Cell Biology II

Question 1

What is the contribution, in percentage, of proteins to the plasmalemma?

Answer 1

25-75%

Question 2

Beta-amyloid precursor protein is important in what (five) cellular processes?

Answer 2

1) Neuronal migration during development
2) Synaptic formation and repair
3) Cell signaling
4) Long-term potentiation
5) Cell adhesion

Question 3

What is the causative molecule involved in Creutzfeld-Jakob disease?

Answer 3

A variant prion protein

Question 4

What is the normal prion protein (PrP) involved in, normally?

Answer 4

Cell surface, glycosylated GPI anchor within lipid rafts

Question 5

What does the variant prion protein do in Creutzfeld-Jakob disease?

Answer 5

Crosslinks filaments that are resistant to proteolysis and accelerates formation of other variants of the same form

Question 6

Normal prion proteins are implicated in what cellular processes?

Answer 6

1) Neuroprotective against ischemia
2) Control Circadian rhythms
3) Serve to organize myelin sheath

Question 7

What do carrier proteins do?

Answer 7

Transport one or two chemicals in one direction, or two molecules in opposite directions without energy expenditure

Question 8

What are protein pumps?

Answer 8

Transport proteins requiring the direct expenditure of energy

Question 9

What does the Na/K pump do?

Answer 9

1) Cleaves ATP to transport three Na out of the cell and two K into the cell
2) Functions to regulate intracellular volume

Question 10

What does digoxin do?

Answer 10

Partially inhibits Na/K pump, leading to decreased activity of Ca/Na transporter. Result is an increase in sarcoplasmic [Ca]

Question 11

What are multidrug resistant transporters (MDRs)?

Answer 11

Subfamily of primary transporter proteins that are ATPases

Question 12

Where is MDR-1 expressed?

Answer 12

1) Kidney
2) Intestine
3) Liver
4) BBB

Question 13

What does overexpression of MDR cause?

Answer 13

Causes some cancer cells to become resistant to cytotoxic drugs

Question 14

How is MDR-1 overexpression combatted pharmacologically?

Answer 14

1) RNA interference

2) Pharmacological inhibitors

Question 15

What does MDR-2 transport?

Answer 15

Direct bilirubin

Question 16

Which transporter is responsible for direct bilirubin?

Answer 16

MDR-2

Question 17

Which protein is defective in Dubin-Johnson Syndrome?

Answer 17

MDR-2

Question 18

A defect in MDR-2 leads to what disease?

Answer 18

Dubin-Johnson Syndrome

Question 19

Where is MDR-3 expressed?

Answer 19

Liver

Question 20

What is the function of MDR-3?

Answer 20

Flippase of phosphatidylcholine - flips it to the the outer canalicular membrane of hepatocytes so that it may be excreted into bile

Question 21

What are aquaporins?

Answer 21

Protein channels for water

Question 22

What are the protein channels for water called?

Answer 22

Aquaporins

Question 23

How many isoforms of aquaporins are there?

Answer 23

12

Question 24

Aquaporin-2 is expressed by what type of cell?

Answer 24

Renal collecting tubule cells

Question 25

Renal collecting tubule cells express what protein channel, specifically?

Answer 25

Aquaporin-2

Question 26

What induces translocation of aquaporin receptors to the plasma membrane of collecting tubule cells?

Answer 26

Vasopressin

Question 27

What does the translocation of aquaporin receptors to the plasma membrane of collecting tubule cells do to water reabsorption across their apical domain?

Answer 27

Increases reabsorption

Question 28

Nephrogenic diabetes insipidus results from mutation of both ________ genes

Answer 28

Aquaporin-2

Question 29

Mutations in both genes of aquaporin-2 results in what disease?

Answer 29

Nephrogenic diabetes insipidus

Question 30

What kind of channel is CFTR?

Answer 30

Chloride channel

Question 31

What does CFTR regulate in addition to chloride?

Answer 31

Na and HCO3-

Question 32

Na and HCO3- is regulated by what channel?

Answer 32

CFTR

Question 33

Where are glycolipids found, exclusively?

Answer 33

Noncytosolic lipid monolayer (also found in some intracellular membranes)

Question 34

What glycolipid serves as a receptor for cholera toxin?

Answer 34

Ganglioside Gm1

Question 35

Ganglioside Gm1 serves as a receptor what what toxin?

Answer 35

Cholera toxin

Question 36

What does cholera toxin do once it binds to ganglioside Gm1 receptor?

Answer 36

Ramps up synthesis of cAMP, leading to efflux of Na and water into intestinal lumen

Question 37

Carbohydrates in the plasmalemma have what charge?

Answer 37

Negative

Question 38

What are the five pathways for endocytosis?

Answer 38

1) Macropinocytosis 2) Clathrin-mediated endocytosis 3) Non-coated-mediated endocytosis 4) Caveolae-mediated endocytosis (Simian virus 40) 5) Phagocytosis

Question 39

Where does macropinocytosis occur?

Answer 39

Thyroid cells as they take up thyroglobulin and dendritic cells for immune surveillance

Question 40

Macropinocytosis relies on what type of cytoskeletal element?

Answer 40

Actin

Question 41

Is macropinocytosis specific or nonspecific for its substrate?

Answer 41

Nonspecific

Question 42

What molecule is required to pinch off the vesicle in clathrin-mediated endocytosis?

Answer 42

Dynamin (GTPase)

Question 43

Can clathrin-mediated endocytosis be mediated by receptors?

Answer 43

Yes

Question 44

What are two examples of receptor-mediated clathrin-mediated endocytosis?

Answer 44

1) Cholesterol (in LDL form) | 2) Protein hormones

Question 45

Where are cargo receptors located in clathrin-mediated endocytosis?

Answer 45

Coated pits

Question 46

What molecule associates with the intracellular portion of the cargo receptor in clathrin-mediated endocytosis?

Answer 46

Adaptin

Question 47

What is the role of adaptin in clathrin-mediated endocytosis?

Answer 47

Associates with the intracellular portion of the cargo receptor

Question 48

What condition occurs when there is a decrease or defect in LDL receptors?

Answer 48

Atherosclerosis

Question 49

Recycling of synaptic vesicles is performed by what type of endocytosis?

Answer 49

Clathrin-mediated endocytosis

Question 50

Cholera and Shiga toxins enter the cell via what endocytotic mechanism?

Answer 50

Non-coated-mediated endocytosis

Question 51

Is phagocytosis receptor-mediated?

Answer 51

Yes, generally (zipper-mediated)

Question 52

Phagocytosis is dependent on what type of cytoskeletal component?

Answer 52

Actin

Question 53

Does phagocytosis require clathrin?

Answer 53

No

Question 54

What do phagosomes fuse with?

Answer 54

Lysosomes