High School Biology : Understanding the Electron Transport Chain

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding The Electron Transport Chain

Which process of aerobic respiration does not use substrate-level phosphorylation in order to make ATP?

Possible Answers:

The electron transport chain

All options use substrate-level phosphorylation

The citric acid cycle

Glycolysis

Correct answer:

The electron transport chain

Explanation:

The electron transport chain is used to pump protons into the intermembrane space. This establishes a proton gradient, allowing protons to be pumped through ATP synthase in order to create ATP. This method of ATP production is called oxidative phosphorylation.

The other two metabolic processes, glycolysis and the citric acid cycle, use substrate-level phosphorylation to generate ATP. Substrate-level phosphorylation uses enzymes to create ATP from ADP, while oxidative phosphorylation uses the proton gradient to drive ATP synthase.

Example Question #17 : Cell Functions

Where does oxygen, the final electron acceptor, accept the electrons?

Possible Answers:

In the electron transport chain

During the citric acid cycle

During the TCA cycle

In glycolysis

During pyruvate decarboxylation

Correct answer:

In the electron transport chain

Explanation:

NADH and FADH2 are produced during glycolysis and the citric acid cycle. Electrons from these molecules are donated to proteins of the electron transport chain. The electrons interact with the proteins, helping them push protons into the intermembrane space. This accumulation of protons is what powers ATP synthesis via oxidative phosphorylation. When the electron reaches the final protein of the electron transport chain, it binds with oxygen to produce water.

Pyruvate decarboxylation convert pyruvate to acetyl CoA before the citric acid cycle. The TCA cycle is another name for the citric acid cycle.

Example Question #18 : Cell Functions

What is the primary function of the electron transport chain?

Possible Answers:

To shift protons into the intermembrane space

To directly make ATP

All of these are functions of the electron transport chain

To bring phosphates across the membrane

To give oxygen the final electrons and create water

Correct answer:

To shift protons into the intermembrane space

Explanation:

The electron transport chain is primarily used to send protons across the membrane into the intermembrane space. This create a proton-motive force, which will drive ATP synthase in the final step of cellular respiration to create ATP from ADP and a phosphate group. This final process is known as oxidative phosphorylation.

The electron is passed through proteins in the electron transport chain. With each subsequent protein, more electrons are transferred to the intermembrane space of the mitochondrion. Though oxygen is the final electron acceptor, generating water from oxygen is not the primary function of the electron transport chain.

Example Question #1 : Understanding The Electron Transport Chain

The electron transport chain is responsible for generating the proton gradient that powers the production of ATP. To where do the proteins of the electron transport chain pump these protons?

Possible Answers:

The outer mitochondrial membrane

The mitochondrial matrix

The intermembrane space

The cytosol

Correct answer:

The intermembrane space

Explanation:

As electrons move down the electron transport chain, protein pumps are provided the energy to pump protons into the intermembrane space of the mitochondrion.

The result is a high concentration of protons in the intermembrane space and a low concentration in the mitochondrial matrix. The difference in concentration and charge balance results in an electrochemical gradient, pulling protons into the mitochondrial matrix. ATP synthase is able to use this pulling force to activate enzymatic activity and generate ATP.

Example Question #2 : Understanding The Electron Transport Chain

Which of the following is not critical in ATP formation through aerobic respiration?

Possible Answers:

Electron carriers

ATP synthase

Double membrane

Proton gradient

Lactic acid

Correct answer:

Lactic acid

Explanation:

This question primarily tests your knowledge of the Electron Transport Chain, which is responsible for the majority of ATP synthesis. The Electron Transport Chain relies on the delivery of electrons from electron carriers. ATP is formed through the movement of protons down their gradient through a ATP synthase protein. The formation of the proton gradient is accomplished via a double membrane in the mitochondria. Lactic Acid is not present in aerobic respiration, instead it is a derivative of fermentation. 

Example Question #6 : Understanding The Electron Transport Chain

Which of the following is the final electron accepter of the electron transport chain?

Possible Answers:

ATP

NADH

Oxygen

Hydrogen

Correct answer:

Oxygen

Explanation:

Molecular oxygen——is the final electron accepter in cellular respiration and acts as an oxidizing agent. 

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