REVIEW QUESTIONS
In this lesson, you learned how cells couple the catabolic breakdown of molecules to the synthesis of high-energy molecules like NADH and ATP. You also learned how these molecules can act like energy currencies, since they allow the energy from catabolism to fuel many endergonic processes, without the need for separate enzymes to link every exergonic process to every endergonic process.
As you answer the following questions, try not to get caught up in the details of molecule and enzyme names. Pay attention to the underlying principles of biochemistry that you’ve learned.
Question 1
1 point possible (graded)
Consider the reaction shown below.
The enzyme acetyl-CoA carboxylase couples the thermodynamically ____________ carboxylation of acetyl-CoA to the thermodynamically ____________ hydrolysis of ATP.
• unfavorable; unfavorable
• unfavorable; favorable
• favorable; unfavorable
• favorable; favorable
Question 2
1 point possible (graded)
In ____________ reactions, certain molecules are broken down; in the process they release energy which is captured when high-energy molecules (such as NADH and ATP) are formed. The breakdown of these molecules can then be coupled to thermodynamically unfavorable processes such as ____________ reactions or pumping hydrogen ions from ____________ to ____________ concentration areas.
anabolic; catabolic; high; low
catabolic; anabolic; high; low
anabolic; catabolic; low; high
catabolic; anabolic; low; high
Question 3
0.0/1.0 point (graded)
Rotenone is a commonly used insecticide (poison that kills insects) that inhibits the electron transport chain by preventing complex I from passing electrons to coenzyme Q. What redox states would you expect to observe in the ETC of mitochondria in insects poisoned with rotenone relative to healthy insects? Select the correct redox state for each of the components of the ETC listed below. For this question, assume that NADH is the sole source of electrons entering the electron transport chain. Note that each answer may be used once, more than once, or not at all.
Molecule
Redox state
coenzyme Q
oxidized reduced
unanswered
complex I
oxidized reduced
unanswered
complex III
oxidized reduced
complex IV
oxidized reduced
cytochrome C
oxidized reduced
Question 4
1 point possible (graded)
Would you expect the concentration of hydrogen ions in the matrix of rotenone-poisoned mitochondria to increase, decrease or remain about the same relative to mitochondria that are not poisoned with rotenone?
increase
decrease
remain about the same
Question 5
1 point possible (graded)
Which of the following would you expect to observe in the cells of insects poisoned with rotenone? (select two answers)
increased activity of the regulated enzymes of gluconeogenesis
increased activity of the regulated enzymes of glycolysis
increased lactate fermentation
increased O2 consumption
increased cellular ATP
Question 6
1 point possible (graded)
The catabolic pathways that degrade fatty acids do not generate ATP directly, but produce NADH and acetyl-CoA. Given what you know about cellular metabolism, which of the following enzymes is required to completely break down fatty acids?
acetyl-CoA carboxylase, which catalyzes the formation of malonyl-CoA from acetyl-CoA
pyruvate dehydrogenase, which catalyzes the formation of acetyl-CoA from pyruvate
fumarase, which catalyzes the conversion of fumarate to malate in the TCA cycle
lactate dehydrogenase, which catalyzes the fermentation of pyruvate into lactate
Question 7
1 point possible (graded)
What molecules in the list below can contribute to ATP synthesis in the absence of oxygen? (select two answers)
• Palmitate (a 16-carbon fatty acid)
• Acetyl-CoA
• Glycogen
• Glucose
• NADH
Question 8
0.0/1.0 point (graded)
Suppose you have a patient who has been poisoned with either DNP or cyanide, but you do not know which. Recall that cyanide inhibits the oxidation of complex IV by oxygen, leading to an accumulation of reduced ETC components. By contrast, DNP disrupts the hydrogen ion gradient in mitochondria without interfering with the activity of the ETC.
Would you expect to see the following in cells exposed to DNP, cyanide, both, or neither, assuming you could test these conditions in the patient’s cells? Select the metabolic poison(s) that could cause each of the following observations. Note that each answer may be used once, more than once, or not at all.
Observation
Metabolic poison
Increased activity of regulated enzymes in glycolysis
Select an option cyanide DNP both neither
unanswered
Decreased cellular ATP production
Select an option cyanide DNP both neither
unanswered
Increased production of lactic acid
Select an option cyanide DNP both neither
unanswered
Increased consumption of oxygen
Select an option cyanide DNP both neither
unanswered
Increased oxidation of fatty acids
Select an option cyanide DNP both neither
Question 9
1 point possible (graded)
In Reduction/Oxidation reactions, one molecule loses electrons and another molecule gains electrons
The figure below depicts a reaction that occurs in the TCA cycle. This reaction is catalyzed by succinate dehydrogenase.
Which of the statements below best describes this reaction?
• Succinate is oxidized by FAD, gaining energy in the process.
• Succinate is reduced by FAD, gaining energy in the process.
• Succinate is oxidized by FAD, losing energy in the process.
• Succinate is reduced by FAD, losing energy in the process.
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