Lecture 6 - Cell Membrane

Question 1

RBC membrane versus myelin membrane

Answer 1

RBC has more protein than lipids

Myelin has more fat than protein

Question 2

Disease:

• Autoimmune disease with production of antibodies directed against specific phospholipids (the targeted one varies between patients).
• Common symptom is formation of thrombosis.
• Usually onset is in early to mid-adulthood.
• Relatively high incidence. 20% of stroke patients younger than 50 have APS which is the cause of the stroke.

Answer 2

Antiphospholipid Syndrome (APS)

Question 3

Membrane proteins that help start endocytosis

Answer 3

Clathrin or caveolin

Question 4

How does cholesterol get into cell?

Answer 4

LDL low density lipoportein

Question 5

3 types of proteins on membrane

Answer 5

Integral proteins (Transmembrane proteins)
Peripheral proteins (attached to integral or freefloating)
Lipid-anchored proteins (attached to lipid tails covalently)

Question 6

Blood type is mainly due to which substance

Answer 6

Glycolipids

Question 7

Determinants of diffusion rate across lipid bilayer

Answer 7

• Hydrophobicity of molecule
• Surface area of membrane.
• Technically, thickness of membrane. However, it doesn’t vary much between cell types. Its thickness is 7.5-10nm

Question 8

Fick’s law equation J =PxDelta(X)

meaning of J, P, and DeltaX

Answer 8

J=Flux,he amount of substance X passing through a certain cross-sectional area in a certain amount of time, i.e. diffusion rate.

P=Permeability of coefficien

DeltaX= concentration difference (i.e. gradient) of X across the membrane

Question 9

3 types of membrane transport systems

Answer 9

• Pores
• Gated Channels
• Carriers

Question 10

Examples of active transport (against concentration gradient)

Answer 10

• Na-K pump (Primary)

- Sodium-glucose secondary active transporter (SGLT) (Secondary)

Question 11

How does probenecid treat gout?

Answer 11

Gout is caused by an elevated level of uric acid in the plasma. In the kidney there are organic anion transporters that reabsorb uric acid from filterate. Probenecid competes with uric acid to block its reabsorption

Question 12

Saturation and diabetes, how does this cause glucose in urine?

Answer 12

As fluid flows down nephrons (functional unit of kidney), glucose is reabsorbed. In diabetes, the amount of glucose exceeds capacity of transporters and therefore some appears in the urine.