Chapter 9 Mastering Biology
Which statement about the citric acid cycle is correct? - The citric acid cycle depends on the availability of NAD+, which is a product of glycolysis. - The oxidation of compounds by the citric acid cycle requires molecular oxygen. - The citric acid cycle produces most of the ATP that is subsequently used by the electron transport chain. - The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle. - The citric acid cycle oxidizes glucose to carbon dioxide.
The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.
In glycolysis, ATP molecules are produced by _____.
substrate level phosphorylation
The ATP made during glycolysis is generated by - chemiosmosis. - photophosphorylation. - oxidation of NADH to NAD+. - substrate-level phosphorylation. - electron transport.
substrate-level phosphorylation.
High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of A) competitive inhibition. B) allosteric regulation. C) the specificity of enzymes for their substrates. D) an enzyme requiring a cofactor. E) positive feedback regulation.
B) allosteric regulation.
During intense exercise, as skeletal muscle cells go into anaerobiosis, the human body will increase its catabolism of A) fats only. B) carbohydrates only. C) proteins only. D) fats, carbohydrates, and proteins. E) fats and proteins only.
B) carbohydrates only.
Where does glycolysis take place in eukaryotic cells? A) mitochondrial matrix B) mitochondrial outer membrane C) mitochondrial inner membrane D) mitochondrial intermembrane space E) cytosol
Cytosol
Which of these is NOT a product of glycolysis? NADH pyruvate ATP FADH2
FADH2
In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced? -ATP is consumed, and oxygen is produced. - Glucose is consumed, and carbon dioxide is produced. - Oxygen is consumed, and glucose is produced. - Water is consumed, and ATP is produced. - Carbon dioxide is consumed, and water is produced.
Glucose is consumed, and carbon dioxide is produced.
Which of the following describes the process of glycolysis? - Glycolysis occurs in the mitochondria. - It represents the first stage in the chemical oxidation of glucose by a cell. - It converts one glucose molecule to two molecules of pyruvate and carbon dioxide. - Glycolysis produces 30 ATP from each molecule of glucose. - It requires ATP and NADH.
It represents the first stage in the chemical oxidation of glucose by a cell.
Even though plants cells photosynthesize, they still use their mitochondria for oxidation of pyruvate. When and where will this occur? - in all cells all the time in photosynthesizing cells -in the light and in other tissues in the dark - in nonphotosynthesizing cells only - in photosynthetic cells in the light, while photosynthesis occurs concurrently - in cells that are storing glucose only
in all cells all the time
The electrons stripped from glucose in cellular respiration end up in which compound? ATP water oxygen NADH carbon dioxide
water
In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain? -The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates. - The advantage of the respiratory electron transport chain is that oxygen is the final electron acceptor. - The advantage of an electron transport chain is the production of a large number of reduced, high-energy intermediates.
The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates.
Identify all correct statements about the basic function of fermentation. - The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis. - The basic function of fermentation is the production of additional ATP by further oxidation of the products of glycolysis. - The basic function of fermentation is the production of ethyl alcohol or lactic acid.
The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis.
Which of the following statements about the chemiosmotic synthesis of ATP is correct? -The energy for production of ATP from ADP comes directly from a gradient of electrons across the inner mitochondrial membrane. - Oxygen participates directly in the reaction that makes ATP from ADP and P. - The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. - The chemiosmotic synthesis of ATP occurs only in eukaryotic cells, because it occurs in mitochondria. - Chemiosmotic ATP synthesis requires oxygen.
The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane.
Which of the following statements accurately describes the function of a metabolic pathway involved in cellular respiration? -The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP. - The function of the bonding of acetic acid to the carrier molecule CoA to form acetyl CoA is the reduction of glucose to acetyl CoA. - The function of the citric acid cycle is the transfer of electrons from pyruvate to NADH to O2.
The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP.
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. These three steps result in the formation of -acetyl CoA, O2, and ATP. - acetyl CoA, NADH, H+, and CO2. -acetyl CoA, FAD, O2, and CO2. - acetyl CoA, NAD+, ATP, and CO2. - acetyl CoA, FADH2, and CO2.
acetyl CoA, NADH, H+, and CO2.
Most CO₂ from catabolism is released during A) glycolysis. B) the citric acid cycle. C) lactate fermentation. D) electron transport. E) oxidative phosphorylation.
B) the citric acid cycle.
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) acetyl CoA
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) glycolysis
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) mitochondrial inner membrane
During aerobic respiration, H₂O is formed. Where does the oxygen atom for the formation of the water come from? A) carbon dioxide (CO₂) B) glucose (C₆H₁₂O₆) C) molecular oxygen (O₂) D) pyruvate (C₃H₃O₃-) E) lactate (C₃H₅O₃-)
C) molecular oxygen (O₂)
In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO₂, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A. 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 be readily transferred to a compound in the citric acid cycle D) because it drives the reaction that regenerates NAD⁺ E) in order to remove one molecule of CO₂
C) to provide a relatively unstable molecule whose acetyl portion can be readily transferred to a compound in the citric acid cycle
Which of the following statements describes the results of this reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy -C6H12O6 is oxidized and O2 is reduced. -CO2 is reduced and O2 is oxidized. - O2 is reduced and CO2 is oxidized. -C6H12O6 is reduced and CO2 is oxidized. - O2 is oxidized and H2O is reduced.
C6H12O6 is oxidized and O2 is reduced.
Select the correct statement about cellular respiration. -Plants carry out cellular respiration only in organs such as roots that cannot carry out photosynthesis. - Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level. - Animals carry out cellular respiration whereas plants carry out photosynthesis.
Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the A) oxidation of glucose and other organic compounds. B) flow of electrons down the electron transport chain. C) affinity of oxygen for electrons. D) H⁺ concentration across the membrane holding ATP synthase. E) transfer of phosphate to ADP.
D) H⁺ concentration across the membrane holding ATP synthase.
Where is ATP synthase located in the mitochondrion? A) cytosol B) electron transport chain C) outer membrane D) inner membrane E) mitochondrial matrix
D) inner membrane
How many NADH are produced by glycolysis?
2
In glycolysis, there is a net gain of ___ ATP
2
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
2 ATP
Starting with one molecule of glucose, the energy-containing products of glycolysis are - 6 CO2, 2 pyruvate, and 2 ATP. - 6 CO2, 2 pyruvate, and 30 ATP. - 2 NAD+, 2 pyruvate, and 2 ATP. - 2 NADH, 2 pyruvate, and 2 ATP. - 2 FADH2, 2 pyruvate, and 4 ATP.
2 NADH, 2 pyruvate, and 2 ATP.
Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle (see the figure)? 38 ATP, 6 CO2, 3 NADH, and 12 FADH2 2 ATP, 2 CO2, 3 NADH, and 3 FADH2 3 ATP, 3 CO2, 3 NADH, and 3 FADH2 1 ATP, 2 CO2, 3 NADH, and 1 FADH2 3 ATP, 6 CO2, 9 NADH, and 3 FADH2
3 ATP, 6 CO2, 9 NADH, and 3 FADH2
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration? 4 60-64 2 15 30-32
60-64
Which of the following statements describes NAD⁺? A) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle. B) NAD⁺ has more chemical energy than NADH. C) NAD⁺ is oxidized 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) NAD⁺ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
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) The pH of the matrix increases.
The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion? A) active transport B) diffusion C) facilitated diffusion D) through a channel E) through a pore
A) active transport
What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions? A) glucose B) ethanol C) pyruvate D) lactic acid E) either ethanol or lactic acid
A) glucose
In glycolysis, what starts the process of glucose oxidation? FADH2 hexokinase NADPH ADP ATP
ATP
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) citric acid cycle → NADH → electron transport chain → oxygen
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) mitochondrial matrix
Which statement best supports the hypothesis that glycolysis is an ancient metabolic pathway that originated before the last universal common ancestor of life on Earth? -Glycolysis neither uses nor needs O2. Glycolysis is found in all eukaryotic cells. - Ancient prokaryotic cells, the most primitive of cells, made extensive use of glycolysis long before oxygen was present in Earth's atmosphere. - Glycolysis is widespread and is found in the domains Bacteria, Archaea, and Eukarya. - The enzymes of glycolysis are found in the cytosol rather than in a membrane-enclosed organelle.
Glycolysis is widespread and is found in the domains Bacteria, Archaea, and Eukarya.
A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose? -It was lost as heat. - It is stored in the carbon dioxide and water molecules released by these processes. - It is stored in NADH and FADH2 - It is stored in pyruvate. - It is stored in the ATP that was formed by glycolysis and the citric acid cycle.
It is stored in NADH and FADH2
During aerobic respiration, electrons travel downhill in which sequence? -glucose → pyruvate → ATP → oxygen - food → glycolysis → citric acid cycle → NADH → ATP - food → citric acid cycle → ATP → NAD+ -food → NADH → electron transport chain → oxygen - glucose → ATP → electron transport chain → NADH
food → NADH → electron transport chain → oxygen
A molecule that is phosphorylated -has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate. - has a decreased chemical reactivity; it is less likely to provide energy for cellular work. - has less energy than before its phosphorylation and therefore less energy for cellular work. - has an increased chemical potential energy; it is primed to do cellular work. - has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
has an increased chemical potential energy; it is primed to do cellular work.
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 of ATP in a cell would be expected to -activate the enzyme and increase the rates of glycolysis and the citric acid cycle. - inhibit the enzyme and thus increase the rate of glycolysis and the concentration of citrate. - inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle. - activate the enzyme and thus slow the rates of glycolysis and the citric acid cycle. - inhibit the enzyme and thus increase the rates of glycolysis and the citric acid cycle.
inhibit the enzyme and thus slow the rates of glycolysis and the citric acid cycle.
How will a healthy individual's ATP production change during an eight-hour fast?
it won't change significantly
In muscle cells, fermentation produces _____. - pyruvate - carbon dioxide, ethanol, NADH, and ATP - carbon dioxide, ethanol, and NAD+ - lactate, NADH, and ATP - lactate and NAD+
lactate and NAD+
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction - loses electrons and gains potential energy. - neither gains nor loses electrons, but gains or -loses potential energy. gains electrons and loses potential energy. - loses electrons and loses potential energy. -gains electrons and gains potential energy.
loses electrons and loses potential energy.
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration? - oxidative phosphorylation and fermentation - oxidation of pyruvate to acetyl CoA and the citric acid cycle - fermentation and glycolysis - glycolysis and the oxidation of pyruvate to acetyl CoA - the citric acid cycle and oxidative phosphorylation
oxidation of pyruvate to acetyl CoA and the citric acid cycle
One function of both alcohol fermentation and lactic acid fermentation is to - oxidize NADH to NAD+. - reduce FADH2 to FAD+. - reduce NAD+ to NADH. - reduce FAD+ to FADH2. -do none of the above.
oxidize NADH to NAD+.
In fermentation _____ is reduced and _____ is oxidized. pyruvate ... NADH lactate ... NADH NAD+ ... pyruvate lactate ... ethanol NADH ... lactate
pyruvate ... NADH
What is proton-motive force? - the force provided by a transmembrane hydrogen ion gradient -the force that moves hydrogen to NAD+ -the force that moves hydrogen into the intermembrane space -the force that moves hydrogen into the mitochondrion -the force required to remove an electron from hydrogen
the force provided by a transmembrane hydrogen ion gradient
Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration? -producing complex molecules from chemical building blocks - the breakdown of glucose to carbon dioxide and water - transforming the energy in glucose and related molecules in a chemical form that cells can use for work - breaking down ATP, so that ADP and P can be reused - catabolism of sugars and related compounds
transforming the energy in glucose and related molecules in a chemical form that cells can use for work
