Question

(a) Brefeldin A is a drug that disrupts transport from the Endoplasmic Reticulum to the Golgi apparatus. What other organelles and membranes in an animal cell would be affected by this drug and why? I know that the answer is Golgi apparatus functions including sorting and packaging of transport vesicles, lysosomes, and plasma membrane composition. But I do not know the reason why.

(b) If you were using organelle-specific stains and found that a stain for the nuclear envelope lightly stained another organelle as well, what would that other compartment be and why? The answer is the endoplasmic reticulum, but please explain why.

Thank you!

Answer 1

a) Golgi apparatus is a collection of folded membranes and vesicles. The proteins which are synthesized inside the endoplasmic reticulum (ER) is packed into vesicles and is fused into golgi membrane. These proteins are further modified in golgi and is sent to its destination ( secretory pathway) via vesicles from Golgi. These vesicles can be lysosomes, or exosomes which secrete the proteins outside via exocytosis or the proteins which are destined to be in plasma membrane. So in the absence of vesicles from ER the Golgi apparatus collapses and fuses back into the ER, The transport of vesicles, lysosomes and plasma membrane protein transport are all stopped affecting the all these organelles.

b)ER is a collection of membraneous tubes ( cisternae) which are interconnected in the cell.  ER membrane is an extension of the outer nuclear membrane. So when the nuclear envelope is stained then it will stain ER membrane too.