Biological membranes

Question 1

Cholestrol

Answer 1

• present to make the membrane more rigid and reduce the lateral movement of the
  phospholipids.

-prevents the leakage of water and dissolved ions from the cell as it is very hydrophobic.

Question 2

Intrinsic proteins

Answer 2

These may be integrated throughout the membrane. Intrinsic proteins

• include carrier proteins which allow
  substances to cross the membrane.

Question 3

Extrinsic proteins

Answer 3

On the surface of the membrane

Question 4

Proteins

Answer 4

present to aid movement across the membrane, provide mechanical support and act in conjunction with glycolipds as receptors.

Question 5

Glycolipds

Answer 5

• These are made up of a carbohydrate that is bound to lipids.
• These extend from the surface of the cell
• acts as a cell surface receptors for certain molecules.
• They also allow cells to adhere to one another to form tissues.

Question 6

Glycoproteins

Answer 6

• These are carbohydrates that attach to extrinsic proteins and acts a cell surface receptors and
  neurotransmitters.
• These allow cells to recognise one another as well as attach to form tissues.

Question 7

What is the main function of plasma membranes

Answer 7

Defines the borders of cells and most organelles.
-is selectively permeable. means that the membrane allows some materials to freely enter or leave the cell/organelle, while other materials cannot move freely.

Question 8

The rate of gas exchange by diffusion becomes more rapid as:

Answer 8

• The surface area of the surface increases
• The diffusion distance decreases
• The diffusion gradient becomes more steep
• The temperature increases

Question 9

Structure of a phospholipid

Answer 9

• consist of glycerol, two fatty acids, and a phosphate-linked head group.
• The hydrophilic phospholipid head faces outwards and the hydrophobic fatty acids faces inwards

Question 10

Structure of cholestrol

Answer 10

a lipid that sits with phospholipids in the core of the membrane.

Question 11

Thickness of phospholipid

Answer 11

The molecules arrange themselves into a bilayer which ranges from 5 to 10 nm in thickness.

Question 12

What factors affect permeabiity of cells?

Answer 12

Temperature
pH
Solvent concentration

Question 13

Permeability

Answer 13

How easy it is for substances to pass through

Question 14

One type of mutation in the CFTR protein prevents the transport of chloride ions through the channel.

Which of the following is most likely to be observed in the lungs of patients with this mutation?

Answer 14

Sticky mucus with high electryote concentration

Question 15

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane?

Answer 15

Phospholipids are amphipathic molecules. The polar head faced towards the water and the non polar fatty acid tails face towards other fatty acid tails

Question 16

Why is it advantageous for the plasma membrane to be fluid in nature?

Answer 16

Fluidity allows greater flexibility to the cell and motion of membrane components required for transport

Question 17

Explain why glucose cannot pass directly through the cell membrane.

Answer 17

The plasma membrane is selectively permeable to polar molecules, a transport protein is required for larger molecules.

Question 18

List 3 biological molecules which might be found in the plasma membrane.

Answer 18

Phospholipids
Cholestrol
Protein Or Carbohydrates

Question 19

In which cell type is cholesterol found in the plasma membrane?

Answer 19

Eukaryotes

Question 20

What organism is often used in experiments to measure membrane permeability through the release of its pigment?

Answer 20

Beetroot

Question 21

What effect would increasing temperature have on the permeability of the plasma membrane?

Answer 21

Increase