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During aerobic respiration, the complete oxidation of one molecule of glucose theoretically yields 38 ATP. However, the actual yield is often lower. Which of the following is NOT a significant contributor to this reduced ATP yield?
Incomplete oxidation of glucose in the cytoplasm
Leakage of protons across the inner mitochondrial membrane
Utilization of the proton gradient for processes other than ATP synthesis
Variations in the efficiency of the electron transport chain
During alcoholic fermentation by yeast, a crucial intermediate is formed before the production of ethanol. This intermediate, which is also associated with muscle fatigue in animals, is:
Pyruvate
Lactate
Acetaldehyde
Citrate
The Pasteur effect describes the inhibitory effect of oxygen on fermentation. This inhibition is primarily due to:
Direct inhibition of fermentative enzymes by oxygen
Increased activity of the electron transport chain
Feedback inhibition of glycolytic enzymes by ATP and citrate
Depletion of NADH required for fermentation
Which enzyme is crucial for regenerating in both alcoholic and lactic acid fermentation?
Lactate dehydrogenase
Alcohol dehydrogenase
Glyceraldehyde-3-phosphate dehydrogenase
Pyruvate kinase
Under anaerobic conditions, if a cell utilizes glucose exclusively via glycolysis, what would be the net ATP yield per glucose molecule if the glyceraldehyde-3-phosphate dehydrogenase reaction is bypassed by a hypothetical enzyme that directly converts glyceraldehyde-3-phosphate to 3-phosphoglycerate without generating NADH?
0 ATP
2 ATP
4 ATP
6 ATP
A rare genetic disorder impairs the enzyme phosphoglycerate kinase. Which of the following metabolic consequences is MOST likely to be observed in an individual with this disorder?
Increased ATP production and accumulation of 3-phosphoglycerate
Reduced ATP production and accumulation of 1,3-bisphosphoglycerate
No change in ATP production but accumulation of pyruvate
Increased lactate production and depletion of NAD+
In a hypothetical scenario, a cell has a mutated form of aldolase that cleaves fructose 1,6-bisphosphate into two molecules of dihydroxyacetone phosphate. How many net ATP molecules would be produced from one molecule of glucose under anaerobic conditions in this cell?
0 ATP
2 ATP
4 ATP
6 ATP
If the standard free energy change (') for the conversion of glucose to pyruvate is -180 kJ/mol and the ' for ATP hydrolysis is -30 kJ/mol, what is the theoretical maximum number of ATP molecules that could be generated from the complete oxidation of one glucose molecule to pyruvate, assuming 100% efficiency?
3 ATP
6 ATP
9 ATP
12 ATP
Arsenic poisoning can inhibit several enzymes, including lipoic acid-containing enzymes like pyruvate dehydrogenase. How would arsenic poisoning indirectly affect glycolysis?
Arsenic directly inhibits hexokinase, the first enzyme in glycolysis.
Arsenic enhances glycolysis by stimulating phosphofructokinase activity.
By inhibiting pyruvate dehydrogenase, arsenic poisoning would lead to a buildup of pyruvate, which could in turn inhibit glycolysis through feedback mechanisms.
Arsenic has no effect on glycolysis as it specifically targets mitochondrial enzymes.
Imagine a scenario where a cell expresses a mutated form of glyceraldehyde-3-phosphate dehydrogenase that uses inorganic phosphate but does not reduce NAD+ to NADH. What is the fate of the high-energy phosphate group acquired during this altered reaction in the subsequent steps of glycolysis under anaerobic conditions?
It is lost as inorganic phosphate during the conversion to 2-phosphoglycerate.
It is transferred to ADP to form ATP by phosphoglycerate kinase.
It remains attached to the 3-carbon molecule and is ultimately incorporated into lactate.
It is used to phosphorylate another glucose molecule, priming it for entry into glycolysis.
