lipids

Question 1

describe the structure of a phospholipid

Answer 1

2 fatty acid tails
glycerol
phosphate head

Question 2

describe the phosphate in a phospholipid

Answer 2

hydrophilic
- attracts water

Question 3

describe the fatty acids in a phospholipid

Answer 3

hydrophobic
- repels water

Question 4

how do phospholipids act as a barrier?

Answer 4

• part of cell surface membrane
• hydrophobic core is created when a phospholipid bilayer forms
• prevents water soluble substances getting through

Question 5

state 3 functions of phospholipids

Answer 5

• acts as a barrier
• holds proteins in membrane but allows some movement due to weak hydrophobic interactions
• separates external environment from aqueous cytoplasm

Question 6

how are lipids joined?

Answer 6

ester bonds

Question 7

what does saturated mean?

Answer 7

no double bonds free

Question 8

what does unsaturated mean?

Answer 8

double bonds free

Question 9

if the fatty acid tail is saturated, what does this mean for the membrane?

Answer 9

less fluid

Question 10

if the fatty acid tail is unsaturated, what does this mean for the membrane?

Answer 10

more fluid

Question 11

describe the structure of a triglyceride

Answer 11

• 3 fatty acids
• glycerol
• ester bonds
• formed during condensation reactions
• insoluble

Question 12

what happens when double bonds are present in fatty acids? (unsaturated)

Answer 12

• kinks occur
• causes chain to bend
• cannot pack closely and become liquid

Question 13

state 4 roles of triglycerides

Answer 13

• energy source
• insulation
• buoyancy
• protection

Question 14

how do triglycerides provide energy?

Answer 14

3 fatty acids which are dense with energy are broken down via beta oxidation and the energy is released

Question 15

how do triglycerides provide insulation?

Answer 15

traps air under skin and around vital organs, reducing heat loss

Question 16

how do triglycerides provide buoyancy?

Answer 16

they are hydrophobic, repelling water for aquatic animals

Question 17

how do triglycerides provide protection?

Answer 17

absorbs impact around vital organs

Question 18

describe how an ester bond is formed

Answer 18

• esterification
• glycerol and 3 fatty acids undergo a condensation reaction
• 3 water molecules removed
• bond forms between fatty acid carboxyl and glycerol hydroxyl

Question 19

what is a sterol?

Answer 19

an alcohol with a hydroxyl group

Question 20

describe the structure of cholesterol

Answer 20

• 4 carbon rings
• small and narrow
• located between fatty acid phospholipid tails
• hydrophilic and hydrophobic regiosn

Question 21

describe the function of cholesterol

Answer 21

• stabilises membrane structure
• maintains fluidity and temperature
• produces steroid hormones which pass through bilayer to reach receptors