on/off relationship is one of the most exam-tested regulatory relationships in the course, often via a "what happens to X if insulin/glucagon is elevated" question.

Oxidative Phosphorylation. The conceptual centerpiece of Module 2: electron flow through Complexes I–IV pumps protons into the intermembrane space, creating a proton-motive force; ATP synthase uses the energy of protons flowing back down that gradient to drive rotational catalysis and phosphorylate ADP.

Fatty Acid Oxidation. Numeric ATP-yield calculation problems are common — an n-carbon fatty acid undergoes (n/2 − 1) rounds of β-oxidation, each producing one FADH₂, one NADH, and one acetyl-CoA.

Molecular Biology — DNA, RNA, Protein Synthesis, Gene Regulation

High-Yield Checklist

• Explain semiconservative DNA replication (Meselson–Stahl logic)
• Describe replication fork machinery: helicase, primase, DNA polymerase, and why leading/lagging strands are synthesized differently
• Explain Okazaki fragments and the role of DNA ligase
• Explain proofreading (3'→5' exonuclease) and mismatch repair
• Describe transcription: promoter recognition, elongation, termination; know eukaryotic RNA processing (5' cap, poly-A tail, splicing)
• Explain why mature mRNA is shorter than the primary transcript (intron removal) and what alternative splicing accomplishes
• Describe translation stages: initiation (start codon), elongation (aminoacyl-tRNA delivery), termination (stop codon, release factors)
• Explain wobble at the third codon position and why it reduces the impact of point mutations
• Walk through the lac operon: repressor-bound = OFF; allolactose binding = de-repression; CAP-cAMP binding = needed for strong "ON" when glucose is low
• Distinguish transcriptional vs. post-transcriptional vs. post-translational regulation, with an example of each

Concept Notes

Transcription & RNA Processing. Splicing removes introns and joins exons — a common point of confusion is why mature mRNA is significantly shorter than the DNA region it was transcribed from. Alternative splicing (different exon combinations) is how one gene can produce multiple protein isoforms — a frequent short-answer topic.

Translation. The genetic code is triplet, degenerate, and (near-)universal. Wobble pairing at the third codon position is why fewer than 61 tRNAs suffice for the 61 sense codons — tested mainly to explain why third-position point mutations are often "silent" (synonymous).

Fast Cross-Module Connections

Worth 5 minutes of review before any exam.

Time-Efficient Study Strategy

1. Do the checklist self-test first, for whichever module's exam is coming up. Anything you can't explain out loud in 30 seconds — that's where your remaining study time goes.
2. Prioritize mechanism-heavy topics (enzyme kinetics, chemiosmosis, DNA replication fork logic, lac operon) over memorization-heavy topics (full pathway diagrams) — exams tend to reward reasoning through a perturbation over reciting every intermediate.
3. Skip chapter-numbering precision. You need to explain the concept and apply it to a novel scenario, not know which exact Lehninger section it's in.
4. If you get syllabus access, grab just the lecture topic list and exam dates — that alone pins down exactly which module you're in and what to prioritize this week.

This guide prioritizes exam-relevant conceptual mastery over exhaustive coverage. Pair it with a handful of practice problems per module — application-style practice is the highest-leverage use of remaining study time for this kind of course.