2.4- Lipids

Question 1

What are lipids composed of?

Answer 1

hydrocarbon chains (fatty acids)

or

rings (steroids

Question 2

Beneficial biological consequences of lipids?

Answer 2

waxes
- prevent water loss from leaves
- waterproof feathers in birds

phospholipids
- provide structural framework for cells

lipids
- help the body absorb fat-soluble vitamins (eg, A + D)

Question 3

Detrimental biological consequences of lipids

Answer 3

lipoproteins
- digested fats are hard to transport and require a protein coat

steroid hormones
- req carrier proteins to move through the bloodstream

Question 4

What does it mean when lipids are amphipathic?

Answer 4

have both non polar and polar components

Question 5

Structure of a phospholipid

Answer 5

Polar phosphate head, glycerol neck, fatty acid tail

Question 6

What are the three main groups of lipids?

Answer 6

simple lipids

compound lipids

derived lipids

Question 7

What are simple lipids

Answer 7

esters of fatty acids and alcohol

Question 8

What are examples of simple lipids?

Answer 8

waxes- waterproofing
triglycerides- energy storage + insulation

Question 9

What are compound lipids

Answer 9

esters of fatty acids and alcohol linked to an additional group

Question 10

What are examples of compound lipids

Answer 10

phospholipids- linked to phosphate used in cell membranes

glycolipids- linked to carbohydrate, used in cell-cell interactions

Question 11

What are derived lipids

Answer 11

the hydrolysis of simple or compound lipids

Question 12

What are examples of derived lipids

Answer 12

steroids, cholesterol

Question 13

What are fatty acids linked to in alcohols?

Answer 13

hydroxyl -OH group.

Question 14

What are fatty acids joined by

Answer 14

condensation reactions that produce an ester linkage

Question 15

Triglyceride lipid formation via condensation reactions

Answer 15

3 fatty acids + glycerol
produces 3 water molecules

Question 16

Phospholipid lipid formation via condensation reactions

Answer 16

2 fatty acids + glycerol + phosphate group
produces 2 water molecules

Question 17

Three types of saturation of fatty acids

Answer 17

saturated
monounsaturated
polyunsaturated

Question 18

What is saturation determined by?

Answer 18

number of double bonds

saturated = 0 double bond
monoun= 1
polyun= 2+

Question 19

Compare and contrast cis-isomer vs trans-isomer

Answer 19

Cis-isomer
H\C = C/ H
common in nature
H atoms ont he same side
double bond causes a bend
loosely packed
triglycerides with cis-isomers have low melting points

Trans-isomer

H
\C=C\
H

rare in nature, only produced by ruminant animals
produced artificially to make solid fats
H atoms on different sides
double bond does not cause a bend
closely packed
triglycerides with trans-isomers have high melting points

Question 20

What determines how orgamisms store lipids?

Answer 20

the type of fatty acid

Question 21

What are saturated fatty acids stored as

Answer 21

fats

Question 22

What are cis-unsaturated fatty acids stored as

Answer 22

oils

Question 23

Compare and contrast fats vs oils lipid storage

Answer 23

Fats
animal source (endoderms)
saturated fatty acids
No double carbon bonds -> straight chains
solid at room temp
high melting points

Oils
plant source
unsaturated fatty acids
Have double carbon bonds therefore forming bent chains
liquid at room temp
low melting points

Question 24

Lipid storage in Animals

Answer 24

endotherms (warm blooded mammals) produce more saturated fats because the higher body temperatures keep it liquid.

Ectotherms produce cis-unsaturated oils as saturated fats solidify in the colder temperatures.

Question 25

What is a source of poly-unsaturated fats that are essential to a human diet?

Answer 25

cold water fish oils, omega 3 and 6

Question 26

Lipid storage in plants

Answer 26

mostly produce cis-unsaturated liquid oils tropical plants tend to produce more saturated fats than temperate plants

Question 27

Lipid functions

Answer 27

Energy storage Thermal insulation Structural component Communication

Question 28

Example of lipids used for energy storage

Answer 28

triglycerides in adipose tissue are used for long-term energy storage because: - lipids are more difficult to digest than carbohydrates - lipids store 2x energy per gram than carbs Triglycerides can be hydrolysed to produce ATP via aerobic cellular respiration Adipose tissue is found under the skin and around organs

Question 29

Example of lipids for thermal insulation

Answer 29

blubber Triglycerides have a low thermal conductivity (limited capacity to conduct heat) Mammals in cold environments such as the ringed seal have thick layers of subcutaneous fat to insulate the internal organs against the cold.

Question 30

Example of lipids for structural components

Answer 30

phospholipids in the bilayer

Question 31

Example of lipids for communication

Answer 31

steroid hormones like oestradiol and testosterone used as signalling molecules

Question 32

Where is adipose tissue found

Answer 32

Adipose tissue is found under the skin and around organs

Question 33

Why don't humans use layers of subcutaneous fats to insulate

Answer 33

high levels of fat cause obesity and increase retention of heat which increases susceptibility to heat stress

Question 34

What are steroids

Answer 34

derived lipids composed of four fused carbon rings

Question 35

Describe steroids

Answer 35

non-polar hydrophobic- needs a carrier protein (albumin) to be transported in the blood lipophilic- freely diffuse across the bilayer into cells

Question 36

Outline the role of condensation and hydrolysis in the relationship between fatty acids, glycerol and triglycerides. [6]

Answer 36

Answer: hydrolysis: [3 max] when larger molecules are broken to smaller molecules/subunits; with the addition of water; fatty acids produced by the hydrolysis of fats/triglycerides; breaking of ester bonds; with release of glycerol; condensation: [3 max] when molecules/subunits are joined to form a larger molecule; water formed/removed; fatty acids linked to glycerol; up to three fatty acids can be linked to each glycerol; through formation of ester bonds;