Question

how do ribosomes and the endoplasmic reticulum interact during protein synthesis?
a. mrna comes from the endoplasmic reticulum and is translated by ribosomes into polypeptide chains.
b. ribosomes receive proteins from the endoplasmic reticulum and modify them for later use.
c. ribosomes attached to the endoplasmic reticulum make proteins that function when they are embedded in a membrane.
d. vesicles in ribosomes modify and fold proteins that are built in the endoplasmic reticulum.

Explanation:

• Option A: mRNA comes from the nucleus, not the endoplasmic reticulum. So this option is incorrect.
• Option B: Ribosomes make proteins, not receive them from the endoplasmic reticulum. The endoplasmic reticulum modifies proteins made by ribosomes. So this option is incorrect.
• Option C: Ribosomes attached to the rough endoplasmic reticulum (RER) synthesize proteins. These proteins are often membrane - bound or secreted proteins. For example, integral membrane proteins are synthesized by ribosomes on the RER. The RER provides a site for the proper folding and initial modification of these proteins. This option is correct.
• Option D: Vesicles are not in ribosomes. Vesicles are involved in transporting proteins from the endoplasmic reticulum to the Golgi apparatus. So this option is incorrect.

Answer:

C. Ribosomes attached to the endoplasmic reticulum make proteins that function when they are embedded in a membrane.