Lipids

Question 1

What is a lipid + their properties?

Answer 1

• generalised term for fats and oils
• contain carbon, hydrogen and oxygen
• proportion of O to C + H is smaller than carbohydrates’
• insoluble in water but soluble in organic solvents

Question 2

What are some roles of lipids?

Answer 2

• phospholipids make up plasma membrane
• provide energy -> when oxidised provide 2x energy as carbs
• insulators, slow heat conductors so retain body heat
• some hormones are lipid based e.g testosterone
• offer protection of delicate organs

Question 3

What is the structure of triglycerides?

Answer 3

3 fatty acids combined with a glycerol

Question 4

What is a fatty acid?

Answer 4

Long chain hydrocarbons containing a COOH group

Question 5

What are the differences between a saturated and unsaturated fatty acid?

Answer 5

-Saturated = hydrocarbon has only single bonds
- form saturated lipids which are solid at room temp
_Unsaturated = hydrocarbon chain has at least 1 double bond
- forms unsaturated lipids = liquid at room temp

Question 6

How are triglycerides formed?

Answer 6

3 condensation réaction between the glycerol and the 3 fatty acids, forming 3 ester bonds

Question 7

What is cholesterol’s properties?

Answer 7

• insoluble in water
• must combine with proteins to be transported in the bloodstream, forming lipoproteins

Question 8

Describe the formation and function of low-density lipoproteins

Answer 8

• triglycerides from fats in diet combine w/ cholesterol and proteins to form LDLs, which transport cholesterol to body cells
• circulate in bloodstream and bind to receptor cells on membranes before being taken in
• excess LDLs overload membranes, means high cholesterol levels in blood which may be deposited into artery wall causing an atheroma

Question 9

Describe the formation and function of high density lipoproteins

Answer 9

• higher % of protein + less cholesterol; are made when triglycerides from fats combine with cholesterol and proteins
• HDLs transport cholesterol from body tissues to the liver where it is broken down
• lowers blood cholesterol levels + helps removing fatty plaques

Question 10

What diet increases/decreases LDLs and HDLs?

Answer 10

• saturated fat diet = increases both LDLs and HDLs but more LDLs
• unsaturated fat in diet = decreases both LDL and HDL levels

Question 11

Draw/Describe the formation reaction for a triglyceride

Answer 11

3x Fatty acid tails with HO-C=O (carboxyl groups) attached, glycerol = 3 carbons each bonded to H, H and OH and other C