Plasma Membrane

Question 1

Membrane Structure

Answer 1

Thin (8nm) flexible sturdy barrier surrounding cytoplasm.

Question 2

What’s in fluid mosaic

Answer 2

Sea of lipids where proteins float. 50% lipid 50% protein held by H bonds. Lipid is barrier (hydrophobic core) to entry and exit of polar substance. Proteins gatekeeper.

Question 3

Phospholipid

Answer 3

Makes up 75% of lipids. Has charged polar head and low energy state tails.

Question 4

What changes properties of membrane fluidity

Answer 4

Tail length- shorter = more fluid
Double bond - more db = more fluid
Less cholesterol = more fluid

Question 5

What does too much cholesterol do

Answer 5

Makes arteries and membranes stiffer

Question 6

How to remove peripheral proteins

Answer 6

protein to protein interactions can use high salt to break the bonds

Question 7

How to remove integral proteins

Answer 7

Break interactions to lipids by using detergent

Question 8

Integral membrane proteins

Answer 8

Amphipathic. Consists of non polar amino acids coiled into helices. Hydrophilic ends interact with aqueous solution.

Question 9

Functions of membrane proteins

Answer 9

Receptors, cell identity markers, linkers, enzymes, ion channels, transport proteins

Question 10

Permeability of membrane

Answer 10

Permeable to
non polar and uncharged molecules (O2 N2 benzene)
lipid soluble (steroids, fatty acid sone vitamins)
small uncharged (water, urea, glycerol CO2)

Question 11

Impermeability of membrane

Answer 11

Large uncharged polar molecules - glucose, amino acids
Impermeable ions (Na+, K+, Cl-)

Question 12

Diffusion

Answer 12

Area of high to low and stops when equilibrium is reached

Question 13

Principles of diffusion

Answer 13

• greater diff in conc between 2 sides of membrane = faster diffusion
  higher temp = faster diffusion
  larger substance size = slower diffusion
  Inc surface area = Inc rate of diffusion
  Inc distance = slows rate of diffusion

Question 14

Physical consequences

Answer 14

Rate of diffusion sets limit on cell size, Inc area for Inc diffusion, thicker membrane = slower rate of diffusion, diffusion is fast over small distance

Question 15

Concentration gradient

Answer 15

Non charged molecules diffuse down concentration gradient

Question 16

Electrical gradient

Answer 16

Movement of ions are influenced by electrochemical gradient. Ions influenced by membrane potential

Question 17

Membranes mimic what

Answer 17

Capacitors as they can seperate and store charge

Question 18

Ion concentrations use how much wresting energy

Answer 18

30% to maintain concentration and electrical gradients and these gradients represent stored energy

Question 19

Osmotic gradient

Answer 19

Water moves to eliminate the osmotic gradient only if membrane is permeable to water

Question 20

Hypo and hyper osmotic

Answer 20

Hypo = low
Hyper = high