Chapter 27 Self-test questions

. Proteins directed to which of the following organelles are synthesized by ribosomes attached to the rough endoplasmic reticulum?

Lysosomes.

Mitochondria.

Nucleus.

Peroxisomes.

. A C-terminal peptide sequence of four amino acids, Lys–Asp–Glu–Leu (KDEL) directs proteins to which of the following organelles?

Endoplasmic reticulum.

Mitochondria.

Nucleus.

Peroxisomes.

. What directs vesicles carrying proteins modified in the Golgi cisternae to their appropriate place in the cell?

A sequence of amino acids within the proteins.

A specific carbohydrate bound to the proteins.

Coatomer or clathrin proteins coating the vesicle.

Complementary SNARE proteins on the vesicle and its target organelle.

. In what form do proteins cross the mitochondrial membranes?

Bound to an importin protein via a signal sequence.

In fully folded form.

In unfolded extended form attached to Hsp 70 chaperones.

In unfolded extended form without chaperones.

. How do proteins enter peroxisomes?

Folded, using a C-terminal or internal signal sequence.

Folded, using an N-terminal or internal signal sequence.

Unfolded, using a C-terminal or internal signal sequence.

Unfolded, using an N-terminal or internal signal sequence.

. Which of the following is a common feature of Nuclear Localization Signals?

They are rich in acidic amino acid residues and are located at the C-terminus of the protein.

They are rich in basic amino acid residues and are located at the C-terminus of the protein.

They are rich in acidic amino acid residues and may be located anywhere in the protein sequence.

They are rich in basic amino acid residues and may be located anywhere in the protein sequence.

. What constitutes the driving force for transport of proteins into and out of the nucleus?

ATP hydrolysis within the cytosol.

ATP hydrolysis within the nucleus.

GTP hydrolysis within the cytosol.

GTP hydrolysis within the nucleus.

. Proteins destined for which of the following locations are synthesized by ribosomes attached to the rough endoplasmic reticulum? Please select all that apply.

Nucleus.

Mitochondrial matrix.

Lysosomes.

Plasma membrane.

Peroxisomes.

Secretory vesicles.

. Which of the following signals directs a protein to the lysosomes?

A lys-asp-glu- leu (KDEL) sequence in the protein.

Dolichol phosphate.

Attached carbohydrate with terminal mannose-6-phosphate.

Attached carbohydrate with terminal mannose.

. Vesicles leaving the trans Golgi carry on their surfaces a protein which targets them to the appropriate organelle. This protein is:

t-SNARE.

Coatomer.

v-SNARE.

Clathrin.

. Where do proteins inserted into the inner mitochondrial membrane originate?

In the cytosol inserted using outer and inner membrane translocases (TOMs and TIMs) and in the matrix inserted using TIMs.

In the cytosol, inserted using outer membrane translocases (TOMs) and inner membrane translocases (TIMs).

In the matrix inserted using inner membrane translocases (TIMs).

. Which of the following is transported out of the nucleus across the nuclear pore?

Ribosomes.

Ribosomal RNA.

Ribosomal proteins.

Histones.

. In what ways can signal pathways activate transcription factors so that they are transported into the nucleus? Please select all that apply.

Detachment of the transcription factor from a complexing protein can unmask a nuclear localisation signal.

Phosphorylation of importin protein increases its binding affinity for transcription factors.

Phosphorylation of the transcription factor can increase its importin binding affinity.

Dephosphorylation of the transcription factor can increase its importin binding affinity.

Chapter 27 Self-test questions

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