Biochemistry 5 Views 1 Answers
Which of the following best describes the electron transport chain? A Electrons are pumped across a membrane by active transport. B Acetyl CoA is fully oxidized to CO2. C Hydrogen atoms are added to CO2 to make an energy-rich compound. D Glucose is broken down to a three-carbon compound in preparation for the citric acid cycle. E Electrons are passed from one carrier to another, releasing a little energy at each step.
Which of the following best describes the electron transport chain?
A Electrons are pumped across a membrane by active transport.
B Acetyl CoA is fully oxidized to CO2.
C Hydrogen atoms are added to CO2 to make an energy-rich compound.
D Glucose is broken down to a three-carbon compound in preparation for the citric acid cycle.
E Electrons are passed from one carrier to another, releasing a little energy at each step.
Answered
The correct answer is:
E. Electrons are passed from one carrier to another, releasing a little energy at each step.
Explanation:
- In the electron transport chain (ETC), electrons from NADH and FADH2 are passed through a series of protein complexes (such as NADH dehydrogenase, cytochrome c reductase, and cytochrome c oxidase). As electrons move through these carriers, they release small amounts of energy, which is used to pump protons (H+^+) across the inner mitochondrial membrane, establishing a proton gradient. This energy is ultimately used to produce ATP.
Why the other options are incorrect:
- A (Incorrect): Electrons are not directly pumped across the membrane; instead, the energy from the electrons is used to pump protons across the membrane.
- B (Incorrect): Acetyl CoA is fully oxidized to CO2 in the citric acid cycle, not the electron transport chain.
- C (Incorrect): Hydrogen atoms are not added to CO2 in the electron transport chain. CO2 is a byproduct of the citric acid cycle.
- D (Incorrect): Glucose is broken down into pyruvate during glycolysis, not in preparation for the citric acid cycle.
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