Question

1. Experiments have shown that the addition of the drug colchicine to cultured fibroblasts inhibits the movement of transport vesicles. Based on protein sorting/transport, the cytoskeleton, and the action of colchicine, explain why this result is observed.

2. Insulin is a protein that is secreted into the blood to regulate blood sugar levels. Describe the process of insulin production and secretion, including where it is translated, how it is modified and processed, and how it is ultimately secreted from the cell. Be sure to point out any organelles that are involved in insulin production, as well as any important features of the insulin protein structure, along with all modifications and processing steps that occur from its initial translation to its secretion to the outside of the cell.

Answer 1

The proteins which are synthesized on rough endoplasmic reticulum by ribosomes can follow below mentioned secretory pathway:

1RER - 2Golgi - 3Lyososome/plasma membrane - 4membrane protein - 5secretory protein.

Protein can be directed to any one of these location depending on signal sequence. Movement of protein from 1 to 2 or any one point to another is in the vesicle formed by budding.

Vesicle movement is conducted by the microtubules (cytoskeleton element) . Microtubule is made up of alpha beta tubulin heterodimer and is responsible for vesicle movement and protein sorting to it's respective location.

Colchicine is a drug which blocks the tubulin l. Hence, prevents the assembly and polulymerization of microtubules which will prevent the vesicular transport of protein. Due to this the proteins will not reach to their respective location where there action is required.