Q: Which equation best represents the hydrolysis of GTP by Ran-GAP during nuclear transport?

$$\mathrm{Ran\text{-}GTP} \rightarrow \mathrm{Ran\text{-}GDP} + \mathrm{P_i}$$

Question 1

Which of the following best explains why eukaryotic cells require membrane-enclosed organelles?

Accepted Answer

To isolate incompatible chemical reactions and allow specialized functions within compartments.

Question 2

Which organelles are considered semi-autonomous and are thought to have evolved from ancient bacteria via endosymbiosis?

Accepted Answer

Mitochondria and chloroplasts

Question 3

A protein destined for the mitochondria is synthesized in the cytosol. What feature ensures its correct delivery?

Accepted Answer

A specific amino acid signal sequence at the N-terminus recognized by mitochondrial translocators

Question 4

Which of the following statements about nuclear pore complexes is TRUE?

Accepted Answer

They are composed of a meshwork of proteins that regulate the passage of macromolecules.

Question 5

A mutation alters the nuclear localization signal (NLS) of a protein. What is the most likely consequence?

Accepted Answer

The protein will be retained in the cytosol and fail to enter the nucleus.

Question 6

Which process is directly powered by GTP hydrolysis in nuclear transport?

Accepted Answer

The dissociation of import receptors from their cargo inside the nucleus

Question 7

During cell division, the nuclear envelope breaks down. Why do nuclear proteins retain their localization signals?

Accepted Answer

To allow them to re-enter the nucleus once it reforms.

Question 8

Which of the following is a typical signal sequence for import into the nucleus?

Accepted Answer

A stretch of positively charged amino acids such as lysine and arginine

Question 9

Differential centrifugation is used to separate cellular components. Which component will pellet first at the lowest speed?

Accepted Answer

Nuclei

Question 10

A protein is synthesized on a free ribosome in the cytosol. What determines its final destination within the cell?

Accepted Answer

The presence and type of signal sequence within its amino acid chain

Question 11

Which equation best represents the hydrolysis of GTP by Ran-GAP during nuclear transport?

Accepted Answer

$$\mathrm{Ran	ext{-}GTP} ightarrow \mathrm{Ran	ext{-}GDP} + \mathrm{P_i}$$

Question 12

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

Accepted Answer

Mitochondria

Question 13

A protein with the signal sequence '-Ser-Lys-Leu-' at its C-terminus is most likely targeted to which organelle?

Accepted Answer

Peroxisome

Question 14

Which of the following best describes the role of nuclear import receptors?

Accepted Answer

They recognize nuclear localization signals and facilitate transport of proteins through nuclear pores.

Question 15

Which pathway is used for the transport of proteins from the ER to the Golgi apparatus?

Accepted Answer

Vesicular transport

Question 16

Which of the following statements about protein sorting is CORRECT?

Accepted Answer

Proteins destined for mitochondria and chloroplasts are synthesized on free ribosomes in the cytosol.

Question 17

Which of the following is a consequence of a defective Ran-GEF in the nucleus?

Accepted Answer

Ran-GTP levels in the nucleus will decrease, impairing nuclear import.

Question 18

Which of the following best describes the difference between biomolecular condensates and membrane-enclosed organelles?

Accepted Answer

Biomolecular condensates are formed by noncovalent interactions and lack a surrounding membrane, while membrane-enclosed organelles are defined by a lipid bilayer.

Question 19

A protein is found in the lumen of the ER but lacks its retention signal. What is the most likely fate of this protein?

Accepted Answer

It will be exported from the ER and may be secreted from the cell.

Intracellular Compartments and Protein Transport

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