Mastering Biology Ch. 10 (Cell Respiration)
If glucose is the sole energy source, what fraction of the carbon dioxide exhaled by animals is generated only by the reactions involved in oxidation of pyruvate to acetyl CoA?
1/3
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
100%
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, glycolysis results in the net production of which of the following sets of energy-containing products?
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?
3 ATP, 6 CO2, 9 NADH, and 3 FADH2
For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle?
4
In glycolysis, what starts the process of glucose oxidation?
ATP
The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. PFK is inhibited by high levels of which of the following molecules?
ATP and citrate
In the absence of oxygen, yeast cells can obtain energy by fermentation, which results in the production of which of the following sets of molecules?
ATP, CO2, and ethanol (ethyl alcohol)
Which of the summary statements below describes the results of the following reaction? C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced
During aerobic respiration, which of the following molecules directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
Which of these is NOT a product of glycolysis?
FADH2
Which of the following statements about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle
Following glycolysis and the citric acid cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is stored in the form of which of the following molecules?
NADH
Which electron carrier(s) function in the citric acid cycle?
NADH and FADH2
Which of the following statements about the electron transport chain is true?
NADH and FADH2 donate their electrons to the chain
What are the reactants and products in the anaerobic reduction of pyruvate during lactic acid fermentation?
Reactants- pyruvate and NADH Products- lactate and NAD+
Which of the following statements is not true of most cellular redox reactions?
a hydrogen atom is transferred to the atom that loses an electron
Two molecules with the chemical formulas C6H12O6 and C6H12O2 are probably...
a monosaccharide and a fatty acid
The oxygen consumed during cellular respiration is directly involved in which of the following processes or events?
accepting electrons at the end of the electron transport chain
Aerobic oxidation...
acetyl CoA
Which of these enters the citric acid cycle?
acetyl CoA
Which of these is NOT a product of the citric acid cycle?
acetyl CoA
Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
acetyl CoA
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. Which of the following sets of products result from these reactions?
acetyl CoA, NADH, and CO2
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?
anion and cation
How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation?
both electron transport and ATP synthesis would stop
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
carbon dioxide
A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?
catabolic processes are activated that generate more ATP
Select the correct statement about cellular respiration.
cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level
The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of which of the following processes?
coupling of an endergonic reaction to an exergonic reaction
Glycolysis occurs in the __________.
cytosol
New biosensors, applied like a temporary tattoo to the skin, can alert serious athletes that they are about to "hit the wall" and will find it difficult to continue exercising. These biosensors monitor lactate, a form of lactic acid, released in sweat during strenuous exercise. Which of the statements below is the best explanation of why athletes would need to monitor lactate levels?
during anaerobic respiration, lactate levels increase when muscles cells need more energy; however, muscles cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration
Which stage of glucose metabolism produces the most ATP?
electron transport and chemiosmosis
Which term describes the degree to which an element attracts electrons?
electronegativity
In chemiosmosis, what is the most direct source of energy that is used to convert ADP +Pi to ATP?
energy released from movement of protons through ATP synthase, down their electrochemical gradient
Fermentation in yeast and bacteria...
ethanol
Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?
fermentation
NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule.
fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor
Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP?
glucose
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
glucose
In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?
glucose is consumed, and carbon dioxide is produced
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
Which of the following metabolic processes normally occurs regardless of whether or not oxygen (O2) is present?
glycolysis
Which step of the cellular respiration pathway can take place in the absence of oxygen?
glycolysis
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
glycolysis and fermentation
Gaseous hydrogen burns in the presence of oxygen to form water: 2H2 + O2 → 2H2 O + energy Which molecule is oxidized and what kind of bond is formed?
hydrogen, polar
Oxidative phosphorylation occurs in the __________.
inner mitochondrial membrane
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
ionic
Which of the following statements about the electron transport chain is true?
it consists of a series of redox reactions
Why is glycolysis considered to be one of the first metabolic pathways to have evolved?
it does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms
In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?
it increases the surface for oxidative phosphorylation
In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction.
it is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compound such as acetyl CoA
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 is stored in NADH and FADH2
Which of the following statements describes what happens to a molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction?
it loses electrons and loses potential energy
Which of the following describes the process of glycolysis?
it represents the first stage in the chemical oxidation of glucose by a cell
Which of the following statements best describes the primary role played by oxygen in cellular respiration?
it serves as the final acceptor for electrons from the electron transport chain
A person on a strict diet and exercise regimen lost 7 kg (about 15 pounds) of body fat in just two weeks. What is the most likely way that the lost fat left the body?
it was released as CO2 and H2O
Fermentation in human muscle...
lactate
In muscle cells, fermentation produces _____.
lactate and NAD+
Energy released by the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?
mitochondrial intermembrane space
Acetyl CoA formation occurs in the __________.
mitochondrial matrix
The citric acid cycle occurs in the __________.
mitochondrial matrix
Water is one of the end products of aerobic respiration. What is the source of the oxygen atom used in formation of the water?
molecular oxygen (O2)
The free energy for the oxidation of glucose to CO2 and water is -686 kcal/mol, and the free energy for the reduction of NAD+ to NADH is +53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when it appears that as many as a dozen could be formed?
most of the free energy available from the oxidation of glucose remains in pyruvate, one of the products of glycolysis
A covalent bond is likely to be polar when...
one of the atoms sharing electrons is more electronegative than the other
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
oxidation of pyruvate to acetyl CoA and the citric acid cycle
Which of the following processes is driven by chemiosmosis?
oxidative phosphorylation
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is...
oxygen
Which of the following statements is true of the bonds in a water molecule?
oxygen holds electrons more tightly than hydrogen does, and the net charge is zero
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH
In fermentation _____ is reduced and _____ is oxidized.
pyruvate... NADH
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes _____.
reduced
In glycolysis, ATP molecules are produced by _____.
substrate-level phosphorylation
In the citric acid cycle, ATP molecules are produced by _____.
substrate-level phosphorylation
Which of the following statements about the chemiosmotic synthesis of ATP is correct?
the chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane
During which of the following metabolic processes is most of the CO2 from the catabolism of glucose is released?
the citric acid cycle
Most CO2 from catabolism is released during...
the citric acid cycle
What happens to a glucose molecule when it loses a hydrogen atom as the result of an oxidation-reduction reaction?
the glucose molecule is oxidized
Which of the following events takes place in the electron transport chain?
the harnessing of energy from high-energy electrons derived from glycolysis and the citric acid cycle
How will a healthy individual's ATP production change during an eight-hour fast?
the individual's ATP production will not change significantly
Which statement about the citric acid cycle is correct?
the last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle
Which of the following is true for all exergonic reactions?
the reaction proceeds with a net release of free energy
Why are carbohydrates and fats frequently considered high-energy foods?
they contain many electrons associated with hydrogen atoms
Fatty acids usually have an even number of carbons in their structures. Catabolism of fatty acids produces two-carbon fragments that are converted to acetyl CoA molecules. What is the most likely way in which these acetyl CoA molecules would be metabolized in aerobic cellular respiration?
they would directly enter the citric acid cycle
In mitochondrial electron transport, what is the direct role of O2?
to function as the final electron acceptor in the electron transport chain
Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration?
transforming the energy in glucose and related molecules in a chemical form that cells can use for work
True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.
true
True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.
true
In glycolysis, for each molecule of glucose oxidized to pyruvate, ________.
two molecules of ATP are used, and four molecules of ATP are produced
Which of the following is true of the energy levels of electrons in shells?
valence electrons have a higher energy level than those in other filled shells
The electrons stripped from glucose in cellular respiration end up in which compound?
water
