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?
answer
They would be lethargic and readily tire from exercise.
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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?
answer
His mitochondria lacks the transport protein that moves pyruvate across the outer mitochondrial membrane.
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New biosensors, applied like a temporary tattoo for 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 lactase, 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 their lactate levels?
answer
During anaerobic respiration, lactate levels increase when muscle cells need more energy; however, muscle cells eventually fatigue, thus athletes should modify their activities to increase aerobic respiration.
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In chemiosmosis, what is the most direct source of energy that is used to convert ADP +Pi to ATP?
answer
Energy released from movement of protons through ATP synthase, down their electrochemical gradient
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Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops. Which of these statements is the correct explanation for this observation?
answer
In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration.
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The rate of cellular respiration is regulated by its major product, ATP, via feedback inhibition. As the diagram shows, high levels of ATP inhibit phosphofructokinase (PFK), an early enzyme in glycolysis. As a result, the rate of cellular respiration, and thus ATP production, decreases. Feedback inhibition enables cells to adjust their rate of cellular respiration to match their demand for ATP. Suppose that a cell's demand for ATP suddenly exceeds its supply of ATP from cellular respiration. Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?
answer
ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.
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Under anaerobic conditions (a lack of oxygen), glycolysis continues in most cells despite the fact that oxidative phosphorylation stops, and its production of NAD+ (which is needed as an input to glycolysis) also stops. The diagram illustrates the process of fermentation, which is used by many cells in the absence of oxygen. In fermentation, the NADH produced by glycolysis is used to reduce the pyruvate produced by glycolysis to either lactate or ethanol. Fermentation results in a net production of 2 ATP per glucose molecule. During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell's demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions. What would happen to the cell's rate of glucose utilization?
answer
Glucose utilization would increase a lot.
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Which statement about the citric acid cycle is correct?
answer
The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.
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Based on the graph, is PFK more active at low or high ATP concentrations?
answer
PFK is more active at low ATP concentrations.
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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?
answer
PFK is an allosteric enzyme that is inhibited by ATP and stimulated by AMP
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What happens to a glucose molecule when it loses a hydrogen atom as the result of an oxidation-reduction reaction?
answer
The glucose molecule is oxidized.
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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?
answer
ATP, CO2, and ethanol (ethyl alcohol)
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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?
answer
They would directly enter the citric acid cycle.
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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?
answer
Catabolic processes are activated that generate more ATP.
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In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?
answer
Glucose is consumed, and carbon dioxide is produced.
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Use the following information to answer the question below. The citric acid cycle. Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle?
answer
3 ATP, 6 CO2, 9 NADH, and 3 FADH2
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Which of the following processes is driven by chemiosmosis?
answer
Oxidative phosphorylation
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In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
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two ATP
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Which of the following statements best describes the primary role played by oxygen in cellular respiration?
answer
It serves as the final acceptor for electrons from the electron transport chain.
question
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?
answer
All of the electron transport system and ATP synthase.
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In glycolysis, as in all the stages of cellular respiration, the transfer of electrons from electron donors to electron acceptors plays a critical role in the overall conversion of the energy in foods to energy in ATP. These reactions involving electron transfers are known as oxidation-reduction, or redox, reactions. Drag the words on the left to the appropriate blanks on the right to complete the sentences.
answer
When a compound donates (loses) electrons, that compound becomes oxidized. Such a compound is often referred to as an electron donor. When a compound accepts (gains) electrons, that compound becomes reduced. Such a compound is often referred to as an electron acceptor. In glycolysis, the carbon-containing compound that functions as the electron donor is glucose. Once the electron donor in glycolysis gives up its electrons, it is oxidized to a compound called pyruvate. NAD+ is the compound that functions as the electron acceptor in glycolysis. The reduced form of the electron acceptor in glycolysis is NADH.
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Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?
answer
pyruvate, ATP, and NADH
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The ATP that is generated in glycolysis is produced by substrate-level phosphorylation, a very different mechanism than the one used to produce ATP during oxidative phosphorylation. Phosphorylation reactions involve the addition of a phosphate group to another molecule. Sort the statements into the appropriate bin depending on whether or not they correctly describe some aspect of substrate-level phosphorylation in glycolysis.
answer
Correct statements- One of the substrates is a molecule derived from the breakdown of glucose. An enzyme is required in order for the reaction to occur. A bond must be broken between an organic molecuel and phosphate before ATP can form. Incorrect statements- the phosphate group added to ADP to make ATP comes from free inorganic phosphate ions. The enzymes involved in ATP synthesis must be attached to a membrane to produce ATP.
question
Two molecules with the chemical formulas C6H12O6and C6H12O2are probably
answer
a monosaccharide and a fatty acid
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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?
answer
12.5
question
Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?
answer
glucose
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Starting with one molecule of glucose, glycolysis results in the net production of which of the following sets of energy-containing products?
answer
2 NADH, 2 pyruvate, and 2 ATP
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From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of glycolysis. Drag each compound to the appropriate bin. If the compound is not involved in glycolysis, drag it to the "not input or output" bin.
answer
Net input: NAD+, ADP, glucose. Net output: NADH, ATP, pyruvate. Not input or output: acetyl CoA, CO2, O2, and coenzyme A.
question
In acetyl CoA formation, the carbon-containing compound from glycolysis is oxidized to produce acetyl CoA. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of acetyl CoA formation. Drag each compound to the appropriate bin. If a compound is not involved in acetyl CoA formation, drag it to the "not input or output" bin. (Note that not all of the inputs or outputs of acetyl CoA formation are included).
answer
Net input: NAD+, coenzyme A, and pyruvate. Net output: NADH, acetyl CoA, CO2. Not input or output: ADP, ATP, glucose, or O2.
question
In the citric acid cycle (also known as the Krebs cycle), acetyl CoA is completely oxidized. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of the citric acid cycle. Drag each compound to the appropriate bin. If a compound is not involved in the citric acid cycle, drag it to the "not input or output" bin. (Note that not all of the inputs and outputs of the citric acid cycle are included.)
answer
Net input: acetyl CoA, NAD+, and ADP. net output: coenzyme A, CO2, NADH, ATP. Not input or output: pyruvate, glucose, and O2.
question
In the last stage of cellular respiration, oxidative phosphorylation, all of the reduced electron carriers produced in the previous stages are oxidized by oxygen via the electron transport chain. The energy from this oxidation is stored in a form that is used by most other energy-requiring reactions in cells. From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of oxidative phosphorylation. Drag each compound to the appropriate bin. If a compound is not involved in oxidative phosphorylation, drag it to the "not input or output" bin. (Note that not all of the inputs and outputs of oxidative phosphorylation are listed).
answer
Net input: NADH, ADP, and O2. Net output: NAD+, ATP, water. Not input or output: glucose, pyruvate, acetyl CoA, coenzyme A, and CO2.
question
Each of the four stages of cellular respiration occurs in a specific location inside or outside the mitochondria. These locations permit precise regulation and partitioning of cellular resources to optimize the utilization of cellular energy. match each stage of cellular respiration with the cellular location in which it occurs. Labels may be used once, more than once, or not at all.
