Unit 2

1. Chapters 6-10 Unit 2

2. Which cellular structure is common to all 3 domains of life? • Nucleus • Endoplasmic reticulum • Mitochondria • Phospholipid bilayer cell membrane • Endocytotic vesicles

3. Difference between Plant and Animal CellsWhich of these organelles are absent in plant cells? • mitochondria • centrioles • microtubules • all of the above • none of the above

4. Enzymes responsible for biosynthesis of membrane lipids would be located in what part of the cell? • endoplasmic reticulum. • nucleus. • lysosomes. • Golgi. • plasma membrane

5. According to the endosymbiont theory, which of the following organelles were once endosymbiotic prokaryotic organisms? • Mitochondria and lysosomes • Mitochondria and chloroplasts • Chloroplasts and Golgi apparatus • Golgi apparatus and ribosomes • Ribosomes and lysosomes

6. Microtubule Function Taxol, a drug approved for treatment of breast cancer, prevents depolymerization of microtubules. What cellular function that affects cancer cells more than normal cells might taxol interfere with? • maintaining cell shape • cilia or flagella • chromosome movements in cell division • cell division (cleavage furrow formation) • cytoplasmic streaming

7. Which of the following is not an argument for the theory that mitochondria and chloroplasts evolved from prokaryotic endosymbionts? • Mitochondria and chloroplasts have double membranes. • Mitochondria and chloroplasts have their own ribosomes. • Mitochondria and chloroplasts have their own DNA. • The mitochondrial and chloroplast genomes are circular. • All of the above support the endosymbiotic theory.

8. ECM in Plant and Animal CellsThe difference in the structures of animal cell extracellular matrix and plant cell walls reflects what fundamental difference(s) in their adaptive strategies? • Animal cells must move more than plant cells. • Animal cells have to be more responsive to changes in their environment. • Animal cells have to communicate with each other more than plant cells. • all of the above

9. Membrane Structure • Which of the following best describes the structure of a biologicalmembrane? • two layers of phospholipids with proteins embedded between the two layers • a mixture of covalently linked phospholipids and proteins that determines which solutes can cross the membrane and which cannot • two layers of phospholipids with proteins either crossing the layers or on the surface of the layers • a fluid structure in which phospholipids and proteins move freely between sides of the membrane • two layers of phospholipids (with opposite orientations of the phospholipids in each layer) with each layer covered on the outside with proteins

10. Osmosis • Which of the following statements about osmosis is correct? • a) If a cell is placed in an isotonic solution, more water will enter the cell than leaves the cell. • b) Osmotic movement of water into a cell would likely occur if the cell accumulates water from its environment. • c) The presence of aquaporins (proteins that form water channels in the membrane) should speed up the process of osmosis. • d) If a solution outside the cell is hypertonic compared to the cytoplasm, water will move into the cell by osmosis. • e) Osmosis is the diffusion of water from a region of lower water concentration to a region of higher water concentration.

11. Transmembrane DomainsWhich of the following amino acids would most likely be present in the transmembrane domain of an integral membrane protein? • a charged amino acid like lysine • a polar amino acid like serine • a special amino acid like glycine or proline • a hydrophobic amino acid like valine • any of the above, with no preference

12. Membrane PermeabilityWhich of the following molecules will diffuse most quickly across a lipid bilayer membrane? • H2O • O2 • H2PO4– • glucose • Na+

13. OsmosisIf a marine algal cell is suddenly transferred from seawater to freshwater, the algal cell will initially • lose water and decrease in volume. • stay the same: neither absorb nor lose water. • absorb water and increase in volume.

14. Transport Kinetics: Passive DiffusionWhich of the curves below illustrates uptake of nitrous oxide into the cell, if nitrous oxide diffuses passively across the membrane? • A • B • C

15. Transport Kinetics: Passive DiffusionWhich of the curves below illustrates uptake of phosphate into the cell by an active transport system? • A • B • C

16. Living Organisms and Order The laws of thermodynamics do not apply to living organisms. Living organisms create order by using energy from the sun. Living organisms create order locally, but the energy transformations generate waste heat that increases the entropy of the universe. How do living organisms create macromolecules, organelles, cells, tissues, and complex higher-order structures?

17. Free Energy The reaction could be coupled to power an endergonic reaction with a G of 8.8 kcal/mol. The reaction would result in a decrease in entropy (S) and an increase in the energy content (H) of the system. The reaction would result in an increase in entropy (S) and a decrease in the energy content (H) of the system. The reaction would result in products with a greater free-energy content than in the initial reactants. A reaction has a ∆G of 5.6 kcal/mol. Which of the following would most likely be true?

18. Rate of a Chemical Reaction The glucose molecules lack the activation energy at room temperature. There is too much CO2 in the air. CO2 has higher energy than glucose. The formation of six CO2 molecules from one glucose molecule decreases entropy. The water molecules quench the reaction. The oxidation of glucose to CO2 and H2O is highly exergonic: G = –636 kcal/mole. Why doesn’t glucose spontaneously combust?

19. Enzyme-Catalyzed Reactions a b c d e In the energy diagram below, which of the lettered energy changes would be the same in both the enzyme-catalyzed and uncatalyzed reactions?

20. If this is an enzyme-catalyzed reaction, how can the rate of this reaction be increased beyond the maximum velocity in this figure? Increase the substrate concentrations. Increase the amount of enzyme. Increase the amount of energy. any of the above There is no way to increase the rate of the reaction any further.

21. Enzyme Inhibitors competitive inhibitors. noncompetitive inhibitors. allosteric regulators. prosthetic groups. feedback inhibitors. Vioxx and other prescription nonsteroidal anti-inflammatory drugs (NSAIDs) are potent inhibitors of the cycloxygenase-2 (COX-2) enzyme. High substrate concentrations reduce the efficacy of inhibition by these drugs. These drugs are

22. Enzyme Regulation cooperative activation. allosteric activation. activation by an enzyme cofactor. coupling exergonic and endergonic reactions. Adenosine monophosphate (AMP) activates the enzyme phosphofructokinase (PFK) by binding at a site distinct from the substrate binding site. This is an example of

23. During glycolysis, for each glucose oxidized to pyruvate • 6 ATP are produced. • 4 ATP are used, and 2 ATP are produced. • 2 ATP are used, and 4 ATP are produced. • 2 ATP are used, and 2 ATP are produced. • net 4 ATP are produced.

24. GlycolysisTo sustain high rates of glycolysis under anaerobic conditions, cells require • functioning mitochondria. • oxygen. • oxidative phosphorylation of ATP. • NAD+. • All of the above are correct.

25. Drugs known as uncouplers facilitate diffusion of protons across the membrane. When such a drug is added, what will happen to ATP synthesis and oxygen consumption, if the rates of glycolysis and the citric acid cycle stay the same? • Both ATP synthesis and oxygen consumption will decrease. • ATP synthesis will decrease; oxygen consumption will increase. • ATP synthesis will increase; oxygen consumption will decrease. • Both ATP synthesis and oxygen consumption will increase. • ATP synthesis will decrease; oxygen consumption will stay the same.