BIO 181 Exam Review: Macromolecules, Cells, Metabolism and Genetics

Terms in this set (31)

1. What are the four major classes of biological macromolecules?Carbohydrates, lipids, proteins and nucleic acids. All but lipids are true polymers built from repeating monomers.
2. What type of reaction links monomers into polymers, and what reaction breaks them apart?Dehydration synthesis (condensation) joins monomers by removing a water molecule; hydrolysis breaks the bond by adding water.
3. Name the four levels of protein structure.Primary: amino acid sequence. Secondary: alpha helices and beta sheets from backbone hydrogen bonds. Tertiary: overall 3D fold from R-group interactions. Quaternary: association of multiple polypeptide subunits.
4. Saturated vs unsaturated fatty acidsSaturated fatty acids have no C=C double bonds and pack tightly (solid at room temperature). Unsaturated fatty acids have one or more cis double bonds that create kinks, keeping them liquid.
5. Why is water such a good solvent, and what gives it high cohesion?Water is polar, so it surrounds ions and polar molecules. Hydrogen bonds between water molecules produce cohesion, surface tension and a high specific heat.
6. Prokaryotic vs eukaryotic cellsProkaryotes (bacteria, archaea) lack a nucleus and membrane-bound organelles and have 70S ribosomes. Eukaryotes have a nucleus, membrane-bound organelles and 80S cytoplasmic ribosomes.
7. What does the endosymbiotic theory propose?Mitochondria and chloroplasts descended from free-living prokaryotes engulfed by an ancestral cell. Evidence: their own circular DNA, double membranes, 70S-like ribosomes and division by binary fission.
8. Trace the path of a secreted protein through the endomembrane system.Synthesized by ribosomes on the rough ER, moved in vesicles to the Golgi for modification and sorting, then carried in secretory vesicles to the plasma membrane for exocytosis.
9. What does the fluid mosaic model describe?The plasma membrane as a fluid phospholipid bilayer with proteins, cholesterol and carbohydrates embedded or attached that can move laterally.
10. Diffusion vs facilitated diffusion vs active transportDiffusion: solutes cross the bilayer down their gradient with no protein. Facilitated diffusion: down the gradient through channel or carrier proteins, no ATP. Active transport: against the gradient using energy, such as ATP.
11. A red blood cell is placed in a hypotonic solution. What happens?Water moves into the cell by osmosis because the outside has a lower solute concentration, so the cell swells and may lyse.
12. What does the sodium-potassium pump do per ATP used?It pumps 3 Na+ out of the cell and 2 K+ into the cell, maintaining gradients and a negative membrane potential.
13. How do enzymes speed up reactions?They lower the activation energy by stabilizing the transition state. They do not change delta G or the equilibrium position, and they are not consumed.
14. Competitive vs noncompetitive inhibitionA competitive inhibitor binds the active site and can be overcome by more substrate. A noncompetitive inhibitor binds elsewhere (allosteric site), changing the enzyme's shape, so extra substrate does not overcome it.
15. Exergonic vs endergonic reactionsExergonic reactions release free energy (delta G < 0) and are spontaneous. Endergonic reactions require energy (delta G > 0) and are often driven by coupling to ATP hydrolysis.
16. Overall equation for cellular respirationC6H12O6 + 6 O2 -> 6 CO2 + 6 H2O + energy (ATP and heat).
17. Where do glycolysis, the citric acid cycle and the electron transport chain occur in eukaryotes?Glycolysis: cytosol. Pyruvate oxidation and the citric acid cycle: mitochondrial matrix. Electron transport chain and ATP synthase: inner mitochondrial membrane.
18. What is chemiosmosis?Using energy from electron transport to pump H+ across a membrane, then letting H+ flow back down its gradient through ATP synthase to make ATP.
19. What is the role of oxygen in aerobic respiration?Oxygen is the final electron acceptor of the electron transport chain; it combines with electrons and H+ to form water.
20. What is the purpose of fermentation?To regenerate NAD+ from NADH so glycolysis can continue making ATP without oxygen. Products include lactate (animals) or ethanol and CO2 (yeast).
21. Light reactions vs Calvin cycleLight reactions (thylakoid membranes) use light to split water, release O2 and make ATP and NADPH. The Calvin cycle (stroma) uses that ATP and NADPH to fix CO2 into sugar via the enzyme rubisco.
22. List the phases of mitosis in order.Prophase, prometaphase, metaphase, anaphase, telophase, usually followed by cytokinesis.
23. Key differences between mitosis and meiosisMitosis: one division producing 2 genetically identical diploid cells. Meiosis: two divisions producing 4 genetically different haploid cells, with crossing over and independent assortment.
24. When does crossing over occur and why does it matter?During prophase I of meiosis, between homologous chromosomes. It exchanges DNA segments, creating new allele combinations.
25. Cross Aa x Aa (A dominant). What are the expected genotype and phenotype ratios?Genotypes 1 AA : 2 Aa : 1 aa. Phenotypes 3 dominant : 1 recessive.
26. State Mendel's law of segregation and law of independent assortment.Segregation: the two alleles of a gene separate into different gametes. Independent assortment: alleles of genes on different chromosomes sort into gametes independently of each other.
27. Describe the structure of DNA.A double helix of two antiparallel strands with a sugar-phosphate backbone. Bases pair by hydrogen bonds: A with T (2 bonds) and G with C (3 bonds).
28. Why is DNA replication called semiconservative?Each new double helix contains one original parental strand and one newly synthesized strand, as shown by the Meselson-Stahl experiment.
29. Leading vs lagging strand in DNA replicationDNA polymerase only adds nucleotides 5' to 3'. The leading strand is made continuously toward the fork; the lagging strand is made in Okazaki fragments joined by DNA ligase.
30. State the central dogma and where each step occurs in eukaryotes.DNA -> RNA -> protein. Transcription occurs in the nucleus; translation occurs at ribosomes in the cytoplasm.
31. A codon reads 5'-AUG-3'. What does it code for?Methionine; AUG is also the start codon. The genetic code is read in triplets, and UAA, UAG and UGA are stop codons.