Membrane dynamics

Question 1

Can membranes undergo phase transitions?

Answer 1

Yes

Question 2

Permeable to what?

Answer 2

To small polar solutes and nonpolar compounds

Question 3

Permeability can be artificially increased by what?

Answer 3

Chemical treatment

Question 4

Membrane lipids are in constant motion and degree of fluidity depends on

Answer 4

Lipid composition and temperature

Question 5

Membranes must be in gel or fluid state for proper function?

Answer 5

Fluid

Question 6

Fatty acid composition and cholesterol content controls what

Answer 6

Membrane fluidity

Question 7

What is Tm

Answer 7

The temperature at which a membrane transitions from being highly ordered to very fluid is called the melting temperature/transition temp

Question 8

The transition temperature is dependent on what 2 things

Answer 8

Length of fatty acids in the membrane lipid and the degree of cis unsaturation

Question 9

Cholesterol helps to maintain what in membranes in animals?

Answer 9

Maintain proper membrane fluidity

Question 10

More fluid membranes require what and why?

Answer 10

Require shorter and more unsaturated fatty acids. Unsaturated fatty acids have a lower melting point than saturated.

Question 11

At a higher temperature cell membranes need more of what fatty acids to maintain what?

Answer 11

Need more saturated fatty acids to maintain integrity

Question 12

At lower temperatures cells need more of what fatty acids to maintain what?

Answer 12

More unsaturated fatty acids to maintain fluidity

Question 13

Sterols and hopanols increase what?

Answer 13

Membrane rigidity and permeability

Question 14

What cell membranes contain hopanols?

Answer 14

Those of prokaryotes

Question 15

Name the sterols in animals, plants and fungi?

Answer 15

Cholesterol in animals
Phytosterols in plants
Ergosterol in fungi

Question 16

Lipid distribution in a single leaflet is not what?

Answer 16

Random or uniform

Question 17

Lipid rafts contain what type of lipid

Answer 17

Clusters of glycosphingolipids with longer than usual tails

Question 18

Lipid rafts are more or less ordered?

Answer 18

More ordered

Question 19

Lipid rafts contain specific acylated proteins that are what?

Answer 19

Doubly or triply acylated

Question 20

Lipid rafts allow segregation of what

Answer 20

Segregation of proteins in the membrane

Question 21

Overall 4 points about lipid rafts

Answer 21

Contain clusters of glycosphingolipids
More ordered
Doubly/Triply acylated proteins
Allow segregation of proteins in membrane

Question 22

What 2 things demonstrate lateral mobility in biomembranes?

Answer 22

Lipids and integral proteins

Question 23

Mobility (diffusion) of given membrane component depends on what 4 things

Answer 23

Size of the molecule, interactions with other molecules, temp and lipid composition

Question 24

Mobility can be measured by what

Answer 24

FRAP

Question 25

How does FRAP work?

Answer 25

Monitor lateral lipid diffusion by monitoring the rate of fluorescence return.
From the rate of return of lipids, the diffusion coefficient of a lipid in the leaflet can be determined

Question 26

What does FRAP stand for

Answer 26

Fluorescence recovery after photobleaching

Question 27

3 main steps in FRAP

Answer 27

1) Label outside of the cell with fluorescent probes on lipids
2) Photobleach, intense laser beam bleaches small area
3) Measure recovery, measure rate of fluorescence return