Biological Molecules - Lipids

Question 1

Functions of lipids

Answer 1

• integral part of cell membranes + used as an energy store
• plants + animals convert spare food into oils/fats when needed - for energy
  -insulation(thermal and mechanical) - cushioning organs and keep us warm
• source of enrgy/energy store
• waterfproofing + floating - has a low density(floating)
• some lipids are hormones

Question 2

Fats vs Oils

Answer 2

Fats are solids at room temp
Oils are liquids at room temp
both fats and oils made up of organic chemicals fatty acids and glycerol combined using ester bonds.
animals produce motsly fat and plants produce mostly oil.
both triglycerides.
Glycerol chemical formula = C3H8O3

Question 3

elements in lipids

Answer 3

carbon, hydrogen, oxygen
contain considerably LOWER proportion of oxygen than carbohydrates.
much HIGHER proportion of hydrogen than carbs - H,H - higher hydrogen. More hydrogen atoms = more energy ( C-H is the bond which stores energy)

Question 4

Fatty acids

Answer 4

all fatty acids have a long hydrocarbon chain with a carboxyl group at one end
Living tissues contain 70 diff kinds of fatty acids

Question 5

How do fatty acids vary?

Answer 5

• Length of the carbon chain(usually 15-17 carbon atoms long in organisms)
• may be saturated or unsaturated

Question 6

Saturated fatty acid

Answer 6

Each carbon atom is joined to the carbon atom next to it by single covalent bond – stearic acid

Question 7

Unsaturated fatty acid

Answer 7

Carbon chains have one or more double COVALENT bonds
The double bond kinks the chain
There are 1 or more fatty acids with a carbon-carbon double bond so only 1 spare link to hydrogen.
Two types – monounsaturated and polyunsaturated.

Question 8

Monounsaturated vs polyunsaturated fatty acids

Answer 8

Monounsaturated - 1 double bonds
Polyunsaturated - more than 1 double bond
– Linoleic acid(polyunsaturated)

Question 9

Essential fatty acid

Answer 9

• cannot make from other chemicals
• must be obtained from diet

Question 10

lipids properties

Answer 10

• insoluble in water
• soluble in Non-Polar solvents

Question 11

Esterification

Answer 11

Formation of ester bonds
A bond is formed in a condensation reaction between the carboxyl group of the fatty acid and one hydroxyl group from the glycerol
- a molecule of water is removed and the remaining bond is known as an ester bond

Question 12

nature of the lipid

Answer 12

nature of lipid formd depends on the fatty acids which are present
lipids containing saturated fatty acids more likely to be solids at room temp than lipid which contains unsaturated fatty acids.

Question 13

Fatty acid diagram - general formula

Answer 13

O
||
R ____C____OH

R represent hydrocarbon chain.

Question 14

Ester bond

Answer 14

O
||
O____C

Question 15

LIPIDS AND ENERGY

Answer 15

Lipids contain many carbon-hydrogen bonds
When lipids are oxidised in respiration then these carbon-hydrogen bonds are broken down to form carbon dioxide and water.
The reaction(respiration - breaking bonds of lipids) is used to drive the production of a lot of ATP.
Lipids esp triglycerides store about three times as much energy as the same mass of carbohydrates.

Question 16

The nature of lipids

Answer 16

 Lipids contain many carbon hydrogen bonds and little oxygen
 When these are oxidised in respiration the carbon hydrogen bonds are broken into carbon dioxide and water of the ultimate product. This reaction is used to drive the production of a lot of ATP.
 Lipids, especially triglycerides store about three times as much energy as the same mass of carbohydrates would

Question 17

Hydrophobic nature of lipids and how this helps them with waterproofing

Answer 17

E.g. Oils are important for waterproofing the fur and feathers of mammals + birds
and insects+plants use waxes
Hydrophobic means water-repelling –> waterproof

Question 18

Lipids as good insulators

Answer 18

• a fatty sheath insulates nerves so that nerve impulses can travel faster
• insulate animals against heat loss - like they thick layer of blubber in whales

Question 19

What is the significance of lipids having a low density?

Answer 19

The body fat of water mammals will allow them to float easily

Question 20

Why don’t lipids interact w reactions in the cytoplasm?

Answer 20

Lipids can dissolve in non-polar solvent but not water. Lipids dont interact with the water-based reaction which go on in cytoplasm of cell

Question 21

What is a phospholipid?

Answer 21

Inorganic phosphate ions in cytoplasm. Phosphate group sometimes undergoes esterification reaction with the hydroxyl group of a glycerol. so then phospholipid is formed
A phospholipid is a lipid that contains a phosphate group and is a major part of cell membranes. A phospholipid consists of a hydrophilic (water-loving) head and hydrophobic (water-fearing) tail (see figure below). The phospholipid is essentially a triglyceride in which a fatty acid has been replaced by a phosphate group of some sort.

Question 22

Properties of a phospholipid

Answer 22

• the two fatty acid chains of a phospholipid are neutral and insoluble in water
• the phosphate head(PO4^3-) has a small NEGATIVE electrical charge (attracted to small positive electricalcharge on of hydrogen atoms in water molecules)and it is soluble in water
  so this means that when phospholipids come in contact w water 2 parts of molecule behave very differently.

Question 23

Diagram of phospholipid

Answer 23

Phosphate group
|
Glycerol
| |
fatty fatty
acid acid

Question 24

phospholipid in the water

Answer 24

Phosphate part is hydrophilic and dissolves readily in water because it is polar.
Lipid tails are hydrophobic and do not dissolve in the water.

If molecules are tightly packed they may form a monolayer - with the hydrophilic heads in the water and the hydrophobic tails sticking out of the water

Question 25

The types of formations phospholipids take in water

Answer 25

Monolayer - single-closely packed layer of phospholipids. The hydrophilic phosphate heads heads in the water and the hydrophobic tails in the air.
Micelle - all the hydrophobic tails are pointing inside and all the hydrophilic tails are pointing outside — general circle shape,
Bilayer - more common in cells. Where there are water-based solutions on either side of the membranes. 2 layers with the hydrophilic tails pointing towards the water and the hydrophobic tails pointing towards the middle.

Question 26

What is the unit membrane?

Answer 26

A bilayer structure that is formed when the phospholipids are in an aqueous environment. Hydrophobic tails on inside and hydrophilic heads on outside(bilayer).

Question 27

permeability of unsaturated fatty acids

Answer 27

more permeable.
have at least 1 carbon double bond which KINKS the chain and this means that there is a larger distance between the molecules and so there are weaker intermolecular forces of attraction which means that it is easier to separate the fatty acids. lower melting point as a result. + more permeable.

Question 28

are fatty acids polar or non-polar?

Answer 28

nonpolar.
anyhting hydrophilic struggles to get through the phospholipid bilayer.

Question 29

Nature + function of lipids

Answer 29

• Often used as energy stores in living organisms
• insulation of organs + electric insulator - myelin sheath
• low density of fat makes it easier for animals to swim e.g whales/polar bears have a layer of adipose tissue beneath their skin
• waterproofing - oils for coating the fur and feathers of birds/mammal and insects and plants use waxes
• cells in human tissue(adipose) filled w globules of triglycerides
• stored triglycerides provide a place in which fat-soluble vitamins can be stored
• dont affect water potential

Question 30

permeability of phospholipid bilayer

Answer 30

lipids are non-polar so can easily pass through phospholipid bilayer - why absorbed easily into skin

Question 31

what happens to lipids during respiration

Answer 31

they are hydrolysed.
oxidised so the carbon-hydrogen bonds break to give co2 and water - this reaction used to drive production of ATP.

Question 32

permeability of saturated fatty acids

Answer 32

less permeable.
fatty acids are more closely packed together because there are no carbon carbon double bonds to cause a kink in the chain. - stronger intermolecular forces of attraction so less permeable + higher mp.

Question 33

Cholesterol

Answer 33

not formed from fatty acids and glycerol
samll molecule made from 4 carbon based rings
strcuture formed from these 4 rings are called steroids e.g. hormones - testosterone and oestrogen
Cholesterol = major part of cell membranes where it helps to regulate permeability of membrane