Endoplasmic Reticulum and Golgi Questions and Answers

Answer: A

Correct answer: ribosomes bound to its outer surface

The ribosomes are what make it rough, and they are there because the proteins they are making carry a signal sequence directing the whole complex to the membrane. Lipid synthesis, calcium storage and detoxification are functions of the *smooth* reticulum, so a cell’s balance between the two forms tells you what it does - a plasma cell is packed with rough, a steroid-secreting cell with smooth.

Answer: B

Proteins entering the lumen are folded, checked and modified before travelling onward. Those made on free ribosomes in the cytosol stay in the cytosol instead. The decision is therefore taken very early, as the chain first emerges.

Answer: C

It also stores calcium, and in liver cells it carries the enzymes that render drugs and toxins more soluble. Packaging is the work of the Golgi apparatus and breakdown that of the lysosome. Each compartment specialises, which is the point of dividing the cell up at all.

Answer: D

Pancreatic acinar cells and antibody-producing plasma cells are both packed with it, because every secreted protein must pass through its lumen. The amount present in a cell is a reliable clue to what that cell does for a living.

Answer: A

Both are true and the reason accounts for the abundance: the enzymes that modify foreign compounds reside in this membrane, and the smooth reticulum proliferates further when a person is exposed to such compounds repeatedly.

Answer: B

The short stretch of amino acids is recognised as the chain emerges from the ribosome and the whole assembly is docked at the reticulum. It is usually cut off once the protein is inside the lumen. The mature protein therefore carries no trace of the address that delivered it.

Answer: C

Without the sequence the ribosome finishes its work in the cytosol and the protein stays there. This is the basic sorting decision on which the whole secretory pathway depends. Everything downstream follows from that single early branch point.

Answer: D

An initial sugar tree is added in the lumen of the reticulum and is then trimmed and extended in the Golgi. The pattern of sugars ends up marking the protein's destination and its identity. Sugar patterns also help other cells recognise it at the surface.

Answer: A

Vesicles arrive at the cis face nearest the reticulum, and finished products leave from the trans face on the far side. The cisternae between the two carry out successive modifications in order. Each cisterna holds its own set of enzymes, so the sequence of changes is fixed.

Answer: B

The trans Golgi network sorts the finished material into vesicles bound for the plasma membrane, the lysosome or secretion. Direction of travel through the stack is one-way from cis to trans. Retrograde vesicles return enzymes but never carry cargo backwards.