2.5 c: cellular respiration quiz proctor...

1. Cyanide is introduced into a culture of cells and is observed binding to a mitochondrion, as

shown in the diagram below.

The following observations are made:

Cyanide binds to and inhibits an enzyme in the inner mitochondrial membrane.•

There is a decrease in water production in the inner mitochondrial membrane.•

Cyanide causes a build-up of NADH in the mitochondrial matrix.•

Which statement best explains where cyanide causes the initial disruption in an important

cellular process?

(A) Cyanide prevents the production of carbon dioxide by binding to the enzymes involved in the

citric acid cycle.

Distractor Rationale:

This answer suggests the student may understand that carbon dioxide is produced during

the citric acid cycle, but does not understand that cyanide primarily disrupts an enzyme in

the electron transport chain from accepting or donating electrons and does not disrupt the

citric acid cycle directly.

(B) Cyanide prevents enzymes from splitting glucose into smaller organic molecules during

substrate-level phosphorylation.

2.5 C: Cellular Respiration Quiz

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This answer suggests the student may understand that the splitting of glucose during

substrate-level phosphorylation involves enzymes and produces energy-rich molecules that

drive the electron transport chain, but does not understand that the splitting of glucose

occurs in the cytosol and is not affected by the presence of cyanide.

(C) Cyanide prevents enzymes in the inner membrane from allowing ions to move from areas of

lower pH to areas of higher pH.


This answer suggests the student may understand that ions move across the inner

membrane via the enzyme ATP synthase, from an area of high concentration and higher pH

to areas of low concentration and lower pH in the matrix, but does not understand that

cyanide primarily disrupts the electron transport chain by binding to enzymes that accept or

donate electrons along the electron transport chain, as evidenced by the decrease in water

production.

(D) Cyanide prevents the oxidation of energy-rich molecules by binding to enzymes that

facilitate movement of the electrons in the electron transport chain.

Rationale:

This answer suggests the student understands that the location of the electron transport

chain is in the inner mitochondrial membrane, and that cyanide binds to enzymes in the

electron transport chain, preventing them from accepting and donating electrons, evidenced

by the buildup of NADH and the lack of water, and also prevents the formation of the proton-

motive force needed to pump ions into the intermembrane space in order to create an

electrochemical gradient used to produce ATP.

Aligned to: LO 2.5 CA 2.5: Explain Energy Use, Storage & Capture


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2. The diagram below shows the pathway for the movement of electrons in a mitochondrion.

Which of the following describes the process in chloroplasts that is most similar to the process

shown in the diagram?

(A) the reduction of carbon dioxide into 3-carbon sugars in the stroma during the Calvin cycle


This answer suggests the student may understand that the reduction of carbon dioxide into

3-carbon sugars involves the transfer of electrons, but does not understand that electrons

are not transferred in a way that is similar to the movement of electrons down an

electrochemical gradient in the electron transport chain.

(B) the excitation of electrons in photosystem II on the thylakoid membrane during the light-

dependent reaction


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This answer suggests the student may understand that electrons are excited by light in

photosystem II, but does not understand that electrons are excited to higher energy levels

in photosystem II, rather than moving to lower energy levels as they move through the

electron transport chain.

(C) the movement of hydrogen ions from a high concentration inside of the thylakoid space to

the stroma via chemiosmosis


This answer suggests the student may understand that hydrogen ions move from the

thylakoid space to the stroma during chemiosmosis in chloroplasts, but does not

understand that the movement of hydrogen ions in the diagram is from regions of low

concentration to regions of high concentration (via energy released from the electron

transport chain), which produces the electrochemical gradient that is then used to drive the

production of ATP (when ions move back to the stroma from the thylakoid space).

(D) the oxidation of proteins on the thylakoid membrane during noncyclic photophosphorylation

to create an electrochemical gradient

Rationale:

This answer suggests the student understands that the electron transport chain on the

thylakoid membrane is similar to the electron transport chain on the inner mitochondrial

membrane, and that the energy released by the transfer of electrons through the electron

transport chain via redox reactions is used to pump protons across a membrane, which

produces an electrochemical gradient that provides energy for the production of ATP

(chemiosmosis).



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3. A root cutting is placed in a sealed container. The relative levels of carbon dioxide and oxygen

gas in the container are measured and recorded in millimeters of mercury (mmHg) every 6 hours

over the next 24 hours. The results are shown in the table below.

Which statement best explains the results shown in the table?

(A) The root cutting is undergoing anaerobic fermentation to generate energy because the low

oxygen levels prevent the root cutting from utilizing the citric acid cycle or oxidative

phosphorylation.


This answer suggests the student may understand that an organism undergoes fermentation

when oxygen levels are too low, but does not understand that oxygen is not used during

fermentation, and that the root cutting is undergoing cellular respiration, as evidenced by the

decreasing oxygen concentration and by the increasing carbon dioxide concentration.

(B) The root cutting is using the Calvin cycle to generate energy by consuming oxygen because

there is not enough light available to stimulate the movement of electrons to carry out the

light reactions.


This answer suggests the student may understand that the root cutting is consuming

oxygen, but does not understand that carbon dioxide (not oxygen) is used during the

Calvin cycle to produce sugar, and that the plant is undergoing cellular respiration, as

evidenced by the decreasing oxygen concentration and by the increasing carbon dioxide

concentration.

(C) The root cutting is undergoing aerobic cellular respiration because the root cutting is

generating carbon dioxide from organic molecules and is reducing oxygen to form water.


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Rationale:

This answer suggests the student understands that the root cutting is undergoing cellular

respiration, as evidenced by the decreasing oxygen concentration (oxygen is reduced to

form water in cellular respiration) and by the increasing carbon dioxide concentration

(carbon dioxide is generated from organic molecules during the citric acid [Krebs] cycle).

(D) The root cutting is undergoing photolysis in the light-dependent reactions because oxygen is

being split and combined with carbon to form carbon dioxide.


This answer suggests the student may understand that photolysis occurs during the light-

dependent reactions in photosynthesis, but does not understand that oxygen is not split

and is not combined with carbon to form carbon dioxide during photosynthesis, or that the

plant is undergoing cellular respiration, as evidenced by the decreasing oxygen

concentration and the increasing carbon dioxide concentration.


4. The diagram below shows how the nutrients triglycerides, glucose, and amino acids are

metabolized to generate ATP in a mitochondrion.


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Which statement best explains how the mitochondrion utilizes nutrients to generate ATP?

(A) Triglycerides are utilized to generate ATP only when the amount of FAD is greater than the

amount of NAD+.

Rationale:

This answer suggests the student may understand that the role of NAD+ and FAD in cellular

respiration is to carry electrons to the electron transport chain, but does not understand

that both of these molecules are reduced regardless of the type of nutrient being utilized.

(B) Excess fatty acids in the cytosol are used in the Krebs cycle only when supplies of glucose

and amino acids are too low to produce sufficient amounts of Acetyl-CoA.


This answer suggests the student may understand that excess nutrients are converted into

fatty acids in the cytosol, but does not understand that all nutrients are catabolized to

generate ATP simultaneously, or that proteins, carbohydrates, and fats can all be used as

sources to produce Acetyl CoA.

(C) Each type of nutrient is processed by a different pathway in the Krebs cycle, and the number

of electrons that can be used to generate ATP is controlled by each pathway.


This answer suggests the student may understand that nutrients are metabolized by

processes in the Krebs cycle, but does not understand that most of the nutrients are

metabolized into the same molecule, Acetyl-CoA, which is used to drive the Krebs cycle, or

that the amount of ATP generated depends on which enzyme (NAD+ or FAD) is used to

carry electrons to the electron transport chain.

(D) Glucose is utilized to generate ATP through substrate-level phosphorylation when oxygen

levels are too low to utilize triglycerides or amino acids via oxidative phosphorylation.


This answer suggests the student understands that cellular respiration of triglycerides and

amino acids requires oxygen in order to generate ATP, and that only glucose can continue

to be catabolized when oxygen is limited, which may result in more ATP generated from

glucose when blood oxygen levels are low.



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5. The diagram below shows the processes occurring in and around the inner mitochondrial

membrane.

Based on the diagram, which question best investigates a factor that affects the processes

shown?

(A) What effect will lowering the pH in the intermembrane space have on the proteins in the

inner mitochondrial membrane?

Rationale:

This answer suggests the student understands that H+ ions are being pumped into the

intermembrane space, which lowers the pH, and that lowering the pH in this space even

further may affect the structure and function (denaturing) of proteins in the membrane and

may prevent the proteins from pumping H+ ions or transferring electrons in the electron

transport chain.

(B) If oxygen gas is being converted into water in the mitochondrial matrix, will the contents of

the mitochondrial matrix become more polar as the processes occur?


This answer suggests the student may understand that water is a polar molecule, but does

not understand that the contents of the matrix already include a high concentration of water

and are, therefore, already polar.

(C) If water is generated in the mitochondrial matrix, will the mitochondrial matrix become

hypotonic to the intermembrane space as the processes occur?


This answer suggests the student may understand that a high concentration of water on one

side of a plasma membrane will make that area hypotonic to another side with a lower water

concentration, but does not understand that water can diffuse through plasma membranes

(via aquaporins), so a hypotonic environment will not be produced.


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(D) What effect will the movement of negatively charged ions through the inner mitochondrial

membrane have on the production of water?


This answer suggests the student may understand that the movement of electrons through

the electron transport chain results in the formation of water molecules, but does not

understand that the electrons are being passed from protein to protein through reduction-

oxidation reactions within the membrane, and that the electrons are not being passed within

the membrane itself.



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2.5 c: cellular respiration quiz proctor...

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