Mbio study
In alcohol fermentation, NAD+ is regenerated from NADH during which of the following? A) reduction of acetaldehyde to ethanol (ethyl alcohol) B) oxidation of pyruvate to acetyl CoA C) reduction of pyruvate to form lactate D) oxidation of NAD+ in the citric acid cycle E) phosphorylation of ADP to form ATP
A
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is A) oxygen. B) water. C) NAD+. D) pyruvate. E) ADP.
A
Which of the following bests describes the reaction? A) negative △G, spontaneous B) positive △G, nonspontaneous C) positive △G, exergonic D) negative △G, endergonic E) △G of zero, chemical equilibrium
A
Which step consists of a phosphorylation reaction in which ATP is the phosphate source?
A
An electron loses potential energy when it A) shifts to a less electronegative atom. B) shifts to a more electronegative atom. C) increases its kinetic energy. D) increases its activity as an oxidizing agent. E) attaches itself to NAD+.
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
B
Which of the following statements is true concerning catabolic pathways? A) They combine molecules into more energy-rich molecules. B) They are usually coupled with anabolic pathways to which they supply energy in the form of ATP. C) They are endergonic. D) They are spontaneous and do not need enzyme catalysis. E) They build up complex molecules such as protein from simpler compounds.
B
In addition to ATP, what are the end products of glycolysis? A) CO2 and H2O B) CO2 and pyruvate C) NADH and pyruvate D) CO2 and NADH E) H2O, FADH2, and citrate
C
Assume a mitochondrion contains 58 NADH and 19 FADH2. If each of the 77 dinucleotides were used, approximately how many ATP molecules could be generated as a result of oxidative phosphorylation (chemiosmosis)? A) 36 B) 77 C) 173 D) 212 E) 1102
D
Where is ATP synthase located in the mitochondrion? A) cytosol B) electron transport chain C) outer membrane D) inner membrane E) mitochondrial matrix
D
Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate? A) lactate B) glyceraldehydes-3-phosphate C) oxaloacetate D) acetyl CoA E) citrate
D
Which of the following represents the △G of the reaction? A) a B) b C) c D) d E) e
D
The sequestering of carbon in CAM plants helps them to survive by
allowing carbon dioxide to be gathered and used at different times of the day
A chemical reaction that has a positive △G is correctly described as A) endergonic. B) endothermic. C) enthalpic. D) spontaneous. E) exothermic.
A
A young animal has never had much energy. He is brought to a veterinarian for help and is sent to the animal hospital for some tests. There they discover his mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of his condition? A) His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane. B) His cells cannot move NADH from glycolysis into the mitochondria. C) His cells contain something that inhibits oxygen use in his mitochondria. D) His cells lack the enzyme in glycolysis that forms pyruvate. E) His cells have a defective electron transport chain, so glucose goes to lactate instead of to acetyl CoA.
A
Among enzymes, kinases catalyze phosphorylation, while phosphatases catalyze removal of phosphate(s). A cell's use of these enzymes can therefore function as an on-off switch for various processes. Which of the following is probably involved? A) the change in a protein's charge leading to a conformational change B) the change in a protein's charge leading to cleavage C) a change in the optimal pH at which a reaction will occur D) a change in the optimal temperature at which a reaction will occur E) the excision of one or more peptides
A
Competitive inhibitors block the entry of substrate into the active site of an enzyme. On which of the following properties of an active site does this primarily depend? A) the ability of an enzyme to form a template for holding and joining molecules B) the enzyme's ability to stretch reactants and move them toward a transition state C) the enzyme providing an appropriate microenvironment conducive to a reaction's occurrence D) the enzyme forming covalent bonds with the reactants E) the enzyme becoming too saturated because of the concentration of substrate
A
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If the membranes are agitated still further however, the ability to synthesize ATP is lost. 65) After the first disruption, when electron transfer and ATP synthesize still occur, what must be present? A) all of the electron transport proteins as well as ATP synthase B) all of the electron transport system and the ability to add CoA to acetyl groups C) the ATP synthase system is sufficient D) the electron transport system is sufficient E) plasma membranes like those bacteria use for respiration Answer:
A
Glycolysis is thought to be one of the most ancient of metabolic processes. Which statement supports this idea? A) Glycolysis is the most widespread metabolic pathway. B) Glycolysis neither uses nor needs O2. C) Glycolysis is found in all eukaryotic cells. D) The enzymes of glycolysis are found in the cytosol rather than in a membrane-enclosed organelle. E) Ancient prokaryotic cells, the most primitive of cells, made extensive use of glycolysis long before oxygen was present in Earth's atmosphere.
A
How does pyruvate enter the mitochondrion? A) active transport B) diffusion C) facilitated diffusion D) through a channel E) through a pore
A
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate? A) 2 B) 4 C) 6 D) 8 E) 10
A
If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to A) add more of the enzyme. B) heat the solution to 90°C. C) add more substrate. D) add an allosteric inhibitor. E) add a noncompetitive inhibitor.
A
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of A) ATP, CO2, and ethanol (ethyl alcohol). B) ATP, CO2, and lactate. C) ATP, NADH, and pyruvate. D) ATP, pyruvate, and oxygen. E) ATP, pyruvate, and acetyl CoA.
A
Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount ATP in a cell would be expected to A) inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle. B) activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle. C) inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle. D) activate the enzyme and increase the rates of glycolysis and the citric acid cycle. E) inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate.
A
Starting with one molecule of isocitrate and ending with fumarate, what is the maximum number of ATP molecules that could be made through substrate-level phosphorylation? A) 1 B) 2 C) 11 D) 12 E) 24
A
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+.
A
The organization of organisms has become increasingly complex with time. This statement A) is consistent with the second law of thermodynamics. B) requires that due to evolution, the entropy of the universe increased. C) is based on the fact that organisms function as closed systems. D) A and B only E) A, B, and C
A
What is the purpose of using malonic acid in this experiment? A) It is a competitive inhibitor. B) It blocks the binding of fumarate. C) It is a noncompetitive inhibitor. D) It is able to bind to succinate. E) It replaces the usual enzyme.
A
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs? A) The pH of the matrix increases. B) ATP synthase pumps protons by active transport. C) The electrons gain free energy. D) The cytochromes phosphorylate ADP to form ATP. E) NAD+ is oxidized.
A
Which of the following is a statement of the first law of thermodynamics? A) Energy cannot be created or destroyed. B) The entropy of the universe is decreasing. C) The entropy of the universe is constant. D) Kinetic energy is stored energy that results from the specific arrangement of matter. E) Energy cannot be transferred or transformed.
A
Which of the following is considered an open system? A) an organism B) liquid in a corked bottle C) a sealed terrarium D) food cooking in a pressure cooker
A
Which of the following normally occurs whether or not oxygen (O2) is present? A) glycolysis B) fermentation C) oxidation of pyruvate to acetyl CoA D) citric acid cycle E) oxidative phosphorylation (chemiosmosis)
A
Which of the following occurs in the cytosol of a eukaryotic cell? A) glycolysis and fermentation B) fermentation and chemiosmosis C) oxidation of pyruvate to acetyl CoA D) citric acid cycle E) oxidative phosphorylation
A
Which of the following statements describes NAD+? A) NAD+ is reduced to NADH during both glycolysis and the citric acid cycle. B) NAD+ has more chemical energy than NADH. C) NAD+ is reduced by the action of hydrogenases. D) NAD+ can donate electrons for use in oxidative phosphorylation. E) In the absence of NAD+, glycolysis can still function.
A
Which of the following statements describes the results of this reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 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) C6H12O6 is reduced and CO2 is oxidized. E) O2 is reduced and CO2 is oxidized.
A
Which of the following statements is (are) true about enzyme-catalyzed reactions? A) The reaction is faster than the same reaction in the absence of the enzyme. B) The free energy change of the reaction is opposite from the reaction in the absence of the enzyme. C) The reaction always goes in the direction toward chemical equilibrium. D) A and B only E) A, B, and C
A
Which of the following types of reactions would decrease the entropy within a cell? A) dehydration reactions B) hydrolysis C) respiration D) digestion E) catabolism
A
Which step involves an endergonic reaction?
A
You have a friend who lost 7 kg (about 15 pounds) of fat on a "low carb" diet. How did the fat leave her body? A) It was released as CO2 and H2O. B) Chemical energy was converted to heat and then released. C) It was converted to ATP, which weighs much less than fat. D) It was broken down to amino acids and eliminated from the body. E) It was converted to urine and eliminated from the body.
A
In the diagram, which molecule is best represented by the letter C?
ATP
What are the two main products of the light-capturing reaction of photosynthesis?
ATP and NADPH
Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity? A) cessation of all enzyme formation B) compartmentalization of enzymes into defined organelles C) exporting enzymes out of the cell D) connecting enzymes into large aggregates E) hydrophobic interactions
B
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration? A) glycolysis and the oxidation of pyruvate to acetyl CoA B) oxidation of pyruvate to acetyl CoA and the citric acid cycle C) the citric acid cycle and oxidative phosphorylation D) oxidative phosphorylation and fermentation E) fermentation and glycolysis
B
Cellular respiration harvests the most chemical energy from which of the following? A) substrate-level phosphorylation B) chemiosmotic phosphorylation C) converting oxygen to ATP D) transferring electrons from organic molecules to pyruvate E) generating carbon dioxide and oxygen in the electron transport chain
B
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________. A) exergonic; spontaneous B) exergonic; endergonic C) free energy; entropy D) work; energy E) entropy; enthalpy
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
During aerobic respiration, electrons travel downhill in which sequence? A) food → citric acid cycle → ATP → NAD+ B) food → NADH → electron transport chain → oxygen C) glucose → pyruvate → ATP → oxygen D) glucose → ATP → electron transport chain → NADH E) food → glycolysis → citric acid cycle → NADH → ATP
B
For living organisms, which of the following is an important consequence of the first law of thermodynamics? A) The energy content of an organism is constant. B) The organism ultimately must obtain all of the necessary energy for life from its environment. C) The entropy of an organism decreases with time as the organism grows in complexity. D) Organisms are unable to transform energy. E) Life does not obey the first law of thermodynamics.
B
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction? A) by binding at the active site of the enzyme B) by changing the shape of a reactant C) by changing the free energy change of the reaction D) by acting as a coenzyme for the reaction E) by decreasing the activation energy of the reaction
B
In glycolysis, for each molecule of glucose oxidized to pyruvate A) 2 molecules of ATP are used and 2 molecules of ATP are produced. B) 2 molecules of ATP are used and 4 molecules of ATP are produced. C) 4 molecules of ATP are used and 2 molecules of ATP are produced. D) 2 molecules of ATP are used and 6 molecules of ATP are produced. E) 6 molecules of ATP are used and 6 molecules of ATP are produced.
B
In order to attach a particular amino acid to the tRNA molecule that will transport it, an enzyme, an aminoacyl-tRNA synthetase, is required, along with ATP. Initially, the enzyme has an active site for ATP and another for the amino acid, but it is not able to attach the tRNA. What must occur in order for the final attachment to occur? A) The ATP must first have to attach to the tRNA. B) The binding of the first two molecules must cause a 3-dimensional change that opens another active site on the enzyme. C) The hydrolysis of the ATP must be needed to allow the amino acid to bind to the synthetase. D) The tRNA molecule must have to alter its shape in order to be able to fit into the active site with the other two molecules. E) The 3' end of the tRNA must have to be cleaved before it can have an attached amino acid.
B
It is possible to prepare vesicles from portions of the inner membrane of the mitochondrial components. Which one of the following processes could still be carried on by this isolated inner membrane? A) the citric acid cycle B) oxidative phosphorylation C) glycolysis and fermentation D) reduction of NAD+ E) both the citric acid cycle and oxidative phosphorylation
B
Most CO2 from catabolism is released during A) glycolysis. B) the citric acid cycle. C) lactate fermentation. D) electron transport. E) oxidative phosphorylation.
B
Pyruvate + NADH + H+ → Lactate + NAD+ A) oxygen B) NADH C) NAD+ D) lactate E) pyruvate
B
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's A) entropy. B) activation energy. C) endothermic level. D) heat content. E) free-energy content.
B
Starting with one molecule of glucose, the "net" products of glycolysis are A) 2 NAD+, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O. B) 2 NADH, 2 H+, 2 pyruvate, 2 ATP, and 2 H2O. C) 2 FADH2, 2 pyruvate, 4 ATP, and 2 H2O. D) 6 CO2, 6 H2O, 2 ATP, and 2 pyruvate. E) 6 CO2, 6 H2O, 36 ATP, and 2 citrate.
B
Substance A functions as A) a coenzyme. B) an allosteric inhibitor. C) the substrate. D) an intermediate. E) a competitive inhibitor.
B
The ATP made during fermentation is generated by which of the following? A) the electron transport chain B) substrate-level phosphorylation C) chemiosmosis D) oxidative phosphorylation E) aerobic respiration
B
The active site of an enzyme is the region that A) binds allosteric regulators of the enzyme. B) is involved in the catalytic reaction of the enzyme. C) binds the products of the catalytic reaction. D) is inhibited by the presence of a coenzyme or a cofactor.
B
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as A) metabolic inhibition. B) feedback inhibition. C) allosteric inhibition. D) noncooperative inhibition. E) reversible inhibition.
B
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction A) gains electrons and gains energy. B) loses electrons and loses energy. C) gains electrons and loses energy. D) loses electrons and gains energy. E) neither gains nor loses electrons, but gains or loses energy.
B
The oxygen consumed during cellular respiration is involved directly in which process or event? A) glycolysis B) accepting electrons at the end of the electron transport chain C) the citric acid cycle D) the oxidation of pyruvate to acetyl CoA E) the phosphorylation of ADP to form ATP
B
The primary role of oxygen in cellular respiration is to A) yield energy in the form of ATP as it is passed down the respiratory chain. B) act as an acceptor for electrons and hydrogen, forming water. C) combine with carbon, forming CO2. D) combine with lactate, forming pyruvate. E) catalyze the reactions of glycolysis.
B
What is proton-motive force? A) the force required to remove an electron from hydrogen B) the transmembrane proton concentration gradient C) movement of hydrogen into the intermembrane space D) movement of hydrogen into the mitochondrion E) the addition of hydrogen to NAD+
B
What is the term for metabolic pathways that release stored energy by breaking down complex molecules? A) anabolic pathways B) catabolic pathways C) fermentation pathways D) thermodynamic pathways E) bioenergetic pathways
B
When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows: A) +△G, +△H, +△S B) +△G, +△H, -△S C) +△G, -△H, -△S D) -△G, +△H, +△S E) -△G, -△H, -△S
B
When muscle cells are oxygen deprived, the heart still pumps. What must the heart cells be able to do? A) derive sufficient energy from fermentation B) continue aerobic metabolism when skeletal muscle cannot C) transform lactate to pyruvate again D) remove lactate from the blood E) remove oxygen from lactate
B
Which of the following best describes enthalpy (H)? A) the total kinetic energy of a system B) the heat content of a chemical system C) the system's entropy D) the cell's energy equilibrium E) the condition of a cell that is not able to react
B
Which of the following describes ubiquinone? A) a protein in the electron transport chain B) a small hydrophobic coenzyme C) a substrate for synthesis of FADH D) a vitamin needed for efficient glycolysis E) an essential amino acid
B
Which of the following is a true distinction between fermentation and cellular respiration? A) Only respiration oxidizes glucose. B) NADH is oxidized by the electron transport chain in respiration only. C) Fermentation, but not respiration, is an example of a catabolic pathway. D) Substrate-level phosphorylation is unique to fermentation. E) NAD+ functions as an oxidizing agent only in respiration.
B
Which of the following is likely to lead to an increase in the concentration of ATP in a cell? A) an increase in a cell's anabolic activity B) an increase in a cell's catabolic activity C) an increased influx of cofactor molecules D) an increased amino acid concentration E) the cell's increased transport of materials to the environment
B
Which of the following is true for all exergonic reactions? A) The products have more total energy than the reactants. B) The reaction proceeds with a net release of free energy. C) Some reactants will be converted to products. D) A net input of energy from the surroundings is required for the reactions to proceed. E) The reactions are nonspontaneous.
B
Which of the following metabolic processes can occur without a net influx of energy from some other process? A) ADP + Pi → ATP + H2O B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O C) 6 CO2 + 6 H2O → C6H12O6 + 6 O2 D) amino acids → protein E) glucose + fructose → sucrose
B
Which of the following most accurately describes what is happening along this chain? A) Chemiosmosis is coupled with electron transfer. B) Each electron carrier alternates between being reduced and being oxidized. C) ATP is generated at each step. D) Energy of the electrons increases at each step. E) Molecules in the chain give up some of their potential energy.
B
Which of the following statements regarding enzymes is true? A) Enzymes decrease the free energy change of a reaction. B) Enzymes increase the rate of a reaction. C) Enzymes change the direction of chemical reactions. D) Enzymes are permanently altered by the reactions they catalyze. E) Enzymes prevent changes in substrate concentrations.
B
Which of the following terms best describes the reaction? A) endergonic B) exergonic C) anabolic D) allosteric E) nonspontaneous
B
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent? A) electron transport B) glycolysis C) the citric acid cycle D) oxidative phosphorylation E) chemiosmosis
B
Which step shows a split of one molecule into two smaller molecules?
B
Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy? A) The covalent bonds in organic molecules are higher energy bonds than those in water and carbon dioxide. B) Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O). C) The oxidation of organic compounds can be used to make ATP. D) The electrons have a higher potential energy when associated with water and CO2 than they do in organic compounds. E) The covalent bond in O2 is unstable and easily broken by electrons from organic molecules.
B
Why is ATP an important molecule in metabolism? A) Its hydrolysis provides an input of free energy for exergonic reactions. B) It provides energy coupling between exergonic and endergonic reactions. C) Its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy. D) Its terminal phosphate bond has higher energy than the other two. E) A, B, C, and D
B
Why is glycolysis considered to be one of the first metabolic pathways to have evolved? A) It produces much less ATP than does oxidative phosphorylation. B) It is found in the cytosol, does not involve oxygen, and is present in most organisms. C) It is found in prokaryotic cells but not in eukaryotic cells. D) It relies on chemiosmosis which is a metabolic mechanism present only in the first cells-prokaryotic cells. E) It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells.
B
A number of systems for pumping across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases although they don't often hydrolyze ATP unless they are simultaneously transporting ions. Small increases in calcium ions in the cytosol trigger a number of different intracellular reactions, so the cells must keep the calcium concentration quite low. Muscle cells also transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a muscle cell cytosol has a free calcium ion concentration of 10-7 in a resting cell, while the concentration in the SR can be 10-2, then how is the ATPase acting? A) The ATP must be powering an inflow of calcium from the outside of the cell into the SR. B) ATP must be transferring Pi to the SR to enable this to occur. C) ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient. D) The calcium ions must be diffusing back into the SR along the concentration gradient. E) The route of calcium ions must be from SR to the cytosol, to the cell's environment.
C
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. 62) What is substance X? A) a coenzyme B) an allosteric inhibitor C) a substrate D) an intermediate E) the product
C
A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because A) the starch solution has less free energy than the sugar solution. B) the hydrolysis of starch to sugar is endergonic. C) the activation energy barrier for this reaction cannot be surmounted. D) starch cannot be hydrolyzed in the presence of so much water. E) starch hydrolysis is nonspontaneous.
C
An important group of peripheral membrane proteins are enzymes, such as the phospholipases that attack the head groups of phospholipids leading to the degradation of damaged membranes. What properties must these enzymes exhibit? A) resistance to degradation B) independence from cofactor interaction C) water solubility D) lipid solubility E) membrane spanning domains
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
During oxidative phosphorylation, H2O is formed. Where does the oxygen for the synthesis of the water come from? A) carbon dioxide (CO2) B) glucose (C6H12O6) C) molecular oxygen (O2) D) pyruvate (C3H3O3-) E) lactate (C3H5O3-)
C
Each time a molecule of glucose (C6H12O6) is completely oxidized via aerobic respiration, how many oxygen molecules (O2) are required? A) 1 B) 2 C) 6 D) 12 E) 38
C
How many molecules of carbon dioxide (CO2) would be produced by five turns of the citric acid cycle? A) 2 B) 5 C) 10 D) 12 E) 60
C
How many reduced dinucleotides would be produced with four turns of the citric acid cycle? A) 1 FADH2 and 4 NADH B) 2 FADH2 and 8 NADH C) 4 FADH2 and 12 NADH D) 1 FAD and 4 NAD+ E) 4 FAD+ and 12 NAD+
C
In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer mitochondrial membranes, and about 17 X that of the cell's plasma membrane. What purpose must this serve? A) It allows for increased rate of glycolysis. B) It allows for increased rate of the citric acid cycle. C) It increases the surface for oxidative phosphoryation. D) It increases the surface for substrate-level phosphorylation. E) It allows the liver cell to have fewer mitochondria.
C
In mitochondria, exergonic redox reactions A) are the source of energy driving prokaryotic ATP synthesis. B) are directly coupled to substrate-level phosphorylation. C) provide the energy that establishes the proton gradient. D) reduce carbon atoms to carbon dioxide. E) are coupled via phosphorylated intermediates to endergonic processes.
C
In which reaction does an intermediate pathway become oxidized?
C
In which step is an inorganic phosphate added to the reactant?
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
Most cells cannot harness heat to perform work because A) heat is not a form of energy. B) cells do not have much heat; they are relatively cool. C) temperature is usually uniform throughout a cell. D) heat can never be used to do work. E) heat denatures enzymes.
C
Muscle cells, when an individual is exercising heavily and when the muscle becomes oxygen deprived, convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells? A) It is converted to NAD+. B) It produces CO2 and water. C) It is taken to the liver and converted back to pyruvate. D) It reduces FADH2 to FAD+. E) It is converted to alcohol.
C
One 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
Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy (ΔG = -686 kcal/mol). The phosphorylation of ADP to form ATP stores approximately 7.3 kcal per mole of ATP. What is the approximate efficiency of cellular respiration for a "mutant" organism that produces only 29 moles of ATP for every mole of glucose oxidized, rather than the usual 36-38 moles of ATP? A) 0.4% B) 25% C) 30% D) 40% E) 60%
C
Some bacteria are metabolically active in hot springs because A) they are able to maintain a cooler internal temperature. B) high temperatures make catalysis unnecessary. C) their enzymes have high optimal temperatures. D) their enzymes are completely insensitive to temperature. E) they use molecules other than proteins or RNAs as their main catalysts.
C
Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid. 46) Based on this information, which of the following is correct? A) Succinate dehydrogenase is the enzyme, and fumarate is the substrate. B) Succinate dehydrogenase is the enzyme, and malonic acid is the substrate. C) Succinate is the substrate, and fumarate is the product. D) Fumarate is the product, and malonic acid is a noncompetitive inhibitor. E) Malonic acid is the product, and fumarate is a competitive inhibitor.
C
Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in A) bringing glucose and fructose together to form sucrose. B) the release of water from sucrose as the bond between glucose and fructose is broken. C) breaking the bond between glucose and fructose and forming new bonds from the atoms of water. D) production of water from the sugar as bonds are broken between the glucose monomers. E) utilization of water as a covalent bond is formed between glucose and fructose to form sucrase.
C
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mole and the free energy for the reduction of NAD+ to NADH is +53 kcal/mole. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed? A) Most of the free energy available from the oxidation of glucose is used in the production of ATP in glycolysis. B) Glycolysis is a very inefficient reaction, with much of the energy of glucose released as heat. C) Most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis. D) There is no CO2 or water produced as products of glycolysis. E) Glycolysis consists of many enzymatic reactions, each of which extracts some energy from the glucose molecule.
C
The mathematical expression for the change in free energy of a system is △G =△H-T△S. Which of the following is (are) correct? A) △S is the change in enthalpy, a measure of randomness. B) △H is the change in entropy, the energy available to do work. C) △G is the change in free energy. D) T is the temperature in degrees Celsius.
C
What happens at the end of the chain? A) The 2 original electrons combine with NAD+. B) The 2 original electrons combine with oxygen. C) 4 electrons combine with oxygen and protons. D) 4 electrons combine with hydrogen and oxygen atoms. E) 1 electron combines with oxygen and hydrogen.
C
What term is used to describe the transfer of free energy from catabolic pathways to anabolic pathways? A) feedback regulation B) bioenergetics C) energy coupling D) entropy E) cooperativity
C
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes A) dehydrogenated. B) hydrogenated. C) oxidized. D) reduced. E) an oxidizing agent.
C
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a hydrogen ion) the molecule becomes A) hydrogenated. B) oxidized. C) reduced. D) redoxed. E) a reducing agent.
C
When you have a severe fever, what may be a grave consequence if this is not controlled? A) destruction of your enzymes' primary structure B) removal of amine groups from your proteins C) change in the folding of enzymes D) removal of the amino acids in active sites E) binding of enzymes to inappropriate substrates
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
Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle? A) pyruvate B) malate or fumarate C) acetyl CoA D) α-ketoglutarate E) succinyl CoA
C
Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher? A) curve 1 B) curve 2 C) curve 3 D) curve 4 E) curve 5
C
Which kind of metabolic poison would most directly interfere with glycolysis? A) an agent that reacts with oxygen and depletes its concentration in the cell B) an agent that binds to pyruvate and inactivates it C) an agent that closely mimics the structure of glucose but is not metabolized D) an agent that reacts with NADH and oxidizes it to NAD+ E) an agent that blocks the passage of electrons along the electron transport chain
C
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule? A) the citric acid cycle B) the electron transport chain C) glycolysis D) synthesis of acetyl CoA from pyruvate E) reduction of pyruvate to lactate
C
Which of the following is (are) true for anabolic pathways? A) They do not depend on enzymes. B) They are usually highly spontaneous chemical reactions. C) They consume energy to build up polymers from monomers. D) They release energy as they degrade polymers to monomers.
C
Which of the following is an example of cooperativity? A) the binding of an end product of a metabolic pathway to the first enzyme that acts in the pathway B) protein function at one site affected by binding at another of its active sites C) a molecule binding at one unit of a tetramer allowing faster binding at each of the other three D) the effect of increasing temperature on the rate of an enzymatic reaction E) binding of an ATP molecule along with one of the substrate molecules in an active site
C
Which of the following is most similar in structure to ATP? A) an anabolic steroid B) a DNA helix C) an RNA nucleotide D) an amino acid with three phosphate groups attached E) a phospholipid
C
Which of the following represents the activation energy required for a noncatalyzed reaction? A) a B) b C) c D) d E) e
C
Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein? A) +△H, +△S, +△G B) +△H, -△S, -△G C) +△H, -△S, +△G D) -△H, -△S, +△G E) -△H, +△S, +△G
C
Which of the following statements describes enzyme cooperativity? A) A multi-enzyme complex contains all the enzymes of a metabolic pathway. B) A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway. C) A substrate molecule bound to an active site affects the active site of several subunits. D) Several substrate molecules can be catalyzed by the same enzyme. E) A substrate binds to an active site and inhibits cooperation between enzymes in a pathway.
C
Why is coenzyme A, a sulfur containing molecule derived from a B vitamin, added? A) because sulfur is needed for the molecule to enter the mitochondrion B) in order to utilize this portion of a B vitamin which would otherwise be a waste product from another pathway C) to provide a relatively unstable molecule whose acetyl portion can readily bind to oxaloacetate D) because it drives the reaction that regenerates NAD+ E) in order to remove one molecule of CO2
C
A molecule that is phosphorylated A) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate. B) has a decreased chemical reactivity; it is less likely to provide energy for cellular work. C) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate. D) has an increased chemical reactivity; it is primed to do cellular work. E) has less energy than before its phosphorylation and therefore less energy for cellular work.
D
According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? A) The binding of the substrate depends on the shape of the active site. B) Some enzymes change their structure when activators bind to the enzyme. C) A competitive inhibitor can outcompete the substrate for the active site. D) The binding of the substrate changes the shape of the enzyme's active site. E) The active site creates a microenvironment ideal for the reaction.
D
After the second agitation of the membrane vesicles, what must be lost from the membrane? A) the ability of NADH to transfer electrons to the first acceptor in the electron transport chain B) the prosthetic groups like heme from the transport system C) cytochromes D) ATP synthase, in whole or in part E) the contact required between inner and outer membrane surfaces
D
Assume that the reaction has a △G of -5.6 kcal/mol. Which of the following would be true? A) The reaction could be coupled to power an endergonic reaction with a △G of +6.2 kcal/mol. B) The reaction could be coupled to power an exergonic reaction with a △G of +8.8 kcal/mol. C) The reaction would result in a decrease in entropy (S) and an increase in the total energy content (H) of the system. D) The reaction would result in an increase in entropy (S) and a decrease in the total energy content (H) of the system. E) The reaction would result in products (C + D) with a greater free-energy content than in the initial reactants (A + B).
D
Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle. Which intermediate would supply the carbon skeleton for synthesis of a five-carbon amino acid? A) succinate B) malate C) citrate D) α-ketoglutarate E) isocitrate
D
Cells do not catabolize carbon dioxide because A) its double bonds are too stable to be broken. B) CO2 has fewer bonding electrons than other organic compounds. C) CO2 is already completely reduced. D) CO2 is already completely oxidized. E) the molecule has too few atoms.
D
Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell? A) a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium B) a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings C) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment D) a chemical reaction in which both the reactants and products are only used in a metabolic pathway that is completely inactive E) There is no possibility of having chemical equilibrium in any living cell.
D
Energy released by the electron transport chain is used to pump H+ ions into which location? A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix
D
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur? A) in photosynthetic cells in the light, while photosynthesis occurs concurrently B) in non-photosynthesizing cells only C) in cells that are storing glucose only D) in photosynthesizing cells in dark periods and in other tissues all the time E) in photosynthesizing cells in the light and in other tissues in the dark
D
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
In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + Pi to ATP? A) energy released as electrons flow through the electron transport system B) energy released from substrate-level phosphorylation C) energy released from ATP synthase pumping hydrogen ions from the mitochondrial matrix D) energy released from movement of protons through ATP synthase E) No external source of energy is required because the reaction is exergonic.
D
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics? A) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time. B) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is balanced by an increase in the entropy of the universe. C) Living organisms do not follow the laws of thermodynamics. D) As a consequence of growing, organisms create more disorder in their environment than the decrease in entropy associated with their growth. E) Living organisms are able to transform energy into entropy.
D
Some enzymatic regulation is allosteric. In such cases, which of the following would usually be found? A) cooperativity B) feedback inhibition C) both activating and inhibitory activity D) an enzyme with more than one subunit E) the need for cofactors
D
Starting with citrate, which of the following combinations of products would result from three turns of the citric acid cycle? A) 1 ATP, 2 CO2, 3 NADH, and 1 FADH2 B) 2 ATP, 2 CO2, 1 NADH, and 3 FADH2 C) 3 ATP, 3 CO2, 3 NADH, and 3 FADH2 D) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2 E) 38 ATP, 6 CO2, 3 NADH, and 12 FADH2
D
The accompanying figure shows the electron transport chain. Which of the following is the combination of substances that is initially added to the chain? A) oxygen, carbon dioxide, and water B) NAD+ , FAD, and electrons C) NADH, FADH2, and protons D) NADH, FADH2, and electrons E) Oxygen and electrons
D
The 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 immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is A) the oxidation of glucose and other organic compounds. B) the flow of electrons down the electron transport chain. C) the affinity of oxygen for electrons. D) the H+ concentration gradient across the inner mitochondrial membrane. E) the transfer of phosphate to ADP.
D
These three steps result in the formation of A) acetyl CoA, O2, and ATP. B) acetyl CoA, FADH2, and CO2. C) acetyl CoA, FAD, H2, and CO2. D) acetyl CoA, NADH, H+, and CO2. E) acetyl CoA, NAD+, ATP, and CO2.
D
When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell? A) It is released as an excretory waste. B) It can only be used to regenerate more ATP. C) It can be added to water and excreted as a liquid. D) It can be added to other molecules in order to activate them. E) It can enter the nucleus to affect gene expression.
D
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated? A) It is used to power yet more cellular work. B) It is used to store energy as more ATP. C) It is used to generate ADP from nucleotide precursors. D) It is lost to the environment. E) It is transported to specific organs such as the brain.
D
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the A) formation of ATP. B) reduction of NAD+. C) restoration of the Na+/K+ balance across the membrane. D) creation of a proton gradient. E) lowering of pH in the mitochondrial matrix.
D
When muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by A) buildup of pyruvate. B) buildup of lactate. C) increase in sodium ions. D) increase in potassium ions. E) increase in ethanol.
D
Whenever energy is transformed, there is always an increase in the A) free energy of the system. B) free energy of the universe. C) entropy of the system. D) entropy of the universe. E) enthalpy of the universe.
D
Which best describes the reaction? A) The amount of free energy initially present in the reactants is indicated by "a." B) The amount of free energy present in the products is indicated by "e." C) The amount of free energy released as a result of the noncatalyzed reaction is indicated by "c." D) The amount of free energy released as a result of the catalyzed reaction is indicated by "d." E) The difference between "b" and "c" is the activation energy added by the presence of the enzyme.
D
Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid? A) curve 1 B) curve 2 C) curve 3 D) curve 4 E) curve 5
D
Which metabolic pathway is common to both cellular respiration and fermentation? A) the oxidation of pyruvate to acetyl CoA B) the citric acid cycle C) oxidative phosphorylation D) glycolysis E) chemiosmosis
D
Which of the following describes the sequence of electron carriers in the electron transport chain, starting with the least electronegative? A) ubiquinone (Q), cytochromes (Cyt), FMN, Fe•S B) cytochromes (Cyt), FMN, ubiquinone, Fe•S C) Fe•S, FMN, cytochromes (Cyt), ubiquinone D) FMN, Fe•S, ubiquinone, cytochromes (Cyt) E) cytochromes (Cyt), Fe•S, ubiquinone, FMN
D
Which of the following is an example of potential rather than kinetic energy? A) a boy mowing grass B) water rushing over Niagara Falls C) a firefly using light flashes to attract a mate D) a food molecule made up of energy-rich macromolecules E) an insect foraging for food
D
Which of the following is the most correct interpretation of the figure? A) Inorganic phosphate is created from organic phosphate. B) Energy from catabolism can be used directly for performing cellular work. C) ADP + Pi are a set of molecules that store energy for catabolism. D) ATP is a molecule that acts as an intermediary to store energy for cellular work. E) Pi acts as a shuttle molecule to move energy from ATP to ADP.
D
Which of the following is true of enzymes? A) Enzymes may require a nonprotein cofactor or ion for catalysis to take speed up more appreciably than if the enzymes act alone. B) Enzyme function is increased if the three-dimensional structure or conformation of an enzyme is altered. C) Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. D) Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
D
Which of the following is true of metabolism in its entirety? A) Metabolism depends on a constant supply of energy from food B) Metabolism depends on an organism's adequate hydration C) Metabolism utilizes all of an organism's resources D) Metabolism is a property of organismal life E) Metabolism manages the increase of entropy in an organism
D
Which of the following represents the difference between the free-energy content of the reaction and the free-energy content of the products? A) a B) b C) c D) d E) e
D
Which of the following statements is a logical consequence of the second law of thermodynamics? A) If the entropy of a system increases, there must be a corresponding decrease in the entropy of the universe. B) If there is an increase in the energy of a system, there must be a corresponding decrease in the energy of the rest of the universe. C) Every energy transfer requires activation energy from the environment. D) Every chemical reaction must increase the total entropy of the universe. E) Energy can be transferred or transformed, but it cannot be created or destroyed.
D
Which of the following statements is representative of the second law of thermodynamics? A) Conversion of energy from one form to another is always accompanied by some gain of free energy. B) Heat represents a form of energy that can be used by most organisms to do work. C) Without an input of energy, organisms would tend toward decreasing 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.
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
D
Why are carbohydrates and fats considered high energy foods? A) They have a lot of oxygen atoms. B) They have no nitrogen in their makeup. C) They can have very long carbon skeletons. D) They have a lot of electrons associated with hydrogen. E) They are easily reduced.
D
Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n) A) competitive inhibitor of the enzyme. B) noncompetitive inhibitor of the enzyme. C) allosteric activator of the enzyme. D) cofactor necessary for enzyme activity. E) coenzyme derived from a vitamin.
D
C. B. Van Niel's experiments with purple sulfur bacteria led to which of the following hypotheses?
During plant photosynthesis, the oxygen gas that is released comes from water.
Why are summer leaves green, even though carotenoids are present?
During summer, chlorophyll is more abundant than carotenoids in leaves.
An organism is discovered that consumes a considerable amount of sugar, yet does not gain much weight when denied air. Curiously, the consumption of sugar increases as air is removed from the organism's environment, but the organism seems to thrive even in the absence of air. When returned to normal air, the organism does fine. Which of the following best describes the organism? A) It must use a molecule other than oxygen to accept electrons from the electron transport chain. B) It is a normal eukaryotic organism. C) The organism obviously lacks the citric acid cycle and electron transport chain. D) It is an anaerobic organism. E) It is a facultative anaerobe.
E
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in cellular respiration? A) 2 B) 4 C) 15 D) 38 E) 76
E
Approximately what percentage of the energy of glucose (C6H12O6) is transferred to storage in ATP as a result of the complete oxidation of glucose to CO2 and water in cellular respiration? A) 2% B) 4% C) 10% D) 25% E) 40%
E
During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level? A) NAD+ B) NADH C) ATP D) ADP + Pi E) FADH2
E
During cellular respiration, acetyl CoA accumulates in which location? A) cytosol B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) mitochondrial matrix
E
For each molecule of glucose that is metabolized by glycolysis and the citric acid cycle, what is the total number of NADH + FADH2 molecules produced? A) 4 B) 5 C) 6 D) 10 E) 12
E
If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur? A) Additional product would be formed. B) Additional substrate would be formed. C) The reaction would change from endergonic to exergonic. D) The free energy of the system would change. E) Nothing; the reaction would stay at equilibrium.
E
In coupled reactions, in which direction would the endergonic reaction be driven relative to the clockwise direction of the ATP reaction above and shown in the figure? A) from left to right at the top of the figure B) under the symbol for energy doing cellular work in the figure C) from right to left at the bottom of the figure D) it would be shown separately after the figure E) it would be shown in a clockwise direction at the top of the figure
E
In vertebrate animals, brown fat tissue's color is due to abundant mitochondria. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few mitochondria. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue? A) to increase the rate of oxidative phosphorylation from its few mitochondria B) to allow the animals to regulate their metabolic rate when it is especially hot C) to increase the production of ATP synthase D) to allow other membranes of the cell to perform mitochondrial function E) to regulate temperature by converting energy from NADH oxidation to heat
E
Inside an active mitochondrion, most electrons follow which pathway? A) glycolysis → NADH → oxidative phosphorylation → ATP → oxygen B) citric acid cycle → FADH2 → electron transport chain → ATP C) electron transport chain → citric acid cycle → ATP → oxygen D) pyruvate → citric acid cycle → ATP → NADH → oxygen E) citric acid cycle → NADH → electron transport chain → oxygen
E
It should be possible to reconstitute the abilities of the vesicles if which of the following is added? A) cytochromes B) extra NADH C) a second membrane surface D) more electrons E) intact ATP synthase
E
Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which of the following statements describes a function of phosphofructokinase? A) It is activated by AMP (derived from ADP). B) It is activated by ATP. C) It is inhibited by citrate, an intermediate of the citric acid cycle. D) It catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, an early step of glycolysis. E) It is an allosteric enzyme.
E
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed during glycolysis? A) 0% B) 2% C) 10% D) 38% E) 100%
E
The parts of the figure labeled with Roman numerals symbolize what concept? A) different inner mitochondrial membranes B) different mitochondria functioning together C) molecules with different attached metal ions D) carbohydrate framework holding the molecules in place E) multimeric groups of proteins in 4 complexes
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 purpose of beta oxidation in respiration? A) oxidation of glucose B) oxidation of pyruvate C) feedback regulation D) control of ATP accumulation E) breakdown of fatty acids
E
What must be the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in DNA and RNA? A) The sugar molecule is different. B) The nitrogen-containing base is different. C) The number of phosphates is three instead of one. D) The number of phosphates is three instead of two. E) There is no difference.
E
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) Reactant and product concentrations are not the same
E
When electrons move closer to a more electronegative atom, what happens? A) Energy is released. B) Energy is consumed. C) The more electronegative atom is reduced. D) The more electronegative atom is oxidized. E) A and C are correct.
E
Where does glycolysis takes place? A) mitochondrial matrix B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) cytosol
E
Which curve was most likely generated from an enzyme that requires a cofactor? A) curve 1 B) curve 2 C) curve 4 D) curve 5 E) It is not possible to determine whether an enzyme requires a cofactor from these data.
E
Which of the following couples chemiosmosis to energy storage? A) NADH B) FADH2 C) cytochromes D) electron transport E) ATP synthase
E
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water? A) glycolysis B) fermentation C) oxidation of pyruvate to acetyl CoA D) citric acid cycle E) oxidative phosphorylation (chemiosmosis)
E
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A) catalysis B) metabolism C) anabolism D) dehydration E) catabolism
E
Why is glycolysis described as having an investment phase and a payoff phase? A) It both splits molecules and assembles molecules. B) It attaches and detaches phosphate groups. C) It uses glucose and generates pyruvate. D) It shifts molecules from cytosol to mitochondrion. E) It uses stored ATP and then forms a net increase in ATP.
E
In the diagram, which molecule is best represented by the letter A?
Ferredoxin
In the diagram of a chloroplast, which structure is best represented by the letter D?
Granum
In the diagram of a chloroplast, which structure is best represented by the letter B?
Inner membrane
Why is the chemical reduction of an electron acceptor in the photosynthetic reaction center important to plant function?
It allows the energy of absorbed light to be trapped and converted to chemical energy.
Why is it critical for plants to maintain a high concentration of carbon dioxide in the leaves?
It helps prevent photorespiration.
What is the source of atmospheric oxygen released during photosynthesis?
It is produced via splitting of the water molecules during the light-capturing reactions.
Why is pheophytin an important component of photosystem II?
It transforms light energy by acting as the initial electron acceptor.
During photosynthesis, which of the following reactions occur?
Light energy is used to raise the potential energy of electrons.
Isolated thylakoids were incubated in an acidic solution at pH 4 until the pH was equilibrated across the thylakoid membrane. The thylakoids were then transferred to a buffer at pH 8 with ADP and inorganic phosphate. ATP was synthesized. Did this experiment require light to generate the ATP?
No, because ATP synthesis depends only on the presence of a hydrogen ion gradient and does not require light directly.
In the diagram of a chloroplast, which structure is best represented by the letter A?
Outer membrane
In the diagram, which molecule is best represented by the letter D?
Plastocyanin (PC)
In the diagram of a chloroplast, which structure is best represented by the letter E?
Stroma
What is the evidence for the existence of two photosystems?
The combination of light at 680 nm and 700 nm is much more effective in stimulating photosynthesis than is either wavelength alone.
Predict the color of a pigment that absorbs light of only green, yellow, and red wavelengths.
The pigment will appear blue.
How are the light-capturing reactions and CO2-reduction reactions of photosynthesis related?
The products of light-capturing reactions are used in CO2-reduction reactions.
Chlorophyll consists of a magnesium-containing head and a long, hydrophobic hydrocarbon tail. Why is the tail region important to the molecule's function?
The tail region anchors chlorophyll in the thylakoid membrane.
The Calvin cycle uses six ATP molecules to produce one three-carbon sugar (glyceraldehyde-3-phosphate, G3P) from three molecules of RuBP and three molecules of carbon dioxide. Yet the Calvin cycle actually requires nine ATP molecules to function. Why?
Three additional ATP molecules are used to regenerate RuBP.
In the diagram of a chloroplast, which structure is best represented by the letter C?
Thylakoids
In green plants, the primary function of the Calvin cycle is to
construct simple sugars from carbon dioxide
Electrons excited by the absorption of light in photosystem I are transferred to iron-sulfur electron acceptors and, therefore, must be replaced. The replacement electrons come directly from
plastocyanin
In the diagram, which molecule is best represented by the letter B?
plastoquinone (PQ)
The primary biochemical outcome of the activity of photosystem I is to
reduce NADP+
The enzyme needed to begin the Calvin cycle in C3 plants is
rubisco
Rubisco differs from PEP carboxylase in that
rubisco can use oxygen gas as a substrate
The Z scheme is
the characteristic path of electrons from photosystem II to photosystem I.
Electrons excited by absorption of light in photosystem II are transferred to plastoquinone via pheophytin, and, therefore, must be replaced. The replacement electrons come from
water