Lipids

Question 1

8 functions of lipids

Answer 1

electrical insulation
thermal insulation
cell membrane structure
energy store
waterproofing
source of metabolic water
buoyancy
protection

Question 2

chemical elements of lipids

Answer 2

carbon, hydrogen, oxygen

Question 3

solubility of lipids

Answer 3

insoluble in water
soluble in organic solvent (e.g. ethanol)

Question 4

5 examples of lipids

Answer 4

triglycerides (all fats and oils)
phospholipids
waxes
steroids
cholesterol

Question 5

lipids as electrical and thermal insulation

Answer 5

electrical: around neurons
thermal: adipose tissue under skin surface

Question 6

lipids in cell membrane structure

Answer 6

phospholipid bilayer and cholesterol

Question 7

lipids as an energy store

Answer 7

stored as droplets in the cytoplasm as they are compact and insoluble
have have a high energy yield –> 2x energy released compared to carbohydrates

Question 8

lipids in waterproofing

Answer 8

leaf cuticles/fur/feathers/skin

Question 9

lipids as a source of metabolic energy

Answer 9

can respire fats to release water

Question 10

lipids in buoyancy

Answer 10

lipids are less dense than water so help with floating and swimming

Question 11

lipids as protection

Answer 11

subcutaneous fat around major organs

Question 12

simple lipids + e.g.

Answer 12

only glycerol and fatty acids –> triglycerides

Question 13

compound lipids + e.g.

Answer 13

glycerol, fatty acids and a molecule, group or compound –> phospholipids

Question 14

why are lipids not polymers?

Answer 14

they are made of monomers, but their monomers are not repeated, just joined

Question 15

chemical formula and structure of glycerol

Answer 15

C3H8O3
3 carbons, each with a hydrogen and hydroxyl group. end carbons have 2 hydrogens

Question 16

state and explain the chemical formula for a general fatty acid

Answer 16

CH3(CH2)nCOOH
CH3 and carboxyl group, with a variable group (R group) in the middle: any number of Cs bound to 2 Hs

Question 17

ester bond

Answer 17

covalent bond between a fatty acid and glycerol.

Question 18

saturated fatty acid

Answer 18

have a full complement of Hs in hydrocarbon tail –> no C=C in hydrocarbon tail.
higher melting point
solid at room temp

Question 19

unsaturated fatty acid

Answer 19

don’t have full complement of H
have at least one C=C in hydrocarbon tail
lower melting point
liquid at room temp

Question 20

polyunsaturated

Answer 20

more than one C=C in hydrocarbon tail

Question 21

respiratory substrate

Answer 21

a molecule that can release energy to form ATP, which animals oxidise

Question 22

oxidise

Answer 22

break down in the presence of oxygen

Question 23

how is energy released from RS substrates?

Answer 23

from breaking C-C and C-H bonds

Question 24

why can more energy be released for respiring lipids than carbohydrates?

Answer 24

lipids have many more C-C and C-H bonds (in their R group)

Question 25

describe the structure of a tiglyceride

Answer 25

1 molecule of glycerol attached to three fatty acid tails joined by ester bonds

Question 26

describe the structure of a phospholipid

Answer 26

1 molecule of glycerol with a phosphate group attached and 2 fatty acid tails joined to it by ester bonds