Question 1

Which of the following best describes the function of a signal sequence in a newly synthesized protein?

Accepted Answer

It acts as a 'zip code' that directs the protein to its correct cellular destination.

Question 2

A protein destined for the mitochondria is synthesized in the cytosol. Which of the following is TRUE about its transport?

Accepted Answer

It is transported post-translationally and kept unfolded by chaperones during import.

Question 3

Which process is responsible for the insertion of membrane proteins into the endoplasmic reticulum (ER) membrane?

Accepted Answer

Cotranslational transport

Question 4

A mutation removes the ER signal sequence from a protein that is normally secreted. What is the most likely outcome?

Accepted Answer

The protein will remain in the cytosol and not be secreted.

Question 5

Which of the following best explains why chaperone proteins are necessary for mitochondrial protein import?

Accepted Answer

They keep the polypeptide unfolded so it can be threaded through the mitochondrial membrane channels.

Question 6

Which of the following is NOT a component of the endomembrane system?

Accepted Answer

Mitochondria

Question 7

A protein contains a nuclear localization signal (NLS). Where will this protein most likely be found after translation?

Accepted Answer

In the nucleus

Question 8

During which process does the ribosome become attached to the ER membrane?

Accepted Answer

When the growing polypeptide contains an ER signal sequence

Question 9

Which of the following best describes the fate of a protein with no signal sequence?

Accepted Answer

It remains in the cytosol.

Question 10

A researcher adds an ER signal sequence to a normally cytosolic protein. What is the most likely result?

Accepted Answer

The protein will be imported into the ER.

Question 11

Which of the following steps occurs FIRST in the synthesis and sorting of a secreted protein?

Accepted Answer

Initiation of translation on a free ribosome in the cytosol

Question 12

Which of the following is a key difference between co-translational and post-translational protein transport?

Accepted Answer

Co-translational transport occurs while the protein is being synthesized; post-translational transport occurs after synthesis is complete.

Question 13

A protein is found to be glycosylated and present on the plasma membrane. Through which organelles did it most likely pass?

Accepted Answer

ER → Golgi apparatus → plasma membrane

Question 14

Which of the following best explains the role of the nuclear pore complex?

Accepted Answer

It regulates the passage of molecules between the nucleus and cytoplasm.

Question 15

A patient has a genetic defect in the receptor that recognizes the nuclear localization signal (NLS). Which cellular process is most likely to be disrupted?

Accepted Answer

Import of proteins into the nucleus

Question 16

Which of the following is TRUE about the endomembrane system?

Accepted Answer

It includes the ER, Golgi apparatus, lysosomes, and vesicles.

Question 17

Which of the following best describes the fate of a lysosomal enzyme that fails to receive its proper targeting signal in the Golgi?

Accepted Answer

It may be secreted from the cell instead of being delivered to the lysosome.

Question 18

Which of the following is a real-world consequence of a defect in protein sorting within the endomembrane system?

Accepted Answer

Accumulation of undigested substrates in lysosomal storage diseases

Question 19

Which equation best represents the energy requirement for active transport of proteins through the nuclear pore complex?

Accepted Answer

$$ 	ext{ATP} ightarrow 	ext{ADP} + 	ext{P}_i + 	ext{energy} $$

Protein Sorting and Transport Inside the Eukaryotic Cell

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드