Biological Membranes

Question 0

Membrane composition

Answer 0

Asymmetric, heterogenous (protein and lipid)

Lipid clusters and lipid-protein aggregates

Question 1

Functions of membranes

Answer 1

Barrier to toxins 
Transport and accumulation of nutrients
Energy transduction
Facilitation of cell motion
Reproduction
Signal transduction
Cell cell interactions

Question 2

Integral membrane proteins

Answer 2

Attached or anchored to the membrane

Globular proteins totally in the membrane

Question 3

Peripheral membrane proteins

Answer 3

Generally globular, interact electrostatically/hydrogen bond with integral membrane proteins

Question 4

Lipid anchor proteins

Answer 4

Proteins attached to membranes through lipid tails

Question 5

Types of lipid anchored proteins

Answer 5

Amide linked myristoyl anchor
Thioester linked fatty acyl anchor
Thioester linked prenyl anchor
Glycosyl phosphatidylinositol anchor

Question 6

Lipid anchor composition

Answer 6

Always myristic acid and N-terminal Gly residue

Question 7

Prenyl

Answer 7

Long chain polyisoprene units

Question 8

Target of isoprene units

Answer 8

C-terminal CAAX motif

Question 9

Farnesyl

Answer 9

3 isoprene units

Question 10

Geranylgeranyl

Answer 10

4 isoprene units

Question 11

Types of lipid movements in membranes

Answer 11

Rotational diffusion, protrusion, flip-flop, lateral diffusion, bond vibrations, Gauche-trans isomerization

Question 12

Membranes at low temperatures

Answer 12

Highly ordered, called solid ordered state, little motion, chains are fully extended, thickness is maximal

Question 13

Membranes at high temperatures

Answer 13

Lots of motion, liquid crystalline phase or liquid disordered state, chains likely to be bent, gets thinner

Question 14

Types of transporters

Answer 14

Passive diffusion, facilitated diffusion, active transport

Question 15

Passive diffusion

Answer 15

Purely entropic, moves down a concentration gradient

Question 16

Facilitated diffusion

Answer 16

Used for charged solutes

Question 17

Active transport

Answer 17

Uses a positive concentration gradient, thermodynamically unfavorable, uses ATP, possible to couple a favorable and unfavorable process