Question 1

Which of the following statements best describes the targeting signal required for nuclear-encoded mitochondrial matrix proteins?

Accepted Answer

An N-terminal amphipathic alpha-helix with positively charged amino acids, necessary and sufficient for import.

Question 2

During ATP synthesis in mitochondria, which equation best represents the net reaction catalyzed by ATP synthase?

Accepted Answer

$$ \mathrm{ADP} + \mathrm{P}_i \rightarrow \mathrm{ATP} + \mathrm{H}_2\mathrm{O} $$

Question 3

A patient with Zellweger syndrome accumulates very long chain fatty acids in their cells. Which defect is most likely responsible for this phenotype?

Accepted Answer

A defect in the Pex5 receptor, leading to failure of peroxisomal matrix protein import.

Question 4

Which of the following is TRUE regarding the import of proteins into peroxisomes?

Accepted Answer

Proteins are imported post-translationally in a fully folded state and the targeting signal is NOT cleaved.

Question 5

Which organelle uses a proton gradient across the thylakoid membrane to drive ATP synthesis?

Accepted Answer

Chloroplast

Question 6

What is the primary function of the TOM and TIM complexes in mitochondria?

Accepted Answer

To facilitate the import of nuclear-encoded proteins across the outer and inner mitochondrial membranes.

Question 7

Which of the following best explains why mitochondria and chloroplasts have their own genomes?

Accepted Answer

They originated from endosymbiotic bacteria, retaining some genetic material.

Question 8

A protein destined for the mitochondrial inner membrane is synthesized in the cytosol. Which sequence of events is most likely for its import?

Accepted Answer

It is imported via the TOM complex, then the TIM complex, and secondary signals direct it to the inner membrane.

Question 9

Which of the following is a key difference between protein import into mitochondria and peroxisomes?

Accepted Answer

Peroxisomal proteins are imported in a folded state, while mitochondrial proteins are imported unfolded.

Question 10

Which equation best represents the net ATP yield from complete oxidation of one glucose molecule in mitochondria?

Accepted Answer

$$ \mathrm{Glucose} + 6\,\mathrm{O}_2 \rightarrow 6\,\mathrm{CO}_2 + 6\,\mathrm{H}_2\mathrm{O} + 30\,\mathrm{ATP} $$

Question 11

Which of the following statements about the targeting of proteins to chloroplasts is CORRECT?

Accepted Answer

Proteins use an N-terminal amphipathic helix as a stroma targeting signal and are imported post-translationally.

Question 12

Which of the following is a function of peroxisomes?

Accepted Answer

Beta-oxidation of very long chain fatty acids and production of $$ \mathrm{H}_2\mathrm{O}_2 .$$

Question 13

Which protein import pathway involves the recognition of an N-terminal amphipathic helix by a receptor on the organelle's outer membrane?

Accepted Answer

Mitochondrial matrix protein import

Question 14

Which of the following statements about mitochondrial DNA is TRUE?

Accepted Answer

Mitochondrial DNA encodes a small subset of proteins, with most mitochondrial proteins encoded by nuclear DNA.

Question 15

Which of the following best describes the role of cytosolic chaperones in mitochondrial protein import?

Accepted Answer

They help keep the protein unfolded prior to import.

Question 16

Which of the following is a key feature of the ATP exchanger in the mitochondrial inner membrane?

Accepted Answer

It uses a voltage gradient to exchange ATP and ADP across the membrane.

Question 17

Which of the following is TRUE regarding the targeting of proteins to the thylakoid membrane in chloroplasts?

Accepted Answer

Proteins require a thylakoid targeting sequence and may use one of several bacterial-like transport mechanisms.

Question 18

Which of the following statements about the maintenance and dynamics of mitochondria is CORRECT?

Accepted Answer

Mitochondria undergo fission and fusion, allowing them to change shape and number within the cell.

Protein Targeting to Mitochondria, Chloroplasts, and Peroxisomes

Study Guide - Practice Questions