Question

Proteins are manufactured from the "blueprints" found on DNA. After they are translated, they are moved through a system of internal membranes before being distributed throughout the rest of the cell. At some point in this process, they are modified to their functional form.

• Describe the movement of proteins from their manufacturing point through this internal membrane system.
• In your own words, discuss the role of each of the following structures in the whole process: cell membrane, vesicles (at two points in the process), ribosomes, Golgi apparatus, and endoplasmc reticulum. Be sure to

Answer 1

Most proteins are translated in the rough endoplasmic reticulum. The roughness of this compartment seen in electron micrographs of cells is due to ribosomes. It is at the ribosomes where the amino acids are joined together and the proteins formed. Depending on the signal sequence, proteins might be retained in the ER or moved to the Golgi. The signal sequence is a short sequence of amino acids which control the movement of the proteins in the cell. Vesicles are responsible for moving nascent proteins from ER to the Golgi aparatus.The Golgi aparatus is where this post-translational modification goes on:the proteins are often cleaved by enzymes or have more chemical groups added on. Proteins then are moved to other places in the cell in vesicles (sensibly named transport vesicles). The proteins might go to lysosomes, peroxisomes or to the cell membrane. I hope this helps, more information can be found on Wikipedia:

http://en.wikipedia.org/wiki/Endoplasmic_Reticulum