Cell Membrane Structure

Question 1

The cell-surface membrane is what?

Answer 1

Partially permeable - it let’s some molecules through but not others

Question 2

How do substances move across the cell-surface membrane?

Answer 2

Diffusion, osmosis and active transport

Question 3

Cell-surface membranes have a what structure?

Answer 3

Fluid mosaic

Question 4

Explain the fluid mosaic model

Answer 4

Phospholipids form a continuous bilayer - the bilayer is fluid because the phospholipids are always moving. Cholesterol is present in the bilayer. Proteins are scattered within the bilayer like a mosaic. Some proteins can move sideways, some are fixed in position

Question 5

What proteins are found in-between the phospholipid bilayer in the cell-surface membrane?

Answer 5

Channel proteins and carrier proteins which allow large molecules to pass through the membrane. Receptor proteins allow the cell to detect chemicals, this signals the cell to respond in some way

Question 6

Whats is a glycoprotein?

Answer 6

A protein with a polysaccharide chain attached

Question 7

What is a glycolipid?

Answer 7

A lipid with a polysaccharide chain attached

Question 8

Phospholipid form a barrier to dissolved substances, explain

Answer 8

They have a hydrophobic tail and a hydrophilic head. The molecules automatically arrange themselves into a bilayer - the heads face out towards the water on either side of the membrane. The centre of the bilayer is hydrophobic so water-soluble substances can’t pass through it

Question 9

Cholesterol gives the membrane stability, explain

Answer 9

Cholesterol is a lipid and fits between the phospholipids and binds to their hydrophobic tails, causing them to pack more closely together, restricting their movement and making the membrane more rigid. It helps maintain the shape of animal cells.