triglycerides

Question 1

are triglycerides structural or storage molecules?

Answer 1

storage

Question 2

what properties of triglycerides make them ideal storage compounds?

Answer 2

they yield twice as much energy as carbohydrates when oxidised (respired) and being insoluble, are osmotically inactive

Question 3

what do triglycerides consist of?

Answer 3

fats (solids) and oils (liquids) at room temperature

Question 4

are triglycerides always insoluble?

Answer 4

although insoluble in water, they are soluble in a range of organic solvents eg alcohol

Question 5

how are triglycerides formed?

Answer 5

triglycerides are one type of lipid formed by joining 3 fatty acids and 1 glycerol molecule during a condensation reaction with the loss of 3 water molecules

Question 6

draw the structure of glycerol?

Answer 6

see notes

Question 7

draw the structure of a fatty acid?

Answer 7

see notes

Question 8

what’s the general formula of a fatty acid?

Answer 8

R-COOH

Question 9

what does the R and the COOH in the fatty acid represent?

Answer 9

the R represents a long hydrocarbon chain and COOH is a carboxylic acid group

Question 10

what two types of chain can the fatty acid have?

Answer 10

• saturated where there is no double bonds between the carbon atoms, there is the maximum number of hydrogens, it’s a solid at room temperature, it’s a straight chain, it’s packed tightly together so a large amount of energy is needed to separate them
• unsaturated where there is one or more double bonds between the carbon atoms, there isn’t the maximum number of hydrogens, it’s a liquid at room temperature, it’s a kinked chain, it’s less tightly packed so less energy is needed to separate them

Question 11

how is the bond formed between the glycerol and 3 fatty acids and what is this bond called?

Answer 11

three Hs are lost from the OHs in the glycerol and each fatty acid loses an OH, forming an ester bond between the three O’s from the glycerol and the three C’s from the fatty acids

Question 12

what are simple and mixed triglycerides?

Answer 12

simple triglycerides - all three fatty acids are the same
mixed triglyceride - the fatty acids are different

Question 13

how are lipids hydrolysed?

Answer 13

lipids are hydrolysed into fatty acids and glycerol by
- heating with acid or alkali
- using the enzyme lipase at an optimum temperature and pH