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 acid tails 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

how are lipids joined?

Answer 5

ester bonds

Question 6

state 3 functions of phospholipids

Answer 6

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

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

describe the structure of a triglyceride

Answer 10

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

Question 11

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

Answer 11

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

Question 12

state 4 roles of triglycerides

Answer 12

• energy source
• insulation
• buoyancy
• protection

Question 13

how do triglycerides provide energy?

Answer 13

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

Question 14

how do triglycerides provide insulation?

Answer 14

they are hydrophobic, repelling water for aquatic animals

Question 15

describe how an ester bond is formed

Answer 15

• hydroxyl groups on fatty acids and glycerol interact
• forming 3 water molecules (condensation reaction)
• process is esterification.

Question 16

what is a sterol

Answer 16

• complex alcohol molecule
• with 4C ring structure

Question 17

describe the structure of cholesterol

Answer 17

• hydroxyl group is attracted to phosphate heads
• carbon rings attracted to hydrophobic tails
• fits between phospholipids + prevents them aligning too closely & holds them together at the same time

Question 18

what would happen to the pH of a solution when triglycerides are digested?

Answer 18

• the fatty acids are free from the ester bond
• so will lower the pH as they are acids

Question 18

describe the function of cholesterol

Answer 18

helps strengthen cell membrane by interacting with the phospholipid bilayer and maintains fluidity

Question 19

describe the difference between a phospholipid and a triglyceride

Answer 19

• tri contain 3 fatty acids, phos contain 2 fatty acids
• tri non-polar, phos have a polar head and non-polar fatty acid tails