Chapter 9
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 ________.
Allosteric regulation
During aerobic respiration, which of the following molecules directly donates electrons to the electron transport chain at the lowest energy level?
FADH2
Which of the following statements about the electron transport chain is true?
It consists of a series of redox reactions
Most CO2 from catabolism is released during
citric acid cycle
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?
loses electrons and loses potential energy.
Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?
oxidation of NADH to NAD+
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
Which of the following statements best describes the primary role played by oxygen in cellular respiration?
serves as the final acceptor for electrons from the electron transport chain.
glycolysis, for each molecule of glucose oxidized to pyruvate, _______
two molecules of ATP are used, and four molecules of ATP are produced
Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?
100%
The oxygen consumed during cellular respiration is directly involved in which of the following processes or events?
Accepting electrons at the end if the electron transport chain
Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?
Acetyl oca
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
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.
When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes ________.
Reduced
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?
Released at CO2 and O2
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?
12.5
Beta oxidation generates substrates for cellular respiration through which of the following processes?
Catabolism of fatty acids
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
Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C6H12O6) in aerobic cellular respiration?
30-32
For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle (see the accompanying figure)?
4
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 and co2 and ethanol
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
Gkycolysis
Which of the following metabolic processes normally occurs regardless of whether or not oxygen (O2) is present?
Gkycolysis
Which of the following metabolic processes take place in the cytosol of a eukaryotic cell?
Gkycolysis and fermentation
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.
Why are carbohydrates and fats frequently considered high-energy foods?
They contain many electrons associated with hydrogen atoms.
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
During which of the following metabolic processes is most of the CO2 from the catabolism of glucose is released?
Citric acid cycle
If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to the rates of ATP and carbon dioxide production?
The rates of ATP production and carbon dioxide production would both increase.
Which of the following processes generates a proton-motive force in mitochondria?
pumping of hydrogen ions from the mitochondrial matrix across the inner membrane and into the intermembrane space
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
The immediate energy source that drives ATP synthesis by
H+ concentration gradient across the membrane holding ATP synthase.
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.
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
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.
Even though plants cells carry out photosynthesis, they still use their mitochondria for oxidation of pyruvate. Under what conditions will plant cell mitochondria be active in this process?
In all cells light or dark
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
pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure?
Oxaloacetate will accumulate and citric acid will decrease.
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
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+
Pyruvate
What is the oxidizing agent in the following reaction? Pyruvate + NADH + H- Lactate + NAD-
Pyruvate
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.
The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis. About 10% of Springer spaniels suffer from canine PFK deficiency. Given its critical role in glycolysis, which of the following conditions would be a likely consequence for dogs afflicted with this disorder?
They would be lethargic and readily tire from exercise.
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 directky enter the cuteic acid cycle
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
The ph of the matrix increases
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
Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?
2/3
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.
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 of oxidative phosphorylation
An organism is discovered that thrives in both the presence and absence of oxygen. Interestingly, as oxygen is removed from the organism's environment, the rate of sugar consumption increases while the growth rate decreases. What do these observations suggest about the likely identity of this organism?
It is a facultative anaerobic organism.
Where are the proteins of the electron transport chain located?
Mitochondiral inner membrane
Energy released by the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?
Mitochondrial intermembrane space
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 about NAD+ is true?
NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.
What happens when electrons are passed from one atom to a more electronegative atom?
The more electronegative atom is reduced, and energy is released.
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. Which of the following statements about these inside-out membrane vesicles is true?
The inside of the vesicles will become acidic when NADH is added.
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
Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." The little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. After the disruption, which components involved in oxidative phosphorylation must be present for electron transfer and ATP synthesis to still occur?
all of the electron transport system and ATP synthase
What kinds of cells carry out ATP synthesis by chemiosmosis?
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
In which reactions of cellular respiration and fermentation does substrate-level phosphorylation occur?
both glycolysis and the citric acid cycle
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
Which of the following sequences describes the path by which electrons travel downhill energetically in aerobic respiration?
glucose → NADH → electron transport chain → oxygen
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 events takes place in the electron transport chain?
the harnessing of energy from high-energy electrons derived from glycolysis and the citric acid cycle