Chapter 7 life 120
Why are carbohydrates and fats considered high-energy foods?
They have a lot of electrons associated with hydrogen.
Inside an active mitochondrion, most electrons follow which pathway?
citric acid cycle-->NADH--> electron transport chain--> oxygen
Where does glycolysis take place in eukaryotic cells?
cytosol
Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?
in all cells all the time
In chemiosmosis, what is the most direct source of energy that is used to convert ADP + i to ATP?
energy released from movement of protons through ATP synthase, down their electrochemical gradient
During aerobic respiration, electrons travel downhill in which sequence?
food --> NADH -->electron transport chain --> oxygen
What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?
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
Which metabolic pathway is common to both cellular respiration and fermentation?
glycolysis
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
glycolysis
Which of the following normally occurs regardless of whether or not oxygen (O2) is present?
glycolysis
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
glycolysis
Which of the following occur(s) in the cytosol of a eukaryotic cell?
glycolysis and fermentation
Which catabolic processes may have been used by cells on ancient Earth before free oxygen became available?
glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen
In prokaryotes, the respiratory electron transport chain is located
in the plasma membrane.
Where is ATP synthase located in the mitochondrion?
inner membrane
A molecule that is phosphorylated
has an increased chemical potential energy; it is primed to do cellular work.
How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
2
Starting with one molecule of glucose, the energy-containing products of glycolysis are
2 NADH, 2 pyruvate, and 2 ATP.
What fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle, if glucose is the sole energy source?
2/3
Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in
all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors.
Which kind of metabolic poison would most directly interfere with glycolysis?
an agent that closely mimics the structure of glucose but is not metabolized
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
an endergonic reaction coupled to an exergonic reaction.
An organism is discovered that thrives both in the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism
is a facultative anaerobe.
During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?
molecular oxygen (O2)
Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?
oxidative phosphorylation (chemiosmosis)
One function of both alcohol fermentation and lactic acid fermentation is to
oxidize NADH to NAD+.
When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes
oxidized.
The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is
oxygen.
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ --> Lactate + NAD+
pyruvate
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes
reduced.
In alcohol fermentation, NAD+ is regenerated from NADH by
reduction of acetaldehyde to ethanol (ethyl alcohol).
During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is
retained in the two pyruvates.
An electron loses potential energy when it
shifts to a more electronegative atom.
The ATP made during fermentation is generated by which of the following?
substrate-level phosphorylation
The ATP made during glycolysis is generated by
substrate-level phosphorylation.
Most CO2 from catabolism is released during
the citric acid cycle.
When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is
the creation of a proton-motive force.
What is proton-motive force?
the force provided by a transmembrane hydrogen ion gradient
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 is widespread and is found in the domains Bacteria, Archaea, and Eukarya.
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the
H+ movement down its concentration gradient
In glycolysis, for each molecule of glucose oxidized to pyruvate
two molecules of ATP are used and four molecules of ATP are produced.
If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately how many ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?
14
In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of
ATP, CO2, and ethanol (ethyl alcohol).
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
100%
How many oxygen molecules (O2) are required each time a molecule of glucose (C6H12O6) is completely oxidized to carbon dioxide and water via aerobic respiration?
6
Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration?
60-64
In a mitochondrion, if the matrix ATP concentration is high, and the intermembrane space proton concentration is too low to generate sufficient proton-motive force, then
ATP synthase will hydrolyze ATP and pump protons into the intermembrane space.
Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport of protons across the membrane. What will occur in the brown fat cells when they produce thermogenin?
ATP synthesis will decrease, and heat generation will increase.
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.
Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?
Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).
During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. Of the following, which is the best explanation of the dog's condition?
His mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane.
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.
When an individual is exercising heavily and when the muscle becomes oxygen-deprived, muscle cells convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?
It is taken to the liver and converted back to pyruvate.
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 How does the addition of coenzyme A, a sulfur-containing molecule derived from a B vitamin, function in the subsequent reaction?
It provides a relatively unstable molecule whose acetyl portion can be readily transferred to a compound in the citric acid cycle.
Why is glycolysis described as having an investment phase and a payoff phase?
It uses stored ATP and then forms a net increase in ATP.
You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body?
It was released as CO2 and H2O.
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.
Which of the following statements describes NAD+?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
In addition to ATP, what are the end products of glycolysis?
NADH and pyruvate
When electrons move closer to a more electronegative atom, what happens?
The more electronegative atom is reduced, and energy is released.
A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells?
The mutant yeast will be unable to grow anaerobically.
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The pH of the matrix increases.
In cellular respiration, the energy for most ATP synthesis is supplied by
a proton gradient across a membrane.
The oxygen consumed during cellular respiration is involved directly in which process or event?
accepting electrons at the end of the electron transport chain
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 one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
acetyl CoA
Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?
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. These three steps result in the formation of
acetyl CoA, NADH, H+, and CO2.
The primary role of oxygen in cellular respiration is to
act as an acceptor for electrons and hydrogen, forming water.
What is the purpose of beta oxidation in respiration?
breakdown of fatty acids
During intense exercise, as skeletal muscle cells switch to fermentation, the human body will increase its catabolism of
carbohydrates only.
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
catabolic pathways
The molecule that functions as the reducing agent (electron donor) in a redox or oxidation- reduction reaction
loses electrons and loses potential energy.
Where are the proteins of the electron transport chain located?
mitochondrial inner membrane
nergy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?
mitochondrial intermembrane space
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
The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is
the proton-motive force across the inner mitochondrial membrane.
In vertebrate animals, brown fat tissue's color is due to abundant blood vessels and capillaries. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue?
to regulate temperature by converting most of the energy from NADH oxidation to heat