Lecture 7: Overview Of Membrane Structure

Question 0

Are membranes held together by covalent interactions?

Answer 0

No

Question 1

Which functional groups allow a cell to be identified by its membrane makeup?

Answer 1

Proteins, lipids, carbs

Question 2

Are biological membranes (a)symmetric?

Answer 2

Asymmetric

Question 3

Under physiological conditions, are membranes fluid or rigid?

Answer 3

Fluid

Question 4

Which forms do amphipathic lipids assume in an aqueous environment?

Answer 4

Micelles

Lipid bilayers

Question 5

Phospholipids, the lipid components of biological membranes, are comprised of which 4 components?

Answer 5

Fatty acid(s)
Backbone (sometimes glycerol)
Phosphate
Alcohol head group

Question 6

What is the phospholipid backbone in phosphoglycerides?

Answer 6

Glycerol

Question 7

What is the phospholipid backbone in sphingomyelin?

Answer 7

Sphingosine

Question 8

What two elements comprise phospholipid head groups?

Answer 8

Phosphate and alcohol

Question 9

Which four alcohols commonly form phospholipid head groups?

Answer 9

Serine
Ethanolamine
Choline
Inositol

Question 10

List two other membrane lipids

Answer 10

Glycolipids

Cholesterol

Question 11

What is the hydrophobic part of phosphoglycerides?

Answer 11

Fatty acid chains

Question 12

What is the hydrophilic part of phosphoglycerides?

Answer 12

Phosphorylated alcohol

Question 13

What is the hydrophobic part of sphingomyelin?

Answer 13

Fatty acid chains

Hydrocarbon chain of sphingosine

Question 14

What is the hydrophilic part of sphingomyelin?

Answer 14

Phosphoryl choline

Question 15

What is the hydrophobic part of glycolipid?

Answer 15

Fatty acid chain

Hydrocarbon chain of sphingosine

Question 16

What is the hydrophilic part of glycolipid?

Answer 16

1+ sugars

Question 17

What is the hydrophobic part of cholesterol?

Answer 17

Everything except -OH

Question 18

What is the hydrophilic part of cholesterol?

Answer 18

-OH group

Question 19

Which four forces drive spontaneous formation of lipid bilayers in aqueous solution?

Answer 19

Hydrophobic effect - primary
Van der waals forces - close packing of tails
Electrostatic + H-bond - between polar head groups and water molecules

Question 20

Is transverse diffusion of membrane lipids fast or slow?

Answer 20

Slow

Protein mediated

Question 21

Is lateral diffusion of membrane lipids fast or slow?

Answer 21

Fast

Question 22

Do longer hydrocarbon chains make a membrane more fluid or more rigid?

Answer 22

More rigid

More van der waals interactions

Question 23

Does unsaturation of hydrocarbon chains make a membrane more fluid or more rigid?

Answer 23

More fluid

Can’t pack as tightly

Question 24

Does cholesterol increase or decrease membrane fluidity?

Answer 24

Decreases fluidity Makes membrane more rigid Blocks large motions

Question 25

How does cholesterol help membranes stay fluid over the range of physiological temperatures, even though it decreases membrane fluidity?

Answer 25

Doesn't allow as much movement... But also keeps lipids from packing too tightly so membranes can't solidify into gel phase

Question 26

Which two factors determine how well a molecule will be able to pass through a membrane without assistance?

Answer 26

Polarity and size

Question 27

How does liposome delivery of a drug work?

Answer 27

Drug is packaged into liposomes, targeted with membrane tag

Question 28

How are peripheral membrane proteins attached?

Answer 28

Bound to surface of membrane or to other integral membrane proteins

Question 29

How are integral membrane proteins attached?

Answer 29

Penetrate lipid bilayer

Question 30

In what structure do integral membrane proteins usually cross the membrane?

Answer 30

Alpha helices

Question 31

What feature predicts whether a protein will be an integral membrane protein and how many times it will pass the membrane?

Answer 31

Polarity of distinct regions

Question 32

In the fluid mosaic model of membranes, what type of diffusion of membrane proteins is possible?

Answer 32

Lateral only. No transverse

Question 33

In the fluid mosaic model, what is the solvent for membrane proteins?

Answer 33

Lipid bilayer is solvent

Question 34

Why don't lipid rafts fit into the fluid mosaic model well?

Answer 34

Less fluid, more resistant to detergent solubilization

Question 35

In what four processes do lipid rafts participate?

Answer 35

Signal transduction Protein sorting Recognition Viral entry or exit from cell