2.2 Lipids

Question 1

what are lipids

Answer 1

Group of substances that contain high number of carbon + hydrogen atoms but a low number of oxygen. They are insoluble in water as they are non-polar but are soluble in alcohol

Question 2

why aren’t they polymers

Answer 2

made from different compounds

Question 3

What are triglycerides

Answer 3

A Type of lipid that’s made up of glycerol and 3 fatty acids that are bonded to the glycerol

Question 4

what is glycerol

Answer 4

An alcohol that contains 3 carbon atoms and has 3 -OH groups

Question 5

what are fatty acids

Answer 5

A chain of hydrocarbons with (COOH) attached to one end. Carbon atoms are even number

Question 6

why is the structure of fatty acids acidic

Answer 6

The carboxyl group is ionised into the H+ and COO- group. The release of H+ makes it acidic

Question 7

What happens if a fatty acid is monounsaturated or polyunsaturated

Answer 7

produces a kink wherever the double bond is

Question 8

What does the kink do

Answer 8

The kink pushes the molecules apart which makes them more fluid

Question 9

What is an ester bond

Answer 9

A covalent bond formed by a condensation reaction between the -OH of the carboxyl group and -OH group of the alcohol

Question 10

5 functions of triglycerides

Answer 10

1) Energy Source: Can be broken down in respiration to release energy + generate ATP. The first step is to hydrolyse the ester bond and then fatty acid + glycerol can be broken into CO2 and H20
2) Energy Store: insoluble in water so they can store energy without affecting water potential
3) Insulation: Adipose tissue is a storage location for lipids in whales acting as a thermal insulator. Lipids in nerve cells can act as electrical insulators
4) Buyancy: As fat is less dense than water it’s used by aqautic mammals to keep them afloat
5) Protection: Humans have fat around delicate + important organs to act as shock absorbers. The peptidoglycan cell wall of some bacteria is covered in lipid rich outer coat

Question 11

What is a phospholipid

Answer 11

Type of lipid which contains a glycerol that’s bonded to 2 fatty acids as well as a phosphate group

Question 12

What is a phosphate ester bond

Answer 12

When a condensation reaction takes place between glycerol and phosphate group

Question 13

What happens to phospholipid when reacting with water

Answer 13

When surrounded by water hydrogen atoms disassociate themselves from phosphate group

Question 14

what is the head of phospholipid

Answer 14

phosphate group + glycerol

Question 15

what is the tail of phospholipid

Answer 15

the fatty acids

Question 16

what does hydrophilic mean and which part is it

Answer 16

A hydrophilic is a molecule that is attracted to water due to it having a charge . The head is hydrophilic

Question 17

what does hydrophobic mean and which part is it

Answer 17

molecule that’s repelled by water due to it not having a charge. The tail is hydrophobic

Question 18

what does amphipathic mean

Answer 18

molecule that has both polar & non-polar regions. (head=polar while the tail=non-polar)

Question 19

what is a phospholipd bilayer

Answer 19

a bilayer is formed when 2 layers of phospholipid tails (hydrophobic) point each other inwards while 2 rows of phopholipid heads (hydrophilic) are outwards and pointed away from each other.

Question 20

how is the membrane selectively permeable

Answer 20

only allows small + non-polar molecules to move through the tail bilayer

Question 21

what is cholesterol and structure

Answer 21

• comes from sterol family ( type of lipid which isn’t made from glycerol or fatty acids)
• consists of 4 carbon based rings
• contains hydroxyl group making it hydrophobic which allows it to sit between hydrophobic section

Question 22

role of cholesterol

Answer 22

• regulates fluidity of membrane to prevent it becoming too stiff or too fluid
• Cholesterol creates testosterone , oestrogen and vitamin D

Question 23

why can they pass through the bilayer and other membranes

Answer 23

Since they are small + hydrophobic they can pass through bilayer and other membranes of the cell