Membranes

Question 1

The cells membrane is described as fluid mosaic, what does this mean?

Answer 1

Fluid- phospholipids are constantly moving

Mosaic- proteins are scattered through the bilayer

Question 2

How does phospholipids arrange themselves in the bilayer?

Answer 2

The hydrophilic head facing outwards & hydrophilic tail facing inwards

Question 3

Why do phospholipids arrange themselves in a particular way?

Answer 3

Because the centre of the bilayer doesn’t like water soluble substances and the hydrophobic tails don’t allow these molecules to pass through.

Question 4

What proteins are in the membrane?

Answer 4

-Extrinsic proteins- on the surface

(Helps in the transport of molecules & acts as receptor molecules) e.g: receptor proteins

-cell recognition molecules- glycoproteins- has receptors and can recognise molecules which cause some change to the cells physiology

(glycolipids)

Intrinsic proteins- span the membrane between the outside and inside of the cell

Question 5

How isglucose transported from the lumen into the blood?

Answer 5

1. Glucose is actively transported from the ephitheal cell to the blood to creat a low concentration in the Spithead cell.
2. Then glucose attaches to a sodium ion and then diffuses from the lumen into the Spithead cell via a glucose- sodium co transporter
3. Then because of the low concentration of glucose in the blood it is then diffused into the blood using facilitated diffusion which uses a protein channel