Endoplasmic Reticulum

Question 1

endoplasmic reticulum etymology

Answer 1

“network within the cell”

Question 2

2 parts of ER

Answer 2

1. ER membrane

2. ER lumen

Question 3

ER membrane percentage of cell volume

Answer 3

50-90%

Question 4

ER lumen percentage of cell volume

Answer 4

15%

Question 5

2 types of ER

Answer 5

1. rough ER

2. smooth ER

Question 6

rough ER appearance

Answer 6

flattened sheets and vesicles

Question 7

smooth ER appearance

Answer 7

tubules and vesicles

Question 8

3 steps in isolation and purification of ER

Answer 8

1. homogenization
2. differential centrifugation
3. equilibrium centrifugation

Question 9

microsomes

Answer 9

chunks of ER

Question 10

2 functions of ER metabolism

Answer 10

1. glycogen breakdown in liver

2. drug metabolism in liver and other organs

Question 11

how does ER breakdown glycogen

Answer 11

enzyme in smooth ER produces glucose from glycogen

Question 12

how does ER breakdown drugs

Answer 12

membrane bound enzymes add -OH groups to toxic molecules to increase solubility

Question 13

morphine

Answer 13

strong and fast acting pain killer

Question 14

related drug to morphine

Answer 14

codeine

Question 15

codeine

Answer 15

is turned into morphine with CYP2D6 enzymes

Question 16

what is stored in the ER

Answer 16

Ca++

Question 17

sudden rise in cytosol [Ca++] triggers what?

Answer 17

gated passive transporters on cell membrane and ER membrane open

Question 18

what 2 things are synthesized in the ER

Answer 18

1. lipids

2. proteins

Question 19

2 types of lipids synthesized in ER

Answer 19

1. phospholipids

2. cholesterol

Question 20

where are phospholipids produced in the ER

Answer 20

on the outer face

Question 21

scramblases

Answer 21

equalize numbers of phospholipids in the 2 faces

Question 22

why are scramblases necessary

Answer 22

because phospholipids are only produced on the outer face

Question 23

flippases

Answer 23

establishes and maintains membrane asymmetry

Question 24

transport vesicles

Answer 24

deliver phospholipids to other organelles in the endomembrane system

Question 25

phospholipid exchange proteins

Answer 25

deliver phospholipids to organelles not in the endomembrane system like mitochondria

Question 26

what makes cytosol proteins

Answer 26

free ribosomes

Question 27

where are proteins for organelles made?

Answer 27

made in the cytosol and then sent to their organelle

Question 28

posttranslational transport

Answer 28

proteins for organelles are made in cytosol and sent to their organelle

Question 29

cotranslational transport

Answer 29

plasma membrane proteins are made in ER

Question 30

what prevents proteins from folding prematurely

Answer 30

BiP proteins shield hydrophobic regions from water

Question 31

2 other names for BiP

Answer 31

1. binding protein | 2. heat shock A5 protein

Question 32

what is required for making an export protein

Answer 32

an ER signal sequence

Question 33

stop-transfer sequence

Answer 33

NH3+ end of protein is in the lumen and COO- end is in the cytosol

Question 34

start-transfer sequence

Answer 34

NH3+ end is in the cytosol and COO- end is in the lumen

Question 35

N-terminus signal sequence

Answer 35

the polypeptide will not remain in the ER

Question 36

example of a protein produced in the ER

Answer 36

transferrin receptor

Question 37

transferrin receptor

Answer 37

imports iron into the cell via receptor mediated endocytosis

Question 38

glycosylated membrane proteins

Answer 38

membrane proteins with sugars attached

Question 39

core glycosylation

Answer 39

sugar groups are assembled and attached to a protein as one unit

Question 40

where does core glycosylation occur

Answer 40

in the ER lumen