lipids

Question 1

what elements do lipids contain

Answer 1

carbon, hydrogen and oxygen

Question 2

what is the structure of a triglyceride

Answer 2

1 glycerol bonded to 3 fatty acids

Question 3

what is the fatty acid tails structure

Answer 3

carboxyl group bonded to a variable hydrocarbon R group

Question 4

what property do fatty acid tails have

Answer 4

the R hydrocarbon group makes them hydrophobic and so insoluble in water

Question 5

what is the bond called between the glycerol and fatty acid molecule

Answer 5

ester bond

Question 6

how are the ester bonds synthesised

Answer 6

via condensation reactions, each releasing a molecule of water

Question 7

what is a saturated fatty acid

Answer 7

do not contain any C=C bonds

Question 8

what is an unsaturated fatty acid

Answer 8

contains at least one C=C bond

Question 9

what is the structure of a phospholipid

Answer 9

one glycerol bonded to 2 fatty acid tails and a phosphate group

Question 10

what is a special property of the phosphate group of phospholipids

Answer 10

hydrophilic

Question 11

what is the main function of triglycerides in animals and plants

Answer 11

energy storage

Question 12

why do the fatty acid tails of lipids make them a good energy storage

Answer 12

bonds contain lots of chemical energy which is released when broken down

Question 13

why is it important that triglycerides are insoluble

Answer 13

do not affect osmosis and water potential

Question 14

how do mammals store triglycerides

Answer 14

store triglycerides as oil droplets in adipose tissue to help them survive when food is scarce (e.g. hibernating bears)

Question 15

why might triglycerides be better suited to energy storage than carbohydrates

Answer 15

fats have more carbon-carbon bonds + carbon-hydrogen bonds
they contain more energy per molecule so more energy stored in less space

Question 16

how can triglycerides be used in respiration

Answer 16

fatty acids have long carbon chains which can be broken down to release acetyl groups for the krebs cycle

Question 17

what are other useful properties of triglycerides

Answer 17

thermal insulation: in adipose tissue just below the skin

electrical insulation: myelin sheath speeds transmission

buoyancy: allows animals to float

protection

Question 18

what is the function of phospholipids

Answer 18

form the phospholipid bilayer of cell membranes

Question 19

how do phospholipids form the phospholipid bilayer

Answer 19

phospholipid heads are hydrophilic and the tails are hydrophobic, heads face out towards water on both sides and tails face inwards

Question 20

how does the phospholipid bilayer act as a barrier

Answer 20

the hydrophobic tails facing inwards prevent water soluble substances entering

Question 21

what is the role of cholesterol

Answer 21

impacts fluidity of the membrane

Question 22

how does the small size of cholesterol impact its function

Answer 22

enables it to fit tightly inbetween phospholipids

Question 23

how does cholesterol act at high temperatures

Answer 23

bind to hydrophobic tails, making them pack more closely to reduce fluidity

Question 24

how does cholesterol act at lower temperatures

Answer 24

prevents phospholipids packing too closely and increases fluidity