(L2) Clinical Relevance of Cell Membranes and Transport

Question 1

What is the cause of Niemann-Pick Disease?

L2 S11 LO1

Answer 1

Deficiency in acid sphingomyelniase (A-SMase)

Lysosomal enzyme that breaks down sphingomyelin into:

• ceramide
• phosphorylcholine

Deficiency results in build up in lysosomes in liver, spleen, CNS, and bone marrow.

Question 2

What are the clinical indications of Niemann-Pick disease?

L2 S11 LO1

Answer 2

-“cherry red spot” in eye (slide 14)

• hepatomegaly
• spleenomegaly
• neurological damage

Question 3

What is the significance of the membrane asymmetry of phosphatidylserine?

L2 S17 LO1

Answer 3

Normally found only in the inner leaflet of healthy cells.

Cells undergoing apoptosis present it on the outer leaflet as a signal for phagocytes.

Question 4

How can apoptotic cells be distinguished from necrotic cells under the microscope?

L2 S18

Answer 4

Propidium iodide can be absorbed into necrotic cells but not apoptotic cells.

Question 6

What is the molecular basis of ABO blood typing?

L2 S21-22 LO2

Answer 6

Variable carbohydrate structure of glycoproteins/lipids of the cell membrane of RBCs.

Question 7

What is the molecular basis of Rh typing?

L2 S24 LO2

Answer 7

Presence or absence of the D antigen.

Question 8

What is the cause of spur cell anemia?

L2 S30 LO3

Answer 8

Elevated cholesterol levels resulting in decreased membrane fluidity.

Results in hemolytic anemia (RBCs lyse when passing through capillaries.

Typically caused by liver dysfunction resulting in decreased cholesterol metabolism

Question 9

What are the cytologic indications of spur cell anemia?

L2 S30 LO3

Answer 9

Presence of RBCs with thorny projection; acanthocytes

Question 10

What is cystinuria?

L2 S33 LO4

Answer 10

Autosomal recessive, defect in transported for dimeric cystine.

Results in cystine crystals in the kidney.

Question 11

What is Hartnup disease?

L2 S35 LO4

Answer 11

Autosomal recessive defect in transporter for non-polar AAs (such as tryptophan)

Tryptophan required for producing of serotonin, melatonin, and niacin (NAD+).

Question 12

What are the clinical findings and exacerbating factors of Hartnup disease?

L2 S35 LO4

Answer 12

• cerebellar ataxia
• photodermatitis/photosensitivity

Triggered by sunlight and fever

Typically follows period of poor nutrition

Question 13

What are cardiotonic drugs and what do they do?

L2 S37-38 LO4

Answer 13

Ouabain and digoxin

Inhibit Na+/K+-ATPase of cardiomyocytes resulting in increase intracellular Na+

Increased Na+ impairs sodium calcium exchanger (NCX) resulting in increased Ca+

Increased Ca+ increases contractile force of cardiomyocytes

Question 14

What is the clinical significance of cardiotonic drugs?

L2 S38 LO4

Answer 14

Treatment of:

• CHF
• AFIB
• dysrhythmias

Question 15

How does cystic fibrosis relate to cell membranes?

L2 S41-42 LO4

Answer 15

Autosomal recessive defect in cystic fibrosis transmembrane conductance regulator (CFTR), a Cl- active transporter.

Results in increased Cl- of cells in airway creating thick mucous