Bio Exam II Practice Questions

The most direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation is A) oxidation of glucose to CO2 and water. B) the thermodynamically favorable flow of electrons from NADH to the mitochondrial electron transport carriers. C) the final transfer of electrons to oxygen. D) the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane. E) the thermodynamically favorable transfer of phosphate from glycolysis and the citric acid cycle intermediate molecules of ADP.

d

The ATP made during glycolysis is generated by A) substrate-level phosphorylation. B) electron transport. C) photophosphorylation. D) chemiosmosis. E) oxidation of NADH to NAD+.

substrate-level phosphorylation.

One carbon dioxide molecule reacts in each "turn" of the Calvin cycle. How many turns of the cycle are required for the synthesis of one glucose molecule? A) 1 B) 2 C) 3 D) 6 E) 12

d

When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation? A) Cells are open systems, but a test tube is a closed system. B) Cells are less efficient at heat production than nonliving systems. C) The hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube. D) The reaction in cells must be catalyzed by enzymes, but the reaction in a test tube does not need enzymes. E) Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat.

E

Which of the following statements is not representative of the second law of thermodynamics? A) Conversion of energy from one form to another is always accompanied by some loss of free energy. B) Heat represents a form of energy that cannot be used by most organisms to do work. C) Without an input of energy, organisms would tend towards increasing entropy. D) Cells require a constant input of energy to maintain their high level of organization. E) Every energy transformation by a cell decreases the entropy of the universe.

E

Which of the following statements regarding ATP is (are) correct? A) ATP serves as a main energy shuttle inside cells. B) ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants. C) The regeneration of ATP from ADP and phosphate is an endergonic reaction. D) A and B only E) A, B, and C

E

d

Figure 10.1 shows the absorption spectrum for chlorophyll a and the action spectrum for photosynthesis. Why are they different? A) Green and yellow wavelengths inhibit the absorption of red and blue wavelengths. B) Bright sunlight destroys photosynthetic pigments. C) Oxygen given off during photosynthesis interferes with the absorption of light. D) Other pigments absorb light in addition to chlorophyll a. E) Aerobic bacteria take up oxygen, which changes the measurement of the rate of photosynthesis.

d

Starting with one molecule of citrate and ending with oxaloacetate, how many ATP molecules can be formed from oxidative phosphorylation (chemiosmosis)? A) 1 B) 3 C) 4 D) 11 E) 12

b

Which of the following represents the activation energy required for the enzyme-catalyzed reaction? A) a B) b C) c D) d E) e

d

Which of the following would be the same in an enzyme-catalyzed or noncatalyzed reaction? A) a B) b C) c D) d E) e

CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they A) fix CO2 into organic acids during the night. B) fix CO2 into sugars in the bundle-sheath cells. C) fix CO2 into pyruvate in the mesophyll cells. D) use the enzyme phosphofructokinase, which out competes rubisco for CO2. E) use photosystems I and II at night.

a

During aerobic cellular respiration, a proton gradient in mitochondria is generated by ________ and used primarily for ________. A) the electron transport chain; ATP synthesis B) the electron transport chain; substrate-level phosphorylation C) glycolysis; production of H2O D) fermentation; NAD+ reduction E) diffusion of protons; ATP synthesis

a

Which of the following organic molecules cannot be easily converted to either a starting material for, or an intermediate of, glycolysis? A) fatty acids B) amino acids C) glucose and sucrose D) glycerol E) starch and glycogen

a

Which of the following statements describes the results of this reaction? C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy A) C6H12O6 is oxidized and O2 is reduced. B) O2 is oxidized and H2O is reduced. C) CO2 is reduced and O2 is oxidized. D) C6H12O6is reduced and CO2 is oxidized. E) O2 is reduced and CO2 is oxidized.

a

A series of enzymes catalyze the reaction X-->Y-->Z-->A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. 13) Substance A functions as A) a coenzyme. B) an allosteric inhibitor. C) the substrate. D) an intermediate. E) a competitive inhibitor.

b

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the G for the new reaction? A) -40 kcal/mol B) -20 kcal/mol C) 0 kcal/mol D) +20 kcal/mol E) +40 kcal/mol

b

From the perspective of the cell receiving the message, the three stages of cell signaling are A) the paracrine, local, and synaptic stages. B) signal reception, signal transduction, and cellular response. C) signal reception, nucleus disintegration, and new cell generation. D) the alpha, beta, and gamma stages. E) signal reception, cellular response, and cell division.

b

In the thylakoid membranes, what is the main role of the antenna pigment molecules? A) split water and release oxygen to the reaction-center chlorophyll B) harvest photons and transfer light energy to the reaction-center chlorophyll C) synthesize ATP from ADP and Pi D) transfer electrons to ferredoxin and then NADPH E) concentrate photons within the stroma

b

Testosterone functions inside a cell by A) acting as a signal receptor that activates ion-channel proteins. B) binding with a receptor protein that enters the nucleus and activates specific genes. C) acting as a steroid signal receptor that activates ion-channel proteins. D) becoming a second messenger that inhibits adenylyl cyclase. E) coordinating a phosphorylation cascade that increases glycogen metabolism.

b

The process of signal transduction usually begins A) when the second messenger is released into the cytosol. B) when the signal molecule changes the receptor protein in some way. C) after the target cell divides. D) after the third stage of cell signaling is completed. E) when the hormone is released from the gland into the blood.

b

The reaction-center chlorophyll of photosystem I is known as P700 because A) there are 700 chlorophyll molecules in the center. B) this pigment is best at absorbing light with a wavelength of 700 nm. C) there are 700 photosystem I components to each chloroplast. D) it absorbs 700 photons per microsecond. E) the plastoquinone reflects light with a wavelength of 700 nm.

b

What is the primary function of the light reactions of photosynthesis? A) to produce energy-rich glucose from carbon dioxide and water B) to produce ATP and NADPH C) to produce NADPH used in respiration D) to convert light energy to the chemical energy of PGAL E) to use ATP to make glucose

b

Which metabolic process is most closely associated with intracellular membranes? A) substrate-level phosphorylation B) oxidative phosphorylation C) glycolysis D) the citric acid cycle E) alcohol fermentation

b

Which of the following is (are) true regarding the activity of a protein regulated by phosphorylation? A) It depends mostly on the concentration of inorganic phosphate inside the cell. B) It depends on the balance in the cell between active kinase and active phosphatase molecules. C) It is dependent on the site of attachment of the protein to the plasma membrane. D) Only A and B are true. E) A, B, and C are true.

b

As a research scientist, you measure the amount of ATP and NADPH consumed by the Calvin cycle in 1 hour. You find 30,000 molecules of ATP consumed, but only 20,000 molecules of NADPH. Where did the extra ATP molecules come from? A) photosystem II B) photosystem I C) cyclic electron flow D) noncyclic electron flow E) chlorophyll

c

During glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is A) transferred to ADP, forming ATP. B) transferred directly to ATP. C) retained in the pyruvate. D) stored in the NADH produced. E) used to phosphorylate fructose to form fructose-6-phosphate.

c

In general, the most important way ATP energizes a cellular process is by A) releasing heat upon hydrolysis. B) acting as a catalyst. C) coupling free energy released by ATP hydrolysis to free energy needed by other reactions. D) lowering the activation energy of a chemical reaction. E) binding directly to the substrate(s) of the enzyme.

c

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? A) denaturization of the enzyme B) allosteric inhibition C) competitive inhibition D) saturation of the enzyme activity E) insufficient cofactors

c

The general name for an enzyme that transfers phosphate groups from ATP to a protein is A) ATP Synthase. B) phosphatase. C) protein kinase. D) ATPase. E) protease.

c

The major function of both alcohol fermentation and lactic acid fermentation is to A) reduce NAD+ to NADH. B) reduce FAD+ to FADH2. C) oxidize NADH to NAD+. D) reduce FADH2 to FAD+. E) none of the above

c

Where are the proteins of the electron transport chain located? A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix

c

Which of the following forms of energy is least available to accomplish cellular work? A) light energy B) chemical energy C) thermal energy (heat) D) mechanical energy E) potential energy

c

Which of the following is not part of the phosphorylation cascade model? A) It is a means to amplify the cellular response to the primary signal. B) Protein kinase(s) is (are) activated. C) IP3 donates a phosphate group to an inactive protein kinase. D) A specific protein (e.g. enzyme/transcription factor) is activated via phosphorylation. E) A cellular response is initiated.

c

Which of the following statements correctly describe(s) catabolic pathways? A) They do not depend on enzymes. B) They consume energy to build up polymers from monomers. C) They release energy as they degrade polymers to monomers. D) They lead to a net increase in free energy. E) Both A and B

c

All of the following are directly associated with photosystem II except A) extraction of hydrogen electrons from the splitting of water. B) release of oxygen. C) harvesting of light energy by chlorophyll. D) NADP+ reductase E) P680 reaction-center chlorophyll.

d

An inhibitor of which of the following would most directly block the release of calcium from the endoplasmic reticulum? A) tyrosine kinases B) serine/threonine kinases C) phosphodiesterase D) phospholipase C E) adenylyl cyclase

d

In a plant cell, where are the ATP synthase complexes located? A) thylakoid membrane B) plasma membrane C) inner mitochondrial membrane D) A and C E) A, B, and C

d

In comparing the light reactions with the Calvin cycle of photosynthesis in plants, which produces NADH? A) light reactions alone B) the Calvin cycle alone C) both the light reactions and the Calvin cycle D) neither the light reactions nor the Calvin cycle E) occurs in the chloroplast but is not part of photosynthesis

d

In general, how can one increase the rate of a chemical reaction? A) Increase the activation energy needed. B) Cool the reactants. C) Decrease the concentration of the reactants. D) Add a catalyst. E) Increase the entropy of the reactants.

d

All of the following are functions of the citric acid cycle except A) production of ATP. B) production of NADH. C) production of FADH2. D) release of carbon dioxide. E) adding electrons and protons to oxygen, forming water.

e

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to A) design a compound that blocks epinephrine receptor activation. B) design a compound that inhibits cAMP production in liver cells. C) design a compound to block G-protein activity in liver cells. D) design a compound that inhibits phosphorylase activity. E) All of the above are possible approaches.

e

In a typical cell, calcium ions are A) far more abundant in the blood and other extracellular fluid than in the cytoplasm. B) rapidly released from the endoplasmic reticulum in response to G-protein-mediated signals. C) often concentrated within the endoplasmic reticulum. D) A and B only E) A, B, and C

e

Muscle cells in oxygen deprivation convert pyruvate to ________, and in this step gain ________. A) lactate; ATP B) alcohol; CO2 C) alcohol; ATP D) ATP; NADH2 E) lactate; NAD+

e

The response of a particular cell to a signal depends on A) its particular collection of signal receptor proteins. B) its relay proteins. C) the proteins needed to carry out the response. D) A and B only E) A, B, and C

e

What is the change in free energy of a system at chemical equilibrium? A) slightly increasing B) greatly increasing C) slightly decreasing D) greatly decreasing E) no net change

e

What is the primary function of the Calvin cycle? A) use ATP to release carbon dioxide B) use NADPH to release carbon dioxide C) split water and release oxygen D) transport RuBP out of the chloroplast E) synthesize simple sugars from carbon dioxide

e

Which of the following is (are) true of ligand-gated ion channels? A) They are important in the nervous system. B) They lead to changes in sodium or calcium concentrations in cells. C) They open or close in response to a chemical signal. D) Only A and B are true. E) A, B, and C are true.

e

Which of the following is (are) widely used second messenger(s) in signal transduction pathways? A) calcium ions B) cyclic AMP C) inositol trisphosphate (IP3) D) A and B only E) A, B, and C

e

Which of the following statements about the light reactions of photosynthesis is (are) true? A) The splitting of water molecules provides a source of electrons. B) Chlorophyll (and other pigments) absorbs light energy, which excites electrons. C) ATP is generated by photophosphorylation. D) Only A and C are true. E) A, B, and C are true.

e

Which of the following statements is (are) correct about an oxidation-reduction (or redox) reaction? A) The molecule that is reduced gains electrons. B) The molecule that is oxidized loses electrons. C) The molecule that is reduced loses electrons. D) The molecule that is oxidized gains electrons. E) Both A and B are correct.

e