Cell surface membrane

Question 1

Describe cholesterol and its role (in cell membranes)

Answer 1

• embedded in the bilayer
• acts as a buffer for membrane fluidity. (at high temperatures prevents fluidity from rising too high, and at low temperatures, prevents membrane becoming solid)
• prevent leakage of water
• reduce lateral movement of other molecules

Question 2

What are 2 types of proteins found in cell membranes?

Answer 2

• integral; span the whole of the membrane (e.g transport proteins)
• extrinsic; only one side of the bilayer
  (give support or act with glycolipids as cell receptors)

Question 3

What are 6 functions of proteins in cell-surface membranes?

Answer 3

• structural support
• protein channels; transport water soluble substances
• allow active transport; through carrier proteins
• form cell-surface receptors for identifying cells
• help cells adhere together
• act as receptors

Question 4

What are 3 functions of glycolipids in cell membranes?

Answer 4

• recognition sites
• maintain stability
• help cells attach to each other

Question 5

What are the functions of phospholipids in cell-surface membranes?

Answer 5

• Lipid soluble substances to pass through
• Flexibility and self-sealing
• Stop water soluble substance entering and leaving cells

Question 6

Describe the bilayer

Answer 6

formed from two layers of phospholipids. These molecules have hydrophilic heads which face out of the bilayer and hydrophobic tails which face into the bilayer, so they don’t come in to contact with water .

Question 7

Why is the structure of cell membranes called the fluid mosaic model?

Answer 7

fluid- as the phospholipids allow movement
mosaic- as it is made up of many different components

Question 8

How does temperature impact cell surface membranes?

Answer 8

an increase in temperature increases the fluidity of the membrane, as a result increasing it’s permeability

Question 9

How does pH impact cell surface membranes?

Answer 9

it impacts the protein structure of the proteins in the cell membrane

Question 10

How does solute concentration impact cell surface membranes?

Answer 10

Phsopholipid bilayer is dissolved more easily, increasing its permeability

Question 11

How does colour indicate the permeability of membranes when investigating using beetroot?

Answer 11

The darker the solution of beetroot, the more pigment has been released because the membrane is more permeable. A darker solution will have a higher reading for absorbance

Question 12

Why is fluidity an important characteristic of cell membranes?

Answer 12

It allows flexibility for the cell, increased motion needed in transport

Question 13

What is a glycolipid?

Answer 13

phospholipid with a carbohydrate chain attached

Question 14

What is a glycoprotein?

Answer 14

a protein with a carbohydrate group attached