Structure Of Plasma Membranes

Question 1

What are the functions of plasma and cell surface membranes?

Answer 1

Controls passage of molecules in and out of cells/organelles
Cell surface membrane forms boundaries between the cell cytoplasm and cells environment

Question 2

What are the 5 main components of a plasma membrane?

Answer 2

Phospholipids
Proteins
Cholesterol
Glycoproteins
Glycolipids

Question 3

Function of phospholipid bilayer

Answer 3

Allows lipid-soluble substances to enter and leave the cell or organelle
Prevents water-soluble substances entering and leaving the cell
Makes the membrane flexible and self- sealing

Question 4

Proteins functions in plasma membranes

Answer 4

Structural support
Helps cells attach to each other
Channel proteins for water soluble substances in facilitated diffusion
Carrier proteins for active transport
Cell surface receptors

Question 5

Cholesterol functions in plasma membrane

Answer 5

Adds strength to the membrane
Reduces movement of other molecules
Makes the membrane less fluid at high temperatures
Prevents leakage of water and dissolved ions

Question 6

Glycolipid

Answer 6

Lipid covalently bonded to a carbohydrate

Question 7

Glycolipids functions in a plasma membrane

Answer 7

Act as recognition sites: cell surface receptors for specific chemicals
Help maintain stability of the membrane
Help cells attach to each other forming tissues

Question 8

Glycoprotein

Answer 8

An extrinsic protein covalently banded to a carbohydrate

Question 9

Glycoproteins functions in a plasma membrane

Answer 9

Recognition sites- cell surface receptors for specific chemicals
Help cells attach to each other forming tissues
Allow cells to recognise each other

Question 10

Plasma membrane is known as the fluid- mosaic model
Why fluid?

Answer 10

Protein and phospholipid molecules can move relative to each other
The membrane is flexible and constantly changing shape

Question 11

Plasma membrane is known as the fluid- mosaic model
Why a mosaic?

Answer 11

Like the tiles in a mosaic the proteins embedded in the phospholipid