Comprehension L03-L04

Question 1

Does increasing the percentage of saturated fatty acids in a membrane increase or decrease the membrane’s fluidity?

Answer 1

Decrease

Question 2

What 3 things affect transition temperature (fluidity) of a membrane?

Answer 2

1. FAC saturation
2. Cholesterol content
3. FAC length

Question 3

How does FAC saturation affect fluidity of a membrane?

Answer 3

Saturated fatty acids are straight flexible rods, but Cis-unsaturated FA bend at the sites of double bonds, which increases membrane fluidity

Question 4

How does cholesterol content in a membrane affect fluidity?

Answer 4

Hydrophobic rings impair movement of the phospholipid FAT
Eliminates a sharp transition temp and creates intermediate fluidity

Question 5

How does FAC length affect fluidity?

Answer 5

Shorter FAC: fewer VDW interactions
which means less energy needed to break them apart

Question 6

Why is a balance between membrane fluidity/rigidity important?

Answer 6

• Maintaining organization and support
• Enabling interactions
• Membrane assembly/cell growth/division
• Cell movement, secretion, endocytosis

Question 7

What 3 things happen to a membrane in response to colder temperatures?

Answer 7

1. desaturate single bonds in FAC to double bonds (desaturase)
2. Reshuffle chains bw phospholipids to create those with two unsaturated FA
3. synthesizes more FA with unsaturated bonds and shortened chain lengths

Question 8

What are the three types of membrane proteins?

Answer 8

Integral proteines
peripheral proteins
lipid anchored proteins

Question 9

What are integral proteins?

Answer 9

Proteins that are permanently anchored to, or are a part of the membrane.
Include transmembrane proteins

Question 10

What are characteristics of transmembrane proteins?

Answer 10

-Act as receptors, channels, or roles in electron transport
-Amphipathic

Question 11

How are peripheral membrane proteins associated to the membrane?

Answer 11

Weak, non covalent bonds (ionic, hydrogen bonds)

Question 12

Are peripheral membrane proteins hydrophobic or hydrophilic?

Answer 12

Hydrophobic

Question 13

What are the roles of peripheral membrane proteins (PMP)?

Answer 13

Signal transduction
mechanical support for the membrane
anchor for IMP
Enzymes

Question 14

What is the major component on the internal surface of the membrane on a PMP red blood cell?

Answer 14

Spectrin

Question 15

What are the features of a Lipid-anchored protein?

Answer 15

Outside the bilayer on either the extracellular or cytoplasmic side
Covalently linked to a lipid molecule in then bilayer

Question 16

What is a GPI-anchored protein?

Answer 16

• Proteins attached to the membrane by an oligosaccharide
• Glycosyl-PhoshatidylInositol linkage
• Roles in cell adhesion and as receptors

Question 17

How can phospholipids move around a membrane?

Answer 17

Laterally (easily) and by transverse diffusion (restricted)

Question 18

What things can penetrate the lipid bilayer?

Answer 18

Small inorganic solutes, such as O2, CO2, and H2O
Solutes with high lipid solubility

Question 19

What things cannot penetrate the lipid bilayer?

Answer 19

Ions and polar organic solutes
Anything too large

Question 20

Hypertonic cell:
Hypotonic cell:
Isotonic cell:

Answer 20

Hyper: higher concentration outside cell
Hypo: lower concentration outside cell
Iso: equal concentration

Question 21

What are voltage gated ion channels?

Answer 21

Open/closed depends on the diff in ionic charge on either side of membrane

Question 22

What are ligand gated ion channels?

Answer 22

• Open/Closed depends on the binding of a specific molecule (ligand)
• The ligand is usually not that solute that is passing through the channel

Question 23

What are mechano-gated ion channels?

Answer 23

Open/closed depends on mechanical forces