AP Biology : Understanding the Electron Transport Chain

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #91 : Cell Functions

What is the final electron acceptor in the electron transport chain?

Possible Answers:

Correct answer:

Explanation:

The final electron acceptor in the electron transport chain is oxygen. It gets reduced by accepting two electrons and two protons from the ATP synthase to form water via the following equation:

Example Question #100 : Cellular Respiration

Based on the concentrations of hydrogen ions in the mitochondria, where would you expect to find the most acidic environment?

Possible Answers:

Mitochondrial matrix

Cytoplasm

Intermembrane space

Inner mitochondrial membrane

Cytoplasm

Correct answer:

Intermembrane space

Explanation:

The most acidic environment, or the lowest pH, would be found in the intermembrane space. This is because as  and  pass their electrons to the enzymes in the electron transport chain, protons are pumped into the intermembrane space. This is where a high concentration protons is generated, which is considered acidic. The low concentration of protons is generated in the mitochondrial matrix rendering it basic.

Example Question #101 : Cellular Respiration

How many  do  and  produce respectively?

Possible Answers:

1.5 each

2 and 1

1 and 2

2 and 3

3 and 2

Correct answer:

3 and 2

Explanation:

Each  produces 3  molecules in the electron transport chain while each  produces 2  molecules. Each glucose molecule results in the formation of 10  molecules, which go on to produce 30 . Each glucose molecule results in the formation of 2  molecules, which go on to produce 4 . Note that some references may indicate that each  produces 2.5 , while each  produces 1.5 . These are theoretical maximums and depend on the organism, cell type, and cellular environment.

Example Question #101 : Cellular Respiration

Ideally, how many ATP molecules are produced from one glucose molecule in cellular respiration?

Possible Answers:

40

25

20

30

38

Correct answer:

38

Explanation:

A total of 38 ATP molecules are produced from one molecule of glucose. 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and about 34 ATP from the electron transport chain. Note that this is a theoretical maximum and is rarely seen in nature.

Example Question #102 : Cell Functions

The movement of electrons down a potential energy gradient during electron transport is coupled to the movement of what?

Possible Answers:

Electrons against their concentration gradient

Water down its concentration gradient.

Protons against their concentration gradient

Protons down their concentration gradient

ATP down its concentration gradient

Correct answer:

Protons against their concentration gradient

Explanation:

In electron transport, the energy that is released as electrons flow down a potential energy gradient is coupled to the movement of protons from the mitochondrial matrix across the inner mitochondrial membrane into the intermembrane space. This direction of flow is against the protons' concentration gradient and thus requires energy, which is provided by the spontaneous passage of electron down a potential energy gradient of enzyme complexes.

Example Question #103 : Cell Functions

In the Krebs cycle what are the two electron carriers that accept the hydrogen ions and then are used in the electron transport chain?

Possible Answers:

ATP and ADP

Hydrogen and oxygen

Carbon dioxide and nitrogen

Correct answer:

Explanation:

 are the two electron carriers in the Krebs cycle. ATP is the energy compound that is created in respiration. Carbon dioxide is a waste product from the Krebs cycle.  Nitrogen is not involved in the Krebs cycle. Oxygen is an electron acceptor, and hydrogen is added to the electron carriers.

Example Question #104 : Cell Functions

What is the primary reason that ATP synthesis occurs with the electron transport chain?

Possible Answers:

ATP is created by breaking down water as the water passes through the pumps in the membranes.

NADH pass through ATP synthase, which creates ATP

A concentration gradient of protons is created across the membranes of the mitochondria and then the protons feed into ATP synthase, creating ATP.

ADP accepts a protons ion and a phosphate to create ATP.

Correct answer:

A concentration gradient of protons is created across the membranes of the mitochondria and then the protons feed into ATP synthase, creating ATP.

Explanation:

The concentration gradient of protons feeds into ATP synthase structure, which creates ATP. Water does not feed into ATP synthase. ADP does not accept the hydrogen to create ATP, rather it is the substrate onto which a phosphate group is added to create ATP. NADH gives up a hydrogen in the electron transport chain to create the concentration gradient. It does not pass through ATP synthase.

Example Question #105 : Cell Functions

While looking under her microscope, Dr. Smith noticed the cell was packed with mitochondria. While thinking back to the basics of the cell, she remembered on of the unique properties of this organelle is its ability to produce large amounts of energy in the form of ATP. Where do we find the major components of the electron transport chain?

Possible Answers:

Intermembrane space

Outer membrane

Matrix

The electron transport chain is not found in the mitochondria

Inner membrane 

Correct answer:

Inner membrane 

Explanation:

The mitochondrion is composed of an outer membrane, matrix, inner membrane and inner membrane space. The components of the electron transport chain, namely the cytochrome proteins and ATP synthase, are arranged on the inner membrane to allow for the movement of protons between the inner membrane space and matrix in order to create ATP.

Example Question #106 : Cell Functions

Hows does the act of breathing relate to cellular respiration in humans and other mammals. 

Possible Answers:

With each breath, oxygen is taken in and used for cellular respiration while nitrogen is exhaled as a waste product.

With each breath, nitrogen is taken in and used for cellular respiration while carbon dioxide is exhaled as a waste product.

With each breath, carbon dioxide is taken in and used for cellular respiration while oxygen is exhaled as a waste product.

There is no relationship between breathing an cellular respiration.

With each breath, oxygen is taken in and used for cellular respiration while carbon dioxide is exhaled as a waste product.

Correct answer:

With each breath, oxygen is taken in and used for cellular respiration while carbon dioxide is exhaled as a waste product.

Explanation:

The final electron acceptor of the electron transport chain in cellular respiration is oxygen. Additionally carbon dioxide is produced as a waste product during the citric acid cycle phase of cellular respiration.

Example Question #102 : Cellular Respiration

How does a reducing agent function in cellular respiration?

Possible Answers:

None, reducing agents are not used in the cellular respiration pathway

Taking electrons as an electron receptor

Taking electrons as an electron donor

Giving electrons as an electron receptor

Giving electrons as an electron donor

Correct answer:

Giving electrons as an electron donor

Explanation:

A reducing agent works as an electron donor, so it is ultimately giving away electrons to another molecule and ultimately making that other molecule more negative in charge, or reduced in charge. Note that a reducing agent is itself oxidized. Also recall the mnemonic OIL RIG (Oxidation Is Loss of electrons, Reduction Is Gain of electrons).

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