The Endoplasmic Reticulum

Question 1

what is the endoplasmic reticulum?

Answer 1

a network of membranes in the cytoplasm

Question 2

ER is continuous with?

Answer 2

with the other (almost) membranes in the cell

Question 3

what are ER cisternae?

Answer 3

membrane bounded sacs

Question 4

what is the ER lumen?

Answer 4

internal space enclosed by the ER membranes

Question 5

Functions of the ER? (2)

Answer 5

1. enzymes associated with the ER are involved in synthesis of proteins for:
   - incorporation into the plasma membrane
   - organelles of the endomembrane system
   - export from the cell
2. lipid synthesis

Question 6

ER can be? (2)

Answer 6

1. rough

2. smooth

Question 7

Rough ER

• what makes it rough?
• what do the ribosomes do?
• free ribosomes?

Answer 7

• studded with ribosomes on the cytoplasmic side of the membrane
• ribosomes synthesize polypeptides that accumulate within the membrane or are transported across it to the lumen
• free ribosomes are not associated with the ER

Question 8

Smooth ER

• function? (2)
• sarcoplasmic reticulum has critical functions in?

Answer 8

• no role in protein synthesis, involved in the synthesis of lipids and steroids.
• inactivating and detoxifying potentially harmful substances
• sarcoplasmic reticulum has a critical function in contractions