membrane components

Question 1

what do phospholipids form a barrier to ?

Answer 1

water soluble substances

Question 2

describe the structure of a phospholipids ?

Answer 2

The head is hydrophilic
The tail is hydrophobic

Question 3

how do phospholipids become a bilayer ?

Answer 3

The molecules automatically arrange themselves into a bilayer — the heads face out towards the water on either side of the membrane

Question 4

how does the bilayer help with diffusion ?

Answer 4

The centre of the bilayer is hydrophobic so the membrane doesn’t allow water-soluble substances (like ions and polar molecules) to diffuse through it.
Small, non-polar substances (e.g. carbon dioxide) and water can diffuse through the membrane

Question 5

where is cholesterol present ?

Answer 5

all cell membranes except bacterial cell membranes

Question 6

what does cholesterol do for the cell membrane ?

Answer 6

gives it stability

Question 7

where is the choloersterol in the bilayer ?

Answer 7

between the phospholipids

Question 8

what does cholesterol do for the phospholipids ?

Answer 8

binds to the hydrophobic tails of the phospholipids, causing them to pack more closely together.
This restricts the movement of the phospholipids, making the membrane less fluid and more rigid.

Question 9

what does cholesterol do for animal cells ?

Answer 9

helps maintain the shape as they don’t have cell walls

Question 10

cholesterol is important for what cells ?

Answer 10

cells that aren’t supported by other cells, e.g. red blood cells, which float free in the blood

Question 11

What does cholesterol do for polar molecules ?

Answer 11

Cholesterol also has hydrophobic regions, so it’s able to create a further barrier to polar substances moving through the membrane.