Cell membrane structure

Question 1

Describe the role of cell surface membranes

Answer 1

Surrounds a cell and acts as a barrier between the cell and the environment. They are partially permeable

Question 2

What are cell membranes made up of?

Answer 2

Lipids
Proteins
Carbohydrates

Question 3

What do the phospholipids form according the the fluid mosaic model?

Answer 3

A continuous, fluid double layer (bilayer)

Question 4

What do receptor proteins do in the cell surface membranes?

Answer 4

Allows the cell to detect chemicals released from other cells. The chemicals signal the cells to produce a response

Question 5

Describe the movements of proteins in the membrane

Answer 5

Some move sideways and some are fixed

Question 6

What is the name of the polysaccharide chain attached to proteins?

Answer 6

Glycoproteins

Question 7

What is the name of the polysaccharide chain attached to lipids?

Answer 7

Glycolipids

Question 8

Which part of a phospholipid is hydrophilic?

Answer 8

The head

Question 9

Which part of a phospholipid is hydrophobic?

Answer 9

The tail

Question 10

How are the molecules arranged in a bilayer?

Answer 10

Arranged into a bilayer with the heads facing out towards to water on either side of the membrane

Question 11

Describe the centre of the bilayer

Answer 11

It is hydrophobic which means the membrane will not let water soluble substances through

Question 12

What is cholesterol?

Answer 12

A lipid that is present in all cell membranes except of bacteria

Question 13

Describe cholesterol in the membrane

Answer 13

It fits between phospholipids and binds to the hydrophobic tails of the phospholipids causing them to pack more closely together. This restricts movement making the membranes less fluid and more rigid.

Question 14

What does cholesterol do?

Answer 14

Helps to maintain the shape of animal cells

Question 15

What does increasing the temperature of a membrane do?

Answer 15

It increases the permeability of the membrane

Question 16

What happens to the membrane when the temperature is below 0?

Answer 16

Phospholipids have limited energy and are packed close. They have a rigid membrane and the channel and carrier proteins deform increases the permeability.

Question 17

What happens to the membrane when the temperature is between 0 - 45?

Answer 17

Phospholipids can move making the membrane partially permeable. As the temperature increases the phospholipids can move more increasing the permeability.

Question 18

What happens to the membrane when the temperature is above 45?

Answer 18

The bilayer begins to melt and the permeability of the membrane increases. Water inside the cell expands put pressure on the membrane. Channel and carrier proteins deform increasing the permeability.