Biology 2.2.7: Phospholipids + Cholesterol

Question 1

what is the structure of a phospholipid?

Answer 1

have the same structure as triglycerides but replace one of the fatty acids with a phosphate group.

Question 2

what reaction occurs to form a phospholipid?

Answer 2

a condensation reaction between OH group on the phosphoric acid molecule and one of the OH groups of the glycerol

Question 3

what is the phospholipids behaviour in water?

Answer 3

the phosphate head is hydrophilic so attracted to water due to its polarity and the fatty acid tail is hydrophobic so repels water due to being non-polar.

Question 4

how do phospholipids work in living organisms?

Answer 4

a phospholipid bilayer is formed to created a cell membrane which allows only small and non-polar molecules to pass through due to its selective permeability.

Question 5

what is cholesterol?

Answer 5

a steroid alcohol - a type of lipid which is not made glycerol or fatty acids.

Question 6

what is the structure of cholesterol?

Answer 6

its made of four carbon-based rings and is hydrophobic, so can sit in the hydrophobic part of the bilayer.

Question 7

what is the function of cholesterol?

Answer 7

it regulates the fluidity of the membrane, preventing it from becoming to fluid or too stiff

Question 8

what are the steroid hormones made from cholesterol?

Answer 8

testosterone, oestrogen and vitamin D