mastering biology for cellular 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%
In glycolysis there is a net gain of _____ ATP.
2
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
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
2ATP
how many carbons are in acetyl CoA
2C
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
how many carbons are in fumarate
4C
how many carbons are in malate
4C
how many carbons are in oxaloacetate
4C
how many carbons are in succinate
4C
how many carbons are in succinyl CoA
4C
how many carbons are in alpha-ketoglutarate
5C
how many carbons are in isocitrate
6 C
how many carbons are in citrate
6C
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.
____ is the compound that functions as the electron acceptor in glycolysis.
NAD+
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
where is glycolysis located
cytosol
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
true or false The enzymes involved in ATP synthesis must be attached to a membrane to produce ATP.
false
true or false The phosphate group added to ADP to make ATP comes from free inorganic phosphate ions.
false
In glycolysis, the carbon-containing compound that functions as the electron donor is ____.
glucose
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
Photosynthesis produces _ and releases _ into the atmosphere.
glucose, oxygen
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 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
Which of the following processes is driven by chemiosmosis?
oxidative phosphorylation
When a compound donates (loses) electrons, that compound becomes ___. Such a compound is often referred to as an electron donor.
oxidized
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
oxygen
Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called _____.
pyruvate
In fermentation _____ is reduced and _____ is oxidized.
pyruvate ... NADH
what is the cycle of the citric acid cycle
pyruvate(from glycolysis) to acetyl CoA, to citrate, to isocitrate, to alpha-ketoglutarate, to succinyl CoA, to succinate, to fumarate, to malate, to oxaloacetate back to citrate
Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
pyruvate, ATP, and NADH
When a compound accepts (gains) electrons, that compound becomes ____. Such a compound is often referred to as an electron acceptor.
reduced
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
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.
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
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? -producing complex molecules from chemical building blocks -catabolism of sugars and related compounds -breaking down ATP, so that ADP and P can be reused -transforming the energy in glucose and related molecules in a chemical form that cells can use for work -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
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
true or false A bond must be broken between an organic molecule and phosphate before ATP can form.
true
true or false An enzyme is required in order for the reaction to occur
true
true or false One of the substrates is a molecule derived from the breakdown of glucose.
true
How many NADH are produced by glycolysis?
two
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 statements is not true of most cellular redox reactions? View Available Hint(s) -The reactant that is oxidized loses electrons. -The electron acceptor is reduced. -A hydrogen atom is transferred to the atom that loses an electron. -Changes in potential energy can be released as heat.
A hydrogen atom is transferred to the atom that loses an electron.
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)
aerobic oxidation
Acetyl CoA
How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)
Both electron transport and ATP synthesis would stop.
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. -O2 is oxidized and H2O is reduced. -O2 is reduced and CO2 is oxidized. -CO2 is reduced and O2 is oxidized.
C6H12O6 is oxidized and O2 is reduced.
pyruvate is oxidized to
CO2
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. Animals carry out cellular respiration whereas plants carry out photosynthesis. 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.
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.
Which stage of glucose metabolism produces the most ATP?
Electron transport and chemiosmosis
During aerobic respiration, which of the following molecules directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
FAD is reduced to
FADH2
Which of these is NOT a product of glycolysis? -pyruvate -NADH -ATP -FADH2
FADH2
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.
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 step of the cellular respiration pathway can take place in the absence of oxygen?
Glycolysis
The electrons stripped from glucose in cellular respiration end up in which compound?
H2O
Which of the following statements about the electron transport chain is true? It includes a series of hydrolysis reactions associated with mitochondrial membranes. It is driven by ATP hydrolysis. It occurs in the cytoplasm of both prokaryotic and eukaryotic cells. It consists of a series of redox reactions
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
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? -Glycolysis produces 30 ATP from each molecule of glucose. -It requires ATP and NADH. -It converts one glucose molecule to two molecules of pyruvate and carbon dioxide. -It represents the first stage in the chemical oxidation of glucose by a cell. -Glycolysis occurs in the mitochondria.
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. It oxidizes glucose to form two molecules of pyruvate. It serves as an acceptor for carbon, forming CO2 in the citric acid cycle. It yields energy in the form of ATP as it is passed down the electron transport chain.
It serves as the final acceptor for electrons from the electron transport chain.
Which of the following statements about NAD+ is true? -In the absence of NAD+, glycolysis can still function. -NAD+ can donate electrons for use in oxidative phosphorylation. -NAD+ has more chemical energy than NADH. -NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
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
NAD+ is reduced to
NADH
The reduced form of the electron acceptor in glycolysis is ____.
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? Water is the last electron acceptor. Electrons gain energy as they move down the chain NADH and FADH2 donate their electrons to the chain. The electron transport chain is the first step in cellular respiration.
NADH and FADH2 donate their electrons to the chain.
what are the reactants in the anaerobic reduction of pyruvate during lactic acid fermentation.
NADH, pyruvate
Which of the following statements is true of the bonds in a water molecule? View Available Hint(s) -Oxygen acts as the electron acceptor and is oxidized. -There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero. -The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1. -Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.
Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.
Given what you know about glycolysis and regulation of metabolism by PFK, what is the likely mechanism by which PFK activity differs depending on ATP concentration?
PFK is an allosteric enzyme that is inhibited by ATP and stimulated by AMP.
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.
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
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 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 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 produces most of the ATP that is subsequently used by the electron transport chain. -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.
Which of the following is true for all exergonic reactions? -The reaction goes only in a forward direction: All reactants will be converted to products. -The reaction proceeds with a net release of free energy. -A net input of energy from the surroundings is required for the reactions to proceed. -The products have more total energy than the reactants.
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.
Which of the following is true of the energy levels of electrons in shells? -Electrons must lose energy to move from the first to the second shell. -Electrons do not have potential energy, just kinetic energy. -Valence electrons have a higher energy level than those in other filled shells. -All the electrons in an atom have similar energy levels.
Valence electrons have a higher energy level than those in other filled shells.
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
Which of these enters the citric acid cycle? G3P acetyl CoA glucose NADH + H+ pyruvate
acetyl CoA
Which of these is NOT a product of the citric acid cycle? NADH + H+ ATP CO2 acetyl CoA FADH2
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
Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?
carbon dioxide
The carbon in glucose is oxidized to _ during cellular respiration.
carbon dioxide
_ and _ are by-products of cellular respiration.
carbon dioxide, water
what are the sites of photosynthesis.
chloroplasts
Where is oxidative phosphorylation located?
inner mitochondrial membrane
What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?
ionic
fermentation in human muscle
lactate
In muscle cells, fermentation produces _____.
lactate and NAD+
what are the products in the anaerobic reduction of pyruvate during lactic acid fermentation.
lactate, NAD+
what are the sites of cellular respiration.
mitochondria
Energy released by the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?
mitochondrial intermembrane space
Where is the citric acid cycle located?
mitochondrial matrix
where is acetyl CoA formation located
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)
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? reduction of NAD+ to NADH hydrolysis of ATP to ADP + i oxidation of NADH to NAD+ reduction of FAD to FADH2
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
