1.5 lipids

Question 1

what 4 characteristics do all lipids share?

Answer 1

• all contain C,H,O
• proportion of O:CH is smaller than in carbohydrates
• insoluble in water
• soluble in organic solvents e.g. alcohol and acetone

Question 2

how do lipids contribute to the cell- surface membrane?

Answer 2

• phospholipids contribute to the flexibility

- transfer lipid- soluble substances across them

Question 3

4 roles of lipids

Answer 3

• source of energy
• waterproofing
• insulation
• protection

Question 4

what are the 2 main groups of lipids

Answer 4

phospholipids and triglycerides

Question 5

why are lipids good at waterproofing?

Answer 5

not soluble in water

Question 6

why are lipids a good source of energy?

Answer 6

when oxidised they release x2 amount of energy compared to the same mass of carbohydrate

Question 7

why are lipids a good insulator?

Answer 7

slow conductors of heat

slow conductors of electricity

Question 8

what is a saturated fatty acid?

Answer 8

all carbon- carbon single bonds

Question 9

what is a mono-unsaturated fatty acid?

Answer 9

one carbon- carbon double bond

Question 10

what is a polyunsaturated fatty acid?

Answer 10

more than one carbon- carbon double bond

Question 11

draw a basic diagram of a triglyceride

Answer 11

see page 16

Question 12

draw one molecule of glycerol

Answer 12

see page 16

Question 13

what are triglycerides made up of?

Answer 13

3 fatty acid and 1 glycerol

Question 14

what bond is formed when a fatty acid reacts with a glycerol molecule?

Answer 14

ester bond

Question 15

why are fats made up of saturated fatty acids?

Answer 15

• no double bonds

- pack closely together

Question 16

what state is fats at, at room temperature?

Answer 16

solids

Question 17

what state is oils at, at room temperature?

Answer 17

liquid

Question 18

why are triglycerides insoluble in water?

Answer 18

large and non- polar

Question 19

why are triglycerides good storage molecules?

Answer 19

• low mass: energy ratio -> large energy can be stored in a small volume
• large -> doesn’t diffuse out of the cell
• insoluble-> doesn’t affect water potential
• high ratio of CH: C-> good source of energy

Question 20

why is it important that triglycerides have a high hydrogen: oxygen ratio?

Answer 20

release water when oxidised so provides a source of energy

Question 21

which part of a phospholipid is hydrophobic?

Answer 21

tail

Question 22

which part of a phospholipid is hydrophilic?

Answer 22

head

Question 23

why is it important that triglycerides have a high CH: C ratio?

Answer 23

excellent source of energy

Question 24

draw the basic drawing diagram of phospholipids

Answer 24

see page 17

Question 25

test for lipids

Answer 25

1. add ethanol
2. shake thoroughly
3. add water
4. shake gently
5. cloudy- white precipitate

Question 26

what are phospholipids made up of?

Answer 26

2 fatty acids, a glycerol and a phosphate

Question 27

draw a more detailed diagram of phospholipid

Answer 27

see page 17

Question 28

what 2 molecules form glycolipids?

Answer 28

phospholipids and carbohydrates

Question 29

what are glycolipids involved in?

Answer 29

cell recognition