Lipids

Question 1

Roles of lipids

Answer 1

Energy source - when oxidised they release 2 x the energy of carbs

Waterproofing - insoluble in water (waxy cuticle)

Insulation - slow conductor of heat and electrical insulation

Protection - layer of fat around organs

Question 2

Features of lipids

Answer 2

Made of C, H, and O
Low proportion of oxygen compared to carbs
Insoluble in water
Main groups = triglycerides and phospholipids

Question 3

What is tryglyceride made of?

Answer 3

One glycerol
3 fatty acids

Question 4

What is the R group?

Answer 4

Long chain hydrocarbon

Saturated = no double bonds between carbon atoms
(Tend to be solid at room temp)

Unsaturated (mono or poly) = double bonds between carbon atoms
( tend to be liquid at room temp)

Question 5

Structure of triglycerides

Answer 5

High ratio of C-H bonds (good store of energy)
High ratio of H-O bonds (water released when oxidised)
Low mass to energy ratio
Large and non-polar (insoluble)

Question 6

What makes phospholipids polar?

Answer 6

One fatty acid is replaced by a phosphate group which is negatively charged

Question 7

What things cannot diffuse across the bilayer?

Answer 7

Large molecules.
Ions
water molecules
Glucose

Question 8

Test for lipids

Answer 8

Grind /crush sample with ethanol
Add equal volume of water and shake
A white emulsion will form if lipids are present