Key Concepts:
• Catabolic pathways yield energy by oxidizing organic fuels.
• Glycolysis harvests chemical energy by oxidizing glucose to pyruvate.
• After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules.
• During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis.
• Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen.
• Glycolysis and the citric acid cycle connect to many other metabolic pathways.
Terms : Hide Images
| 1783891553 | Acetyl CoA | acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme | 0 | |
| 1783891554 | Alcohol Fermentation | glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide | 1 | |
| 1785838549 | ATP Synthase | a complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP; ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes | 2 | |
| 1785838550 | Bar Graph | a graph in which the independent variable represents groups or nonnumerical categories and the values of the dependent variable(s) are shown by bars | 3 | |
| 1785838551 | Beta Oxidation | a metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA | 4 | |
| 1785838552 | Cellular Respiration | the catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP | 5 | |
| 1785838553 | Chemiosmosis | an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP; under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis | 6 | |
| 1785838554 | Citric Acid Cycle | a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration | 7 | |
| 1785838555 | Cytochrome | an iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells | 8 | |
| 1785838556 | Electron Transport Chain | a sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP | 9 | |
| 1785838557 | Facultative Anaerobe | an organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present | 10 | |
| 1785838558 | Fermentation | a catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid | 11 | |
| 1785838559 | Glycolysis | a series of reactions that ultimately splits glucose into pyruvate; glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration | 12 | |
| 1785838560 | Lactic Acid Fermentation | glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide | 13 | |
| 1785838561 | Medulla Oblongata | the lowest part of the vertebrate brain, commonly called the medulla; a swelling of the hindbrain anterior to the spinal cord that controls autonomic, homeostatic functions, including breathing, heart and blood vessel activity, swallowing, digestion, and vomiting | 14 | |
| 1785838562 | NAD+ | nicotinamide adenine dinucleotide, a coenzyme that cycles easily between oxidized (NAD+) and reduced (NADH) states, thus acting as an electron carrier | 15 | |
| 1785838563 | Obligate Anaerobe | an organism that carries out only fermentation or anaerobic respiration; such organisms cannot use oxygen and in fact may be poisoned by it | 16 | |
| 1785838564 | Oxidation | the complete or partial loss of electrons from a substance involved in a redox reaction | 17 | |
| 1785838565 | Oxidative Phosphorylation | the production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration | 18 | |
| 1785838566 | Oxidizing Agent | the electron acceptor in a redox reaction | 19 | |
| 1785838567 | Proton-Motive Force | the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H+) across a biological membrane during chemiosmosis | 20 | |
| 1785838568 | Redox Reaction | a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another; short for reduction-oxidation reaction | 21 | |
| 1785838569 | Reducing Agent | the electron donor in a redox reaction | 22 | |
| 1785838570 | Reduction | the complete or partial addition of electrons to a substance involved in a redox reaction | 23 | |
| 1785838571 | Substrate-Level Phosphorylation | the enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism | 24 | |
| 1801586846 | A molecule becomes more oxidized when it __________. a. gains a hydrogen (H+) ion b. changes shape c. loses a hydrogen (H+) ion d. loses an electron e. gains an electron | loses an electron During oxidation, an electron is removed. | 25 | |
| 1801586847 | In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced. a. glucose ... ATP b. oxygen ... ATP c. glucose ... oxygen d. carbon dioxide ... water e. ATP ... oxygen | glucose ... oxygen In cellular respiration, electrons and hydrogen are removed from glucose and added to oxygen. | 26 | |
| 1801586848 | Most of the ATP produced in cellular respiration comes from which of the following processes? a. reduction of NADH b. substrate-level phosphorylation c. glycolysis d. the citric acid cycle e. oxidative phosphorylation | oxidative phosphorylation After hydrogen ions are pumped into the mitochondrial intermembrane space, they flow back through ATP synthase, which produces most of the ATP associated with cellular respiration. | 27 | |
| 1801586849 | Which of the following is a correct description of the events of cellular respiration in proper sequence? a. glycolysis; oxidative phosphorylation; citric acid cycle; oxidation of pyruvate b. oxidation of glucose to pyruvate; reduction of pyruvate; citric acid cycle; oxidative phosphorylation c. oxidation of pyruvate; citric acid cycle; oxidation of glucose to pyruvate; oxidative phosphorylation d. glycolysis; reduction of pyruvate; citric acid cycle; oxidative phosphorylation e. oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation | oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation This is the correct sequence of events in cellular respiration. | 28 | |
| 1801586850 | Oxygen gas (O2) is one of the strongest oxidizing agents known. The explanation for this is that __________. a. the oxygen atom is very electronegative b. oxygen is so abundant in the atmosphere c. oxygen gas contains a double bond d. oxygen gas is composed of two atoms of oxygen e. oxygen acts as the final electron acceptor in cellular respiration | the oxygen atom is very electronegative The high electronegativity of the oxygen atom is the reason that oxygen is such a strong oxidizing agent. | 29 | |
| 1801586851 | The function of cellular respiration is to __________. a. reduce CO2 b. extract CO2 from the atmosphere c. produce carbohydrates d. extract usable energy from glucose e. synthesize macromolecules from monomers | extract usable energy from glucose The most efficient pathway for ATP generation is cellular respiration, in which oxygen is consumed as a reactant, along with the organic fuel (frequently glucose). | 30 | |
| 1801586852 | During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction? a. carbon dioxide b. glucose c. water d. oxygen e. both glucose and carbon dioxide | oxygen In cellular respiration, glucose is oxidized (resulting in the production of carbon dioxide) and oxygen is reduced (resulting in the production of water). | 31 | |
| 1801586853 | Which of the following statements is the best explanation of what happens to the temperature and carbon dioxide concentration during a 1-hour class period in a classroom of 300 students if the heating and air conditioning is turned off and all doors are kept closed? a. Temperature goes up and the level of carbon dioxide goes down. This is because cellular respiration is an exergonic process that is only about 38% efficient; the remaining energy is lost to the environment as heat. Also, carbon dioxide is being converted to organic molecules such as fats and sugars during cellular respiration. b. Temperature goes down and carbon dioxide levels remain constant. This is because cellular respiration, being an endergonic reaction, requires an input of heat energy from the environment to occur and because carbon dioxide is neither produced nor consumed by cellular respiration. c. Neither temperature nor carbon dioxide levels change because cellular respiration is 100% efficient and because carbon dioxide produced by cellular respiration is just as rapidly consumed by cellular respiration. d. Temperature goes up but carbon dioxide levels remain constant because heat is a by-product of cellular respiration but carbon dioxide is converted to sugar during cellular respiration. e. Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration. | Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration. The oxidation of organic molecules produces carbon dioxide, and as the exergonic process of cellular respiration is not 100% efficient, some energy is lost to the environment as heat. | 32 | |
| 1801586854 | A small amount of ATP is made in glycolysis by which of the following processes? a. attachment of a free inorganic phosphate (Pi) group to ADP to make ATP b. transfer of electrons and hydrogen atoms to NAD+ c. transport of electrons through a series of carriers d. transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation e. harnessing energy from the sun | transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation Remember that glucose is phosphorylated at the beginning of glycolysis. | 33 | |
| 1801586855 | Where do the reactions of glycolysis occur in a eukaryotic cell? a. across the inner membrane of the mitochondrion b. the matrix of the mitochondrion c. the inner membrane of the mitochondrion d. in the intermembrane space of the mitochondrion e. the cytosol | the cytosol Glycolysis occurs in the cytosol. | 34 | |
| 1801586856 | Which of the following is the process in which glucose is oxidized to generate two molecules of pyruvate, and in which ATP and NADH are produced? a. the citric acid cycle b. chemiosmosis c. the oxidation of pyruvate d. fermentation e. None of the listed responses is correct. | None of the listed responses is correct. The name of the process that oxidizes glucose to pyruvate and produces ATP and NADH is glycolysis. | 35 | |
| 1801586857 | A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to kill bacteria in people with infections. However, he cannot do this because __________. a. human cells must also perform glycolysis; the drug might also poison them b. glycolysis produces so little ATP that the drug will have little effect c. this step in the pathway of glycolysis can be skipped in bacteria, but not in humans d. glycolysis can occur without the action of enzymes e. bacteria are prokaryotes; they usually do not need to perform glycolysis | human cells must also perform glycolysis; the drug might also poison them The chemist's drug could have a devastating effect on human cells. | 36 | |
| 1801586858 | There is no production of carbon dioxide in glycolysis. Which of the following is the best explanation for this fact? a. There is very little ATP produced in glycolysis. b. The products of glycolysis contain the same total number of carbon atoms as in the starting material. c. Glucose contains more carbons than the number of carbons found in the pyruvate products that are produced by glycolysis. d. There are no oxidation or reduction reactions in glycolysis to produce CO2. e. The initial steps of glycolysis require an input of energy in the form of ATP (two per glucose). | he products of glycolysis contain the same total number of carbon atoms as in the starting material. All of the carbon in one glucose molecule is accounted for in the two molecules of pyruvate produced by glycolysis. | 37 | |
| 1801586859 | Which of the following molecules in the process of glycolysis possesses the most chemical energy? a. fructose-6-phosphate b. glyceraldehyde-3-phosphate c. glucose d. pyruvate e. fructose-1,6-bisphosphate | fructose-1,6-bisphosphate Fructose-1,6-bisphosphate has received two phosphate groups from ATP, conserving some of the energy derived from the hydrolysis of ATP in the fructose-1,6-bisphosphate molecule. | 38 | |
| 1801586860 | Which of the following processes generates most of the NADH that delivers electrons to the electron transport chain? a. substrate-level phosphorylation b. the citric acid cycle c. glycolysis d. oxidative phosphorylation e. anabolic pathways | the citric acid cycle Most of the NADH is produced during the citric acid cycle, along with some FADH2. | 39 | |
| 1801586861 | In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in __________. a. ATP b. water c. NADH d. carbon dioxide e. oxygen gas | carbon dioxide One molecule of CO2 is formed when pyruvate is converted to acetyl CoA, and two molecules of CO2 are produced in the citric acid cycle. | 40 | |
| 1801586862 | In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs? a. Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH. b. Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are donated to NADH to produce NAD+. c. Pyruvate is reduced to acetyl-coA, which involves the reduction of pyruvate, the addition of a carbon dioxide from the environment, and its reduction by NADH. d. Pyruvate is reduced and a molecule of carbon dioxide is removed. The electrons removed in this process are used to oxidize NAD+ to NADH. e. Pyruvate is ionized directly to acetyl-coA. | Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH. In addition to these events, a molecule of coenzyme A is attached to the resulting acetyl group. | 41 | |
| 1801586863 | Why is the citric acid cycle called a "cycle"? a. NADH is cycled down the electron transport chain. b. The acetyl CoA that enters the cycle is regenerated in the last step of the pathway. c. All of the carbon from glucose is cycled back into the atmosphere as carbon dioxide. d. NAD+ and FAD are recycled. e. The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle. | The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle. The cycling referred to is that of the resynthesis of the four-carbon compound. | 42 | |
| 1801586864 | In the citric acid cycle, for each pyruvate that enters the cycle, one ATP, three NADH, and one FADH2 are produced. For each glucose molecule that enters glycolysis, how many ATP, NADH, and FADH2 are produced in the citric acid cycle? a. two ATP, six NADH, two FADH2 b. one ATP, three NADH, one FADH2 c. three ATP, three NADH, one FADH2 d. about 38 ATP e. four ATP, six NADH, two FADH2 | two ATP, six NADH, two FADH2 Then the NADH and FADH2 go through the electron transport chain. | 43 | |
| 1801586865 | Where do the reactions of the citric acid cycle occur in eukaryotic cells? a. across the inner membrane of the mitochondrion b. the cytosol c. the cristae of the mitochondrion d. the intermembrane space of the mitochondrion e. the matrix of the mitochondrion | the matrix of the mitochondrion The citric acid cycle, which takes place in the mitochondrial matrix, completes the degradation of glucose. | 44 | |
| 1801586866 | How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen? a. 2 b. 3 c. 4 d. about 16 ATP e. about 32 ATP | 4 There is a net gain of two ATP from glycolysis and one from each molecule of acetyl CoA oxidized in the citric acid cycle for a total of four per glucose. | 45 | |
| 1801586867 | Which of the following represents the major (but not the only) energy accomplishment of the citric acid cycle? a. utilization of O2 b. completion of substrate-level phosphorylation c. formation of ATP d. formation of CO2 e. formation of NADH and FADH2 | formation of NADH and FADH2 Each turn of the citric acid cycle releases carbon dioxide, forms one ATP by oxidative phosphorylation, and passes electrons to three NAD+ and one FAD. | 46 | |
| 1801586868 | After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________. a. CO2 b. ATP c. acetyl CoA d. FADH2 e. NADH | NADH The citric acid cycle produces three NADH per turn of the cycle. | 47 | |
| 1801586869 | Which of the following events accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle? a. release of CO2 and release of coenzyme A b. regeneration of NAD+ c. removal of coenzyme A d. formation of CO2 and synthesis of ATP e. release of CO2 and synthesis of NADH | release of CO2 and synthesis of NADH The carboxyl group of pyruvate is removed as a carbon dioxide molecule. The remaining two-carbon fragment is oxidized to acetate and NAD+ is reduced to NADH. | 48 | |
| 1801586870 | The energy given up by electrons as they move through the electron transport chain is used in which of the following processes? a. the oxidation of water b. the production of CO2 c. pumping H+ across a membrane d. the production of NADH and FADH2 e. the breakdown of glucose | pumping H+ across a membrane Many of the electron transport molecules in the mitochondrion pump a hydrogen ion into the intermembrane space when they pass an electron along the chain. | 49 | |
| 1801586871 | Energy for synthesizing ATP is obtained by ATP synthase directly from which of the following processes? a. the reduction of oxygen b. the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme c. the movement of electrons through a series of carriers d. the oxidation of NADH and FADH2 e. the oxidation of glucose | the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme Hydrogen ions flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production. | 50 | |
| 1801586872 | When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working. Which of the following is the best explanation for this? a. Electrons are no longer available from the electron transport chain to power glycolysis and the citric acid cycle. b. A high level of NADH is present in the cell. c. NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue. d. They run out of ADP. e. The uptake of oxygen stops because electron transport was inhibited. | NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue. Unless the electron transport molecules (NADH and FADH2) can recycle back to their oxidized states (NAD+ and FAD), they will be unable to receive electrons in the other steps of cellular respiration. | 51 | |
| 1801586873 | Most of the electrons removed from glucose by cellular respiration are used for which of the following processes? a. reducing NAD+ to NADH in glycolysis and the citric acid cycle b. producing a proton gradient for ATP synthesis in the mitochondria c. driving substrate-level phosphorylation in glycolysis d. The first two choices are correct. e. The second and third answers are correct. | The first two choices are correct. Electrons from oxidation of glucose are used to reduce NAD+ and produce a proton gradient for ATP synthesis in the mitochondria. | 52 | |
| 1801586874 | Each ATP molecule contains about 1% of the amount of chemical energy available from the complete oxidation of a single glucose molecule. Cellular respiration produces about 32 ATP from one glucose molecule. What happens to the rest of the energy in glucose? a. It is used to make water from hydrogen ions and oxygen. b. It is converted to heat. c. It is released as carbon dioxide and water d. It is stored as fat. e. It is converted to starch. | It is converted to heat. The process is only about 38% efficient, with the rest of the energy lost as heat. | 53 | |
| 1801586875 | During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes? a. at the end of the citric acid cycle to regenerate citric acid b. at the end of glycolysis to oxidize pyruvate c. as a source of O2 in every reaction that produces CO2 d. at the end of the electron transport chain to accept electrons and form H2O e. between glycolysis and the citric acid cycle to split a carbon from pyruvate, producing CO2 | at the end of the electron transport chain to accept electrons and form H2O O2 is the final electron acceptor. | 54 | |
| 1801586876 | Which of the following substances is/are involved in oxidative phosphorylation? a. ATP b. oxygen c. ADP d. None of the listed responses is correct. e. The first three listed substances are involved in oxidative phosphorylation. | The first three listed substances are involved in oxidative phosphorylation. ADP is converted to ATP during oxidative phosphorylation, and oxygen functions as the terminal electron acceptor in oxidative phosphorylation. | 55 | |
| 1801586877 | Which of the following best describes the electron transport chain? a. Acetyl CoA is fully oxidized to CO2. b. Electrons are pumped across a membrane by active transport. c. Glucose is broken down to a three-carbon compound in preparation for the citric acid cycle. d. Electrons are passed from one carrier to another, releasing a little energy at each step. e. Hydrogen atoms are added to CO2 to make an energy-rich compound. | Electrons are passed from one carrier to another, releasing a little energy at each step. NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step. | 56 | |
| 1801586878 | f a compound that allows protons to freely diffuse across membranes is added to cells that are actively metabolizing glucose via cellular respiration, which of the following processes would stop? a. ATP synthesis b. glycolysis c. electron transport d. All of the listed responses are correct. e. None of the listed responses is correct. | None of the listed responses is correct. The chemiosmotic synthesis of ATP would stop in the mitochondria, but substrate-level phosphorylation could continue. | 57 | |
| 1801586879 | Which of the following is the source of the energy that produces the chemiosmotic gradient in mitochondria? a. the production of NADH b. an ATP-dependent proton pump c. ATP d. movement of electrons down the electron transport chain e. the components of the electron transport chain | movement of electrons down the electron transport chain Energy from the flow of electrons along the electron transport chain is used to pump hydrogen ions (protons) across the inner mitochondrial membrane, creating the chemiosmotic gradient. | 58 | |
| 1801586880 | In eukaryotic cells, the components of the electron transport chain are located in or on __________. a. the inner membrane of the mitochondrion b. the matrix of the mitochondrion c. the cytosol d. the intermembrane space of the mitochondrion e. none of the listed locations | the inner membrane of the mitochondrion The electron transport chain is an energy converter that uses the exergonic flow of electrons to pump hydrogen ions across the membrane from matrix to intermembrane space. | 59 | |
| 1801586881 | The overall efficiency of respiration (the percentage of the energy released that is saved in ATP) is approximately __________. a. 0.5% b. 2% c. 35% d. 94% e. 100% | 35% The efficiency of respiration is 7.3 kcal per mole times 32 moles (maximum ATP yield per mole of glucose) divided by 686 kcal (the amount of energy contained in one mole of glucose), or about 35%. | 60 | |
| 1801586882 | When solid tumors of animals reach a certain size, the center of the tumor begins to die. To prevent this, the tumor can recruit new blood vessels. What purpose does the recruitment of blood vessels to growing tumors serve? a. It supplies glucose to the rapidly dividing cells of the tumor. b. It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation. c. It supplies a non-oxygen electron acceptor to cells so that the cells can respire anaerobically. d. It supplies a non-oxygen electron acceptor to cells so that the cells can respire anaerobically, and it supplies oxygen so that aerobic cellular respiration can occur instead of fermentation. e. It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation, and it supplies glucose to the rapidly dividing cells of the tumor. | It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation, and it supplies glucose to the rapidly dividing cells of the tumor. The new blood vessels provide the fuel for cellular respiration: oxygen and glucose. The new blood vessels also eliminate wastes such as carbon dioxide from the tumor. Some anti-cancer drugs attempt to block the process of recruitment of new blood vessels to tumors. | 61 | |
| 1801586883 | Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________. a. prevents pyruvate from accumulating b. enables the cell to recycle the reduced NADH to oxidized NAD+ c. extracts a bit more energy from glucose d. enables the cell to make pyruvate into substances it can use e. removes poisonous oxygen from the environment | enables the cell to recycle the reduced NADH to oxidized NAD+ Normally, the reduced NADH delivers its electrons to the electron transport chain, enabling NAD+ to be recycled to glycolysis. | 62 | |
| 1801586884 | Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could do this by checking for a buildup of which of the following compounds? a. lactate b. oxygen c. ATP d. ADP e. carbon dioxide | lactate In humans, muscle cells switch to lactate fermentation after becoming anaerobic. | 63 | |
| 1801586885 | In glycolysis in the absence of oxygen, cells need a way to regenerate which compound? a. carbon dioxide b. ethanol c. glucose d. NAD+ e. lactate | NAD+ The NAD+ needs to be regenerated, which is why ethanol or lactate is formed. | 64 | |
| 1801586886 | Muscle tissues make lactate from pyruvate to do which of the following? a. get rid of pyruvate produced by glycolysis b. produce additional CO2 c. utilize the energy in pyruvate d. speed up the rate of glycolysis e. regenerate NAD+ | regenerate NAD+ Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This allows them to regenerate NAD+ so that glycolysis can continue. | 65 | |
| 1801586887 | In brewing beer, maltose (a disaccharide of glucose) is __________. a. a sweetener b. the substrate for alcoholic fermentation c. the substrate for aerobic respiration d. one of the enzymes for alcoholic fermentation e. a substitute for pyruvate that cannot be made in yeast | the substrate for alcoholic fermentation In alcoholic fermentation, maltose is cleaved into two glucose molecules, which undergo glycolysis. The resulting pyruvate is converted to ethanol in two steps, one of which regenerates the supply of NAD+ needed for continued glycolysis. | 66 | |
| 1801586888 | If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result? a. The muscle cells will have more trouble making enough ATP to meet their energy requirements. b. The cells will not be able to carry out oxidative phosphorylation. c. The cells will consume glucose at an increased rate. d. Only the first two answers are correct. e. The first three answers are correct. | The first three answers are correct. Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate. | 67 | |
| 1801586889 | Of the metabolic pathways listed below, which is the only pathway found in all organisms? a. fermentation b. the citric acid cycle c. cellular respiration d. glycolysis e. the electron transport chain | glycolysis Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth's atmosphere. Glycolysis is the most widespread metabolic pathway. | 68 | |
| 1801586890 | When protein molecules are used as fuel for cellular respiration, __________ are produced as waste. a. amino groups b. sugar molecules c. molecules of lactate d. ethanol and CO2 e. fatty acids | amino groups The amino group is a residual product of amino acid catabolism. | 69 | |
| 1801586891 | A gram of fat oxidized by respiration produces approximately twice as much ATP as a gram of carbohydrate. Which of the following best explains this observation? a. Fats do not form true macromolecules as sugars do. b. Fats are better electron donors to oxygen than are sugars. c. Fats are closely related to lipid molecules, which are the basic building blocks of cellular membranes. d. Fats are produced when cells take in more food than they need. e. Fats are less soluble in water than sugars. | Fats are better electron donors to oxygen than are sugars. Fats contain more hydrogen and less oxygen than sugars—it is the transfer of electrons from good donors such as hydrogen atoms to good acceptors such as oxygen that provides the energy in respiration. | 70 | |
| 1801586892 | If significant amounts of materials are removed from the citric acid cycle to produce amino acids for protein synthesis, which of the following will result? a. Less ATP will be produced by the cell. b. Less CO2 will be produced by the cell. c. The four-carbon compound that combines with acetyl CoA will have to be made by some other process. d. The first two answers are correct. e. The first three answers are correct. | The first three answers are correct. | 71 | |
| 1802498774 | The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the a. affinity of oxygen for electrons. b. H+ concentration across the membrane holding ATP synthase. c. flow of electrons down the electron transport chain. d. transfer of phosphate to ADP. e. oxidation of glucose and other organic compounds. | H+ concentration across the membrane holding ATP synthase. | 72 | |
| 1802498775 | Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule? a. glycolysis b. the citric acid cycle c. the electron transport chain d. reduction of pyruvate to lactate e. synthesis of acetyl CoA from pyruvate | glycolysis | 73 | |
| 1802498776 | The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is a. water b. ADP c. oxygen d. NAD+ e. pyruvate | oxygen | 74 | |
| 1802498777 | In mitochondria, exergonic redox reactions a. provide the energy that establishes the proton gradient. b. reduce carbon atoms to carbon dioxide. c. are the source of energy driving prokaryotic ATP synthesis. d. are coupled via phosphorylated intermediates to ender-gonic processes. e. are directly coupled to substrate-level phosphorylation. | provide the energy that establishes the proton gradient. | 75 | |
| 1802498778 | What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ S Lactate + NAD+ a. NAD+ b. oxygen c. pyruvate d. NADH e. lactate | pyruvate | 76 | |
| 1802498779 | When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs? a. The electrons gain free energy. b. The cytochromes phosphorylate ADP to form ATP. c. NAD+ is oxidized. d. The pH of the matrix increases. e. ATP synthase pumps protons by active transport. | The pH of the matrix increases. | 77 | |
| 1802498780 | Most CO2 from catabolism is released during a. lactate fermentation. b. oxidative phosphorylation. c. glycolysis. d. electron transport. e. the citric acid cycle. | the citric acid cycle. | 78 | |
| 1813920806 | Oxygen is a requirement for anaerobic respiration. a. True b. False | False | 79 | |
| 1813920807 | If something is being reduced than it is giving up its electrons. a. True b. False | False Reduction means a substance gains electrons while oxidation is the loss of electrons. | 80 | |
| 1813920808 | With regards to the chemical equation for cellular respiration and redox reactions...what reactant is reduced and what reactant is oxidized. a. Oxygen is oxidized and glucose is reduced b. Glucose is oxidized and CO2 is reduced c. Glucose is oxidized and Oxygen is reduced d. Water is reduced and oxygen is oxidize | Glucose is oxidized and Oxygen is reduced | 81 | |
| 1813920809 | In order to produce ATP (ATP synthesis) the members of the electron transport chain are oxidized. a. True b. False | False The reduction reactions of the electron transport chain is what powers the oxidative phosphorylation of ATP synthesis. | 82 | |
| 1813920810 | Which of the following vitamins is the coenzyme NAD derived from? a. Riboflavin b. Niacin c. Sulfer d. Vitamin C e. Vitamin B12 | Niacin | 83 | |
| 1813920811 | What is the net gain of ATP at the end of glycolysis? a. 1 b. 2 c. 4 d. 8 e. 12 | 2 | 84 | |
| 1813920812 | All of the NADH's and FADH2's transport their electrons to the... a. cytosol b. matrix of mitochondria c. intermembrane space of the mitochondria d. protiens of the electron transport chain e. Choices 1 and 3 are correct f. Choices 2 and 3 and correct g. Choices 2 and 4 are correct | Choices 2 and 4 are correct | 85 | |
| 1813920813 | Which type of fermentation would be found to take place in human muscle cells? a. alcoholic fermentation b. lactic acid fermentation | lactic acid fermentation | 86 | |
| 1813920814 | Where in the cell does glycolysis take place? a. chloroplast b. mitochondrial matrix c. Mitochondrial cristae (inner membrane) d. cytosol (cytoplasm) e. lumen of the golgi | cytosol (cytoplasm) | 87 | |
| 1813920815 | A gram of fat oxidized by respiration produces more than twice as much ATP as a gram of carbohydrate. a. True b. False | True | 88 | |
| 1844237882 | 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 | 76 | 89 | |
| 1844237883 | 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% | 40% | 90 | |
| 1844237884 | 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 | creation of a proton gradient | 91 | |
| 1844237885 | 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. | energy released from movement of protons through ATP synthase | 92 | |
| 1844237886 | 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. | has an increased chemical reactivity; it is primed to do cellular work. | 93 | |
| 1844237887 | 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. | It increases the surface for oxidative phosphoryation. | 94 | |
| 1844237888 | 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 | catabolic pathways | 95 | |
| 1844237889 | 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. | ATP, CO2, and ethanol (ethyl alcohol) | 96 | |
| 1844237890 | 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) | glycolysis | 97 | |
| 1844237891 | 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 | substrate-level phosphorylation | 98 | |
| 1844237892 | 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 | mitochondrial matrix | 99 | |
| 1844237893 | 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. | It is an allosteric enzyme | 100 | |
| 1844237894 | 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. -ketoglutarate e. succinyl CoA | acetyl CoA | 101 | |
| 1844237896 | 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+ | 4 FADH2 and 12 NADH |  | 102 |
| 1844237895 | 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 | oxidation of pyruvate to acetyl CoA and the citric acid cycle | 103 |
