lipids

Question 1

describe the test for lipids (2)

Answer 1

• add ethanol and shake
• add water and shake
• forms a milky emulsion

Question 2

why are lipids not polymers

Answer 2

they don’t have repeating monomer units

Question 3

describe the structure of a triglyceride molecule (1)

Answer 3

• glycerol molecule
• 3 fatty acid chains

Question 4

what is an ester bond

Answer 4

a covalent bond formed between the OH of a glycerol molecule and the OH of a fatty acid in a condensation reaction

Question 5

how many ester bonds are in a triglyceride

Answer 5

3

Question 6

are fats solid or liquid at room temperature

Answer 6

solid e.g. butter
saturated, C-C

Question 7

are oils solid or liquid at room temperature

Answer 7

liquid e.g. olive oil
unsaturated, C=C

Question 8

what is a saturated fatty acid

Answer 8

fatty acid chain with no double carbon bonds (doesn’t include the carboxyl group)

Question 9

define monoUNsaturated

Answer 9

fatty acid with one double carbon bond

Question 10

define polyUNsaturated

Answer 10

fatty acid with multiple double carbon bonds

Question 11

why are unsaturated triglycerides liquids at room temperature?

Answer 11

• they contain double carbon bonds
• double carbon bonds cause fatty acid tails to bend
• triglyceride molecules are further apart
• intermolecular force of attraction decreases, molecule is less compact
• less energy to overcome so it is liquid at room temperature

Question 12

why are saturated triglycerides solid at room temperature?

Answer 12

• no double carbon bonds
• fatty acid tails don’t bend
• less space between molecules so stronger intermolecular forces of attraction
• more energy to overcome so solid at room temperature

Question 13

why do triglycerides release lots of energy

Answer 13

there are lots of carbon-hydrogen bonds, these release energy when they break

Question 14

why are triglycerides a good water source

Answer 14

they release water when they are broken down in respiration

Question 15

are triglycerides polar or non-polar?

Answer 15

non-polar so they are insoluble
- don’t affect osmosis in cells

Question 16

give 3 uses of lipids

Answer 16

• aquatic animals produce oil to waterproof their fur
• thermal & electrical insulation
• buoyancy

Question 17

how are lipids like proteins?

Answer 17

they have a constant region (glycerol) and a variable region (fatty acid)

Question 18

Describe the structure of a phospholipid (1)

Answer 18

• glycerol
• 2 fatty acids
• phosphate group

Question 19

how does a phosphate group join a glycerol molecule

Answer 19

• condensation reaction
• between OH on glycerol and OH on phosphoric acid
• creates a phosphate ester bond

Question 20

is the phospholipid head hydrophobic or hydrophilic?

Answer 20

hydrophilic
- has a negative charge
- attracts H+ in water

Question 21

what are micelles

Answer 21

circular formations that are made up of phospholipid tails

Question 22

describe phospholipid bilayer

Answer 22

• hydrophilic heads face outwards towards the water
• hydrophobic tails face inwards away from water

Question 23

how are membranes fluid

Answer 23

because phospholipids can move around each other- allows the cell to change shape

Question 24

give 2 roles of the bilayer

Answer 24

• controls what leaves/ enters the cell
• electrical insulation- does not let ions or water in as the fatty acid tails are hydrophobic and non-polar

Question 25

give 5 functions of lipids

Answer 25

- phospholipids provide flexibility to membranes -thermal insulation- slow conductors of heat and retain body heat -electrical insulation- in myelin sheath around nerve cells -protection- fat around organs such as kidney -insoluble- used for waterproofing, waxy lipid cuticle to prevent water loss -energy source- when oxidised they release energy

Question 26

describe 2 features which make lipids suitable for their function

Answer 26

- lots of energy stored in a small mass- good for animals as they can reduce the mass they carry around -lots of energy stored in C-H bonds - they are large and non-polar so insoluble and dont affect water potential so no bursting -release water when oxidised so act as a water source

Question 27

what is the difference between a phosphate molecule and a fatty acid molecule

Answer 27

phosphate is hydroPHILIC and attracts water fatty acid is hydroPHOBIC and repels water

Question 28

describe the structure of a phospholipid

Answer 28

- hydrophilic head- attracts water -hydrophobic tail- repels water

Question 29

describe a control that could be used during a test for lipids

Answer 29

- instead of adding ethanol and water to the sample, replace the sample with water - solution should stay clear

Question 30

list 2 differences between a triglyceride molecule and a phospholipid molecule (2)

Answer 30

1. triglyceride has 3 fatty acids 2. phospholipid has 2 fatty acids, 1 phosphate group or 1. triglyceride is non polar 2. phospholipid is polar

Question 31

explain why phospholipids form a bilayer but triglycerides don't (3)

Answer 31

- phospholipids have both hydrophobic and hydrophilic regions - triglycerides are just hydrophobic- non-polar - phospholipid heads attract to water, fatty acid tails repel water

Question 32

compare and contrast the structure and properties of triglycerides and phospholipids (5)

Answer 32

- both have glycerol - both have ester bonds - triglycerides have 3 fatty acids, phospholipids have 2 fatty acids and a phosphate group - both are insoluble in water - triglycerides are non-polar and phospholipids have hydrophilic and hydrophobic regions - both have C,H,O but phospholipids also have P