Exam #1; Cell Biology II

Question 1

Peripheral Protein

Answer 1

• Attached to the extracellular side of the plasmalemma

- Can be removed w/ salt solution

Question 2

Integral Protein

Answer 2

Protein partially or fully embedded in the plasmalemma

Question 3

Transmembrane Protein

Answer 3

Proteins that extend through the entire thickness of the plasmalemma

Question 4

Beta-Amyloid Precursor Protein (B-APP)

Answer 4

• Integral transmembrane protein
• Abnormal cleavage forms Beta-Amyloid peptides that aggregate
• Protein aggregates are resistant to proteolysis and implicated in Alzheimer’s Disease

Question 5

Normal Function of B-APP

Answer 5

• Neuronal migration during development
• Synaptic formation & repair
• Cell signaling
• LTP (memory)
• Cell adhesion

Question 6

PrP

Answer 6

• Prion Protein
• GPI anchored protein
• GPI anchor is embedded in lipid rafts
• Mutation implicated in Creutzfeld-Jakob Disease

Question 7

Normal Function of PrP

Answer 7

• Neuroprotection against ischemia
• Control circadian rhythm
• Organization of myelin sheath

Question 8

What stain can be used to visualize Beta-Amyloid & PrP?

Answer 8

Congo Red

Question 9

What are the seven functions of proteins?

Answer 9

1) Receptors
2) Carriers/ Pumps/ Channels
3) Enzymes
4) Linker proteins for structural support
5) Antigens (cell id. tag)
6) Anchor cell to ECM
7) Intercellular junction complexes

Question 10

What does it mean that receptors are dynamic and not static?

Answer 10

• There is up & down regulation of receptors in response to ligand to maintain homeostasis
• Decrease Ligand: Increase Receptor
• Increase Ligand: Decrease Receptor

Question 11

How do pharmacologic agents act to produce a therapeutic effect?

Answer 11

As receptor agonists or antagonists

Question 12

What is the clinical relevance of estrogen receptor?

Answer 12

• Many breast cancers show an upregulation of estrogen receptors
• ER + breast cancer can be treated with Tamoxifen/ Hormone Therapy

Question 13

Transport Proteins

Answer 13

• Carriers

- Pumps

Question 14

Carriers

Answer 14

• Transports without direct expenditure of energy

Question 15

Pumps

Answer 15

• Transport with direct expenditure of energy

Question 16

Na+/K+ Pump

Answer 16

• 3 Na+ Out & 2 K+ In w/ ATP energy

- Regulates intracellular volume

Question 17

Digoxin

Answer 17

• Used to treat heart failure
• Partially inhibits Na+/K+ Pump, which leads to an increase in Na+ concentration in the cell
• Destroys the concentration gradient needed for the Ca++/Na+ transporter
• Increases sarcoplasmic Ca++
• Increased sarcoplasmic Ca++, increases cardiac contractility

Question 18

Ca++/Na+ Transporter

Answer 18

• 4 Na+ In & 1 Ca++ Out

-

Question 19

Secondary Active Transport

Answer 19

Coupling the movement of a molecule down its concentration gradient to the electrochemical gradient established by primary active transport i.e. a pump

Question 20

Na+ & Glucose Co-transport

Answer 20

• Example of secondary active transport
• Glucose & Na+ transported into the cell down concentration gradient
• Na+/K+ Pump uses ATP energy to established this concentration gradient

Question 21

Multi-drug Resistant Transporters

Answer 21

• Subfamily of primary transporter proteins that are ATPases
• Transport molecules out of the cell

Question 22

MDR-1

Answer 22

• Transports drugs out of the cell
• Overexpression can cause cancer cells to become resistant to cytotoxic drugs; they;re transported out of the cell too quickly to take effect

Question 23

MDR Treatment

Answer 23

• RNA interference: silencing the gene coding for the MDR transporter
• Pharmacologic Inhibition

Question 24

MDR-2

Answer 24

Transports conjugated bilirubin from the hepatocyte into bile canaliculus

Question 25

Dubin-Johnson Syndrome

Answer 25

Benign disorder caused by a mutation in ATP binding region of MDR-2

Question 26

Aquaporin

Answer 26

Protein channel for water

Question 27

Aquaporin-2

Answer 27

Expressed by renal collecting tubule for water reabsorption

Question 28

ADH & Vasopressin

Answer 28

• Cause translocation of aquaporin receptors into the plasma membrane of the renal collecting tubule cell
• Increase water reabsorption through the kidney

Question 29

CFTR

Answer 29

• Chloride channel implicated in cystic fibrosis that also regulates Na+ & HCO3-
• Causes salty sweat
• Dehydrated airway mucous leading to chronic airway infection

Question 30

Lactose Intolerance

Answer 30

• Decrease in lactase enzyme
• Lactose is not absorbed; rather, interacts with gut flora
• Causes gas, bloating, diarrhea

Question 31

Linker Protein

Answer 31

• Links plasma membrane to underlying cytoskeleton

Question 32

Dystroglycan

Answer 32

• Linker protein in skeletal muscle that links cytoskeleton to plasma membrane
• Binds Dystrophin, a protein of the cytoskeleton lacking is Muscular Dystrophy

Question 33

Glycolipid

Answer 33

Carbohydrate attached to lipid

Question 34

Glycoprotein

Answer 34

Carbohydrate attached to protein

Question 35

Ganglioside Gm1

Answer 35

• A glycolipid that serves as the receptor for cholera toxin

Question 36

Cholera Toxin Mechanism

Answer 36

• Binds Ganglioside Gm1
• Increases cAMP
• cAMP causes Cl- efflux from CFTR
• Cl- efflux causes Ha+ & HCO3- efflux
• Causes profound diarrhea

Question 37

What are the 5 pathways of endocytosis?

Answer 37

1) Macropinocytosis
2) Clathrin-Mediated Endocytosis
3) Non-coated-mediated endocytosis
4) Caveolae-mediated endocytosis
5) Phagocytosis

Question 38

Creutzfeld-Jakob Disease

Answer 38

• Prion Disease caused by conversion of PP into PrP

- “human mad cow disease”