Lecture 9: Biological Membrane Structure

Question 1

Plasma membrane functions

Answer 1

1. Isolate cytoplasm from external environment and containment of cellular contents
2. transport of molecules into/out of the cell
3. cell recognition/communication

Question 2

How do phospholipids species differ to give different properties to the bilayer?

Answer 2

1. ratio of saturated to unsaturated acid tails affects fluidity (viscosity) of membrane
2. species of phospholipids from inner to outer part of the bilayer

Question 3

Membrane is directional

Answer 3

(protein movement) ER -> Golgi apparatus -> vesicle -> secreted

Question 4

Peripheral proteins

Answer 4

not embedded in the bilayer

Question 5

integral proteins

Answer 5

partially or wholly embedded in the bilayer

Question 6

transmembrane proteins

Answer 6

extends all the way through the membranes

Question 7

Functions of membrane proteins

Answer 7

1. transport
2. enzymatic activity
3. signal transduction
4. cell-cell recognition

Question 8

Cholesterol

Answer 8

1. stabilizes the membrane
2. breaks up hydrophobic interactions between fatty acids
3. ratio of C/stat vs unstat PL affects membrane fluidity

Question 9

carbohydrates

Answer 9

short oligosaccharides covalently bond to proteins (glycoproteins) and lipids (glycolipids) interact with molecules on outside of cell

Question 10

Components of cell membrane

Answer 10

1. phospholipids
2. cholesterol
3. carbohydrates
4. proteins

Question 11

Temperature vs cells w mixed proteins

Answer 11

as temperature rises, mixed proteins increases and so does fluidity

Question 12

How to increase membrane fluidity?

Answer 12

1. shorter fatty acids with more C=C
2. increase cholesterol to phospholipid ratio
3. increase number of proteins

Question 13

what happens when temperature is decreased?

Answer 13

fluidity is decreased