Chapter 11: Membrane Structure

Question 1

Most common phospholipid in cell membranes?

Parts?

Answer 1

phosphatidylcholine

choline (hydrophilic head)

Phosphate (links choline to glycerol)

Glycerol (links phosphate to 2 hydrocarbons)

Both hydrocarbons (originated as fatty acids)

Question 2

all membrane lipids are what in terms of hydrophobic/phillic

Answer 2

amphipathic

Question 3

Liposomes?

Formed by

Answer 3

phospholipid vesicles

pure phospholipids

Question 4

fluidity of a membrane is influenced by what two things?

Answer 4

temp

tail types (unsaturated tails increase fluidity)

Question 5

Cholesterol ___ membranes and ____ permeability by

Answer 5

stiffens, decreases

fitting in gaps

Question 6

Scramblases?

Flippases?

Answer 6

after synthesis and addition of phospholipids to cytosolic monolayer, scramblases randomly transfer PPLs to other side leading to symmetric growth

Same family as scramblases
After delivery of new membrane (Addition to both layers), they transfer specific lipids to cytosolic monolayer to maintain asymmetry of the bilayer (essential for vesicular fusion)

Question 7

Phospholipids and glycolipids are distributed ____ in bilayer

Answer 7

unevenly

Question 8

two sides of bilayer?

what happens to them in budding and fusion?

Answer 8

cytosolic and Non cytosolic

they are maintained!

*non cytosolic side is inside of organelle, but outside of cell membrane

Question 9

Transmembrane hydrophilic pores formed by

Answer 9

multiple alpha helices

Question 10

Detergents do what?

they are similar to ___ with a minor difference of ___

they aggregate into ____

can be used to artificially ___

two most common ones?

Answer 10

break up bilayer by solubizing membrane proteins by squeezing between them and the bilayer lipids and separating them

lipids, only 1 tail

micelles

incorporate proteins into bilayer

SDS and Triton X-100

Question 11

Cell cortex:

determines?

____ dimers form cortex of human RBCs

Answer 11

meshwork of fibrous proteins attached to cytosolic face of membrane

shape of cell and membrane properties

spectrin

Question 12

4 methods of plasma membrane protein lateral mobility restriction

Answer 12

they can be tethered to

1. Cell cortext
2. ECM molecules
3. Proteins on surface of other cell
4. Diffusion barriers (restrict protein to moving within a domain, allow for some lateral movement)

Question 13

Eukaryotic cell surfaces are coated with ____

attached to:

function?

Answer 13

sugars

lipids and proteins on cell surface

cell-cell recognition and adhesion

Question 14

___ techniques can measure lateral diffusion rates of membrane lipids and proteins

Protein motion patterns are tracked by ____

when a protein is bound to cytoskeleton, result is?

Answer 14

photobleaching

single-particle tracking microscopy

immobilization

Question 15

The carbohydrate-rich zone on the outside of animal cell membranes that provides protection and cell recognition is called the __________

Answer 15

glycocalyx

Question 16

in the Na⁺/K⁺ pump, how many Na⁺ ions are exported for every K⁺ ion imported?

Answer 16

3 Na⁺ out and 2 K⁺ in per ATP hydrolyzed

Question 17

How does cholesterol affect membrane fluidity at (i) low and (ii) high temperatures

Answer 17

At high temperatures, cholesterol reduces membrane fluidity by preventing the phospholipids from spreading too far apart, while at low temperatures, it increases fluidity by preventing the phospholipids from packing too tightly together

Question 18

why do glycolipids face non-cytosolic side of membranes?

Answer 18

they face outside because glycosylation occurs in lumen/Golgi and vesicular trafficking preserves orientation