ER, Trafficking, Co-Translational Import

Question 1

Functions of smooth ER (SER)

Answer 1

• Lipid synthesis
• Production of steroid hormones
• Detoxification of foreign compounds
• Sequestration of calcium ions

Question 2

Functions of rough ER (RER)

Answer 2

• Synthesis of phospholipids
• glycosylation: Adding carb chains to proteins
• Protein folding with molecular chaperones
• Protein synthesis and transport

Question 3

Protein translation sites [2]

Answer 3

1) Free ribosomes
2) ER- Associated Ribosomes

Question 4

What is cotranslational import

Answer 4

Process by which a protein is synthesized and imported to the ER

Question 5

Steps to cotranslational import (5)

Answer 5

1) Signal sequence targets ribosome to ER
2) Signal Recognition Particle (SRP) binds to sequence and stops translation
3) SRP docks at ER receptor
4) Protein synthesis resumes, polypeptide enters ER
5) Signal peptide cleaved

Question 6

Mitochondrial protein targeting

Answer 6

1) protein synthesized on free ribosome
2) Transport relies on the TOM complex

Question 7

After protein is synthesized in the RER, where can it go?

Answer 7

1) Retained in the ER lumen
2) Sent to the endomembrane system or out of the cell

Question 8

After protein is synthesized by a free ribosome, where can it go? [4]

Answer 8

1) Nucleus
2) Mitochondria
3) Chloroplasts
4) Peroxisomes