Chap4 Plasma Membranes

Question 1

What is the main component of plasma membranes?

Answer 1

Phospholipids
(phosphate attached to two fatty acids)

Question 2

What are the main functions of membrane?

Answer 2

Controls what goes in/out of cell
allow cell to change shape
site of biochemical reactions
isolates organelles from cytoplasm

Question 3

Describe structure of phospholipid

Answer 3

Hydrophilic head faces water (outwards) hydrophobic tail faces away from water (inwards) all due to polar nature of cell

Question 4

What two structures formed when phospholipid exposed to water?

Answer 4

Bilayer and micelle

Question 5

What is the role of intrinsic proteins?

Answer 5

Carrier proteins or channels that help transport substances vital for cells function but cannot diffuse across membrane

Question 6

What is the role of extrinsic proteins?
Give Example

Answer 6

(extracellular) act as receptors for hormones or neurotransmitters
Eg) glycoprotein
(carbohydrate and protein)

Question 7

What is chemical equation of cholesterol?

Answer 7

C27 H46 O

Question 8

What is the role of cholesterol?

Answer 8

Controls membrane fluidity.
Keeps membrane stable at normal body temperature because without it cell would burst open

Question 9

Describe movement of proteins

Answer 9

Most move sideways along bilayer
large proteins are in fixed position

Question 10

What two factors effect membrane permeability?

Answer 10

Temperature and solvent

Question 11

How does temperature effect permeability of membrane?

Answer 11

High temperature phospholipid gains more kinetic energy, raising permeability, leading to membrane breakdown.

Denatures protein within membrane and can impact carrier proteins directly or alter fluid mosaic.

Question 12

How does solvent effect permeability of membrane?
Give Example

Answer 12

Dissolves phospholipid membrane
Eg) alcohol alters permeability of neurone membrane in brain