L9 Membranes

Question 1

What is the function of the membrane?

Answer 1

Selectively permeable barrier.

Question 2

What are the qualities of the membrane?

Answer 2

1. Self healing
2. Cell communication
3. Molecule/ion import/export
4. Cell growth/Flexible
5. Fluid

Question 3

What are membranes made of?

Answer 3

Lipids and embedded proteins.

Question 4

Building block of lipids

Answer 4

Fatty acids

Question 5

What quality of fatty acids leads to bilayer formation?

Answer 5

Amphipathic

Question 6

What is fluidity?

Answer 6

The ease of movement of lipids within the plane of the bilayer.

Question 7

Why is fluidity important?

Answer 7

1. Proteins need to interact
2. Molecules need to move from sites of insertion.
3. Membranes need to fuse
4. Membranes need to grow and pinch off.

Question 8

What does it mean if a membrane is assymmetric?

Answer 8

The lipid composition of one side is different.

Question 9

What can impact membrane fluidity?

Answer 9

1. Temperature
2. Cholesterol
3. Plasma-membrane deformation

Question 10

What does cholesterol do?

Answer 10

Its short and stiff structure fills the gaps between hydrophobic heads of phospholipids. Stiffens the bilayer!

Question 11

What two qualities of fatty acids determine membrane fluidity?

Answer 11

Length (shorter = more fluid)
Saturation (more kinks=more space)

Question 12

Cell cortex function:

Answer 12

Reinforces plasma membrane structure/shape.

Question 13

What is the Glycocalyx?

Answer 13

The carbohydrate outer coating of the bilayer.

Question 14

Function of glycocalyx?

Answer 14

1. Protect
2. Lubricate
3. Recognition
4. Adhesion

Question 15

Glycocalyx made of?

Answer 15

Oligosaccharides and polysaccharides

Question 16

Lectins are..?

Answer 16

Transmembrane proteins that bind to the sugar side chains of the glycocalyx - cell membrane adhesion.

Question 17

FRAP stands for…

Answer 17

Fluorescence REcovery After Photobleaching

Question 18

FRAP is used to measure what two things?

Answer 18

1. Lipid mobility
2. Membrane protein mobility

Question 19

How to read FRAP data?

Answer 19

Good recovery demonstrates membrane fluidity through diffusion.

Question 20

How can lateral mobility of proteins be restricted?

Answer 20

1. Tethers to cell cortex, extracellular matrix molecules, or surface proteins of other cells
2. Diffusion barriers restrict p movement to membrane domain

Question 21

Types of membrane proteins?

Answer 21

1. Transmembrane
2. Monolayer-associated
3. Lipid-linked
4. Protein-attached

Question 22

Transmembrane proteins assume what structure to cross the bilayer?

Answer 22

Alpha-Helix, with nonpolar side chains angled outward. Channels cannot be made of a singular alpha helix, they take on shapes made of multiple alpha-helixes or beta-barrels.