Overview
This lecture covers key MCAT practice questions across biology, chemistry, physics, psychology, and sociology, focusing on fundamental concepts and reasoning behind correct answers.
Enzyme Kinetics and Biochemistry
- Enzymes decrease activation energy, increasing reaction rates, but do not change delta G (free energy change).
- Most human enzymes have optimal activity at 37°C and pH ~7.2.
- Pancreatic enzymes work best at alkaline pH (~8.5).
- Apoenzyme is an enzyme without its necessary cofactor and is inactive.
- Enzyme specificity depends on the 3D structure of the active site.
- Enzymes form peptide bonds between amino acids.
- Allosteric inhibition and negative feedback regulate enzyme activity.
- Competitive inhibition can be overcome by increasing substrate; noncompetitive cannot.
Human Physiology and Hormones
- ADH acts on water channels in the distal tubule and collecting duct to concentrate urine.
- Symptoms of Parkinson's disease are linked to decreased dopamine.
- Menopause leads to decreased osteoblast activity, increasing osteoporosis risk.
- Insulin levels are low during dehydration/starvation; ADH, cortisol, and aldosterone are elevated.
Genetics and Molecular Biology
- Crossing over occurs between non-sister chromatids during prophase I of meiosis.
- Hardy-Weinberg equilibrium requires all genes to confer similar reproductive advantages.
- DNA replication in bacteria does not require telomerase.
- Mitochondrial DNA is circular and self-replicating.
Cell Biology
- Golgi apparatus modifies and distributes proteins.
- The nucleolus synthesizes rRNA.
- Lysosomes are surrounded by a single membrane.
- Smooth ER is involved in lipid synthesis and detoxification, not protein synthesis.
- Prokaryotes lack a nucleus and membrane-bound organelles; ribosomal subunits differ.
Microbiology and Immunology
- Viruses can have single/double-stranded RNA or DNA genomes.
- Antibiotic resistance increases via conjugation and transduction, not binary fission.
- Innate immunity provides rapid response to endotoxins, independent of prior exposure.
Chemistry
- Empirical formulas use the lowest whole-number ratio of atoms.
- Law of constant composition states compounds have fixed element ratios regardless of source or phase.
- Ksp (solubility product) is only affected by temperature.
- Adding a catalyst changes reaction rate but not equilibrium position.
Physics
- Gravitational force is inversely proportional to distance squared.
- The medulla controls breathing.
- In a PV diagram, work is area under the curve; pressure-volume is not linearly decreasing.
- Sound waves are longitudinal and travel fastest through solids.
Psychology and Sociology
- The halo effect is a cognitive bias affecting judgments based on overall impression.
- Symbolic interactionism studies meaning via shared symbols (e.g., nodding for "yes").
- The foot-in-the-door technique gains compliance through escalating requests.
- Group polarization leads individuals to adopt more extreme positions after group discussions.
- Primary groups form strong, close bonds; secondary groups are more superficial.
- Culture lag is when cultural norms catch up slowly to technological advances.
- External locus of control attributes outcomes to outside factors.
- Race is physical features, ethnicity is cultural heritage, and culture is group lifestyle.
Key Terms & Definitions
- Apoenzyme — Enzyme without its cofactor, inactive form.
- Competitive inhibitor — Binds to the active site, can be overcome by extra substrate.
- Allosteric inhibition — Regulator binds outside active site, affecting enzyme activity.
- Feedback inhibition — End product inhibits an early pathway enzyme to control flux.
- Osteoclast/Osteoblast — Cells that resorb/form bone, respectively.
- Group polarization — Group discussion strengthens the average group opinion.
- Symbolic interactionism — Micro-level theory on shared symbols in social interaction.
- Empirical formula — Simplest whole-number ratio of atoms in a compound.
Action Items / Next Steps
- Review MCAT practice flashcards, focusing on reasoning behind answer choices.
- Study enzyme mechanisms, inhibition types, feedback loops, and basic cell biology.
- Practice converting word problems into chemical equations and calculations.
- Reflect on psychological and sociological concepts, especially bias and group dynamics.