Membrane Structure Flashcards Preview

Molecules to Medicine III > Membrane Structure > Flashcards

Flashcards in Membrane Structure Deck (18)
1

What are the molecular components of the membrane?

lipids (lipid bilayer)
carbohydrates (usually on extracellular domains of lipids or proteins)
proteins (30% of encoded proteins are membrane-associated

2

Explain the concept of membrane fluidity

phospholipids diffuse rapidly (10^7times/sec)
- several mm/s @ 37C
- do not spontaneously flip-flop (need ATP driven flipase)

3

What are the parts of a phospholipid?

Diglyceride
Phosphate group
Choline

4

What are the parts of a sphingolipid?

long
charged
have amine
- may have sugar

5

What are the parts of a cholesterol?

Polar hydroxyl group
Rigid steroid ring group
Hydrocarbon tail

6

How are membrane bilayers asymmetric?

carbohydrates on extracellular side
- non-uniform distribution of lipids/ proteins
more - phosphipids (PS, PE, PI) on inside of membrane
PC, sphingomyelin, glycolipids on outside

7

What are the different ways proteins can associate with membranes?

Transmembrane (x 1, x>1, cylinder)
Intra/extracellular (self-anchored, lipid anchored, oligosaccaride linked, monocovalent interaction with another protein)

8

How is cholesterol synthesis regulated?

SYNTHESIS
~30 enzymes
Statins: blick first step- HMGCoAreductase

UPTAKE
-negative feedback loop
-depends on LDLR
-enough through diet -> decrease synthesis

BOTH
- SREBP: regs LDLR and all synth enzymes

9

What is the function of proteins in the membrane?

Control the movement of molecules between the inside and outside of the cell

10

What does membrane fluidity depend on?

composition and temperature

11

What are the characteristics of phospholipids? Examples?

amphipathic (hydrophilic & hydrophobic)
Phosophatidylethanolamine (PE)
Phosphastidylcholine (PC)
Phosphatidylserine (PS)
Phosphatidyllinositol (PI)
- derived from glycerol

12

How do cholesterols interact with other lipids?

interaction of ring and other lipids's tails immobilize - decreases fluidity

tails are straightened by cholesterol - > membrane thickness

13

Where does cholesterol come from?

ingestion/ uptake
synthesis by the liver

14

What is SCAP?

SREBP cleavage activating protein

15

What is Insig

cholesterol regulating protein

16

What happens when cholesterol is high?

Insig binds SCAP-> blocks signaling

17

What happens when cholesterol is low?

SCAP binds SREBP -> goes to golgi -> bHLH released from SREBPby RIP (regulated intramembrane proteolysis) ->cleaved by S1P & S2P-> bHLH moves into nucleus -> binds promoters, activates genes to produce LDLRs & increase enzymes involved in cellular synthesis of cholesterol

18

How do some bacteria disrupt the cell membrane?

secrete toxins that create pores -> rupture membranes (staphlococcus aureus, listeria monocytogenes)