Q: NADH and FADH$_2$ donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation. As electrons are passed down the chain, protons ($H^+$) are pumped across the mitochondrial membrane. Through which components do the protons move to generate ATP?

$\text{mitochondrial matrix, intermembrane space, ATP synthase}$

Question 1

The optimal temperature for most human enzymes is about $37^\circ C$. If the temperature is raised to $60^\circ C$, what is the most likely effect on enzyme activity?

Accepted Answer

The enzyme will denature due to the high heat.

Question 2

A molecule binds to an enzyme at a site other than the active site, causing a change in the enzyme's shape and reducing its activity. What type of inhibition is this?

Accepted Answer

Noncompetitive inhibition

Question 3

During glycolysis, glucose ($C_6H_{12}O_6$) is converted into two molecules of pyruvate ($C_3H_4O_3$). Which of the following best describes the overall process?

Accepted Answer

Glycolysis is a catabolic pathway because glucose is oxidized and energy is released through substrate-level phosphorylation.

Question 4

NADH and FADH$_2$ donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation. As electrons are passed down the chain, protons ($H^+$) are pumped across the mitochondrial membrane. Through which components do the protons move to generate ATP?

Accepted Answer

$	ext{mitochondrial matrix, intermembrane space, ATP synthase}$

Question 5

A product of a metabolic pathway inhibits an earlier enzyme in the same pathway by binding to a site other than the active site. What is this phenomenon called?

Accepted Answer

Feedback inhibition

Question 6

Which stage of cellular respiration occurs in the cytoplasm?

Accepted Answer

Glycolysis

Question 7

A scientist grows yeast in two different environments: one with oxygen and one without. Which culture will have a higher rate of ATP production and why?

Accepted Answer

The culture with oxygen, because it can perform cellular respiration, which is more efficient than fermentation.

Question 8

In the citric acid cycle, a mutation in pyruvate dehydrogenase prevents the conversion of pyruvate to acetyl CoA. What will happen to the concentration of citrate in the cycle?

Accepted Answer

The concentration of citrate will decrease because acetyl CoA will not be produced to combine with oxaloacetate.

Question 9

Which of the following statements about the Calvin Cycle is true?

Accepted Answer

The product of 3 cycles is the net synthesis of 1 G3P molecule.

Question 10

During glycolysis and the citric acid cycle, ATP is formed by substrate-level phosphorylation. During oxidative phosphorylation, ATP is formed by which process?

Accepted Answer

Chemiosmosis (proton-motive force)

Question 11

In photosynthesis, the linear electron flow requires light. Why is light necessary for this process?

Accepted Answer

A photon is needed to pass through pigment molecules and excite electrons in $P_{680}$ so they can continue through the rest of the system.

Question 12

A scientist removes $CO_2$ from the environment of a plant in a lab experiment. What would be the result in terms of the Calvin Cycle?

Accepted Answer

No G3P would be produced, because $CO_2$ is required for the Calvin Cycle to release one G3P molecule after three turns.

Question 13

Dehydroepiandrosterone (DHEA) is released into the bloodstream by the adrenal cortex and acts on distant target cells. What type of cell signaling is this?

Accepted Answer

Endocrine signaling

Question 14

A person with type 1 diabetes cannot produce insulin. What is the most likely result for glucose uptake in their cells?

Accepted Answer

Glucose will not be able to enter the cell, since the phosphorylation cascade will not occur without insulin and the GLUT4 protein will not be produced.

Question 15

A study finds that a ligand produces a cellular response in vitro but not in vivo. What is the most likely explanation?

Accepted Answer

The ligand is insoluble in the phospholipid bilayer and cannot enter the cell to participate in intracellular signaling.

Question 16

What is the immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation?

Accepted Answer

The $H^+$ concentration gradient across the membrane holding ATP synthase

Question 17

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

Accepted Answer

Glycolysis

Question 18

What is the final electron acceptor of the electron transport chain in aerobic oxidative phosphorylation?

Accepted Answer

Oxygen ($O_2$)

Question 19

In the mitochondria, exergonic redox reactions:

Accepted Answer

Provide the energy that establishes the proton gradient

Cellular Respiration, Enzyme Function, and Cell Signaling: Study Notes

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