Exam 3
Chapter 10: Lipids and Membranes
1. Q: What is the main difference between membrane lipids and storage lipids?
- A: Membrane lipids are structural components of cellular membranes, while storage lipids (like triacylglycerols) serve as energy reserves.
2. Q: How does chain length and saturation affect the melting point of fatty acids?
- A: Longer chains increase melting point, and saturated fats have higher melting points than unsaturated fats.
3. Q: What are the main types of lipids, and what is an example of each?
- A: Phospholipids (e.g., phosphatidylcholine), sphingolipids (e.g., sphingomyelin), glycolipids, waxes, and sterols (e.g., cholesterol).
4. Q: What is a distinguishing feature of sphingolipids compared to phospholipids?
- A: Sphingolipids have a sphingosine backbone, while phospholipids have a glycerol backbone.
5. Q: What are the four main types of membrane phospholipids, and why are they important?
- A: Phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), and sphingomyelin (SM); they contribute to membrane structure and function.
6. Q: Describe the three types of membrane proteins.
- A: Integral (span the bilayer), peripheral (loosely attached to membrane surfaces), and anchored (covalently attached to lipids or carbohydrates on the membrane).
7. Q: How do anchored proteins differ from integral and peripheral proteins?
- A: Anchored proteins are attached to the membrane via covalently bound lipids or carbohydrates, while integral proteins span the bilayer and peripheral proteins attach loosely to the surface.
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### Chapter 11: Lipid Structures and Membrane Dynamics
1. Q: What are the primary structures that lipids form in water?
- A: Monolayers, micelles, bilayers, and vesicles.
2. Q: What role does cholesterol play in membrane fluidity?
- A: Cholesterol modulates membrane fluidity by making membranes less permeable and stabilizing them at varying temperatures.
3. Q: What is the fluid mosaic model?
- A: A model describing the membrane as a flexible layer with proteins embedded within or associated with the lipid bilayer.
4. Q: What is membrane asymmetry?
- A: The distribution of lipids and proteins differs between the inner and outer leaflets of the bilayer, which affects membrane function.
5. Q: What functions do flippase, floppase, and scramblase serve in a cell membrane?
- A: They are enzymes that help move lipids between membrane leaflets: flippase and floppase move specific lipids in one direction, while scramblase moves lipids bidirectionally.
6. Q: What types of molecules can pass freely through a lipid bilayer, and which require transporters?
- A: Small, nonpolar molecules can pass freely, while ions and polar molecules typically require transporters.
7. Q: Describe the purpose of a FRAP experiment.
- A: FRAP (Fluorescence Recovery After Photobleaching) measures lipid mobility within the bilayer by tracking the recovery of fluorescence.
8. Q: What is the Kennedy-Rothman experiment, and what does it study?
- A: It studies vesicle fusion with membranes, helping to understand lipid and protein dynamics in membranes.
9. Q: What are lipid rafts, and what is their function?
- A: Lipid rafts are microdomains rich in cholesterol and sphingolipids that organize signaling proteins and membrane trafficking.
10. Q: How are membrane transporters classified?
- A: Transporters are classified as symport (same direction), antiport (opposite directions), and uniport (single substance transport).
11. Q: How do you calculate Km and kcat for a transporter?
- A: By using the Michaelis-Menten equation, which models the rate of substrate transport.
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### Chapter 8: Nucleic Acids
1. Q: What are the five nucleobases in nucleic acids?
- A: Adenine (A), Thymine (T), Guanine (G), Cytosine (C), and Uracil (U).
2. Q: What components make up a nucleotide?
- A: A phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base.
3. Q: What is the difference between a nucleotide, nucleoside, and nucleobase?
- A: A nucleotide includes the phosphate, sugar, and base; a nucleoside is only the sugar and base; and a nucleobase is just the base.
4. Q: What are the base-pairing rules in DNA?
- A: Adenine pairs with Thymine (A-T), and Guanine pairs with Cytosine (G-C).
5. Q: What is the structure of double-stranded DNA?
- A: It is an antiparallel double helix with base-stacking interactions between paired bases.
6. Q: What role does DNA polymerase play in replication?
- A: DNA polymerase synthesizes DNA in the 5' to 3' direction, requiring a primer and Mg²⁺ ions.
7. Q: What are the key steps and reagents for PCR?
- A: Denaturation, annealing, and extension, with DNA template, primers, nucleotides, and DNA polymerase.
8. Q: What is Sanger sequencing used for?
- A: It determines DNA sequence using dideoxynucleotides to terminate replication at specific bases.
9. Q: How does DNA electrophoresis work?
- A: It separates DNA fragments by size as they move through a gel in an electric field.
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### Chapter 13: Bioenergetics and Redox Chemistry
1. Q: How do you identify a redox reaction?
- A: Look for changes in oxidation states, where one species is oxidized (loses electrons) and another is reduced (gains electrons).
2. Q: What distinguishes high-energy from low-energy phosphoryl and carbonyl groups?
- A: High-energy groups release more free energy upon hydrolysis compared to low-energy groups.
3. Q: What makes ATP a reactive molecule?
- A: ATP contains high-energy phosphoanhydride bonds that release energy when hydrolyzed.
4. Q: Why is coupling reactions important in bioenergetics?
- A: Coupling allows non-spontaneous reactions to occur by pairing them with spontaneous reactions, making the overall process favorable.
5. Q: How do you calculate ΔG for a reaction?
- A: Use the equation ΔG = ΔG°' + RT lnQ, or by summing ΔG values for coupled reactions.
6. Q: How do you find ΔG from Keq?
- A: ΔG°' = -RT lnKeq, which relates standard free energy to the equilibrium constant.
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These flashcards should be handy for quick review and to quiz yourself chapter by chapter!