lipids (h,i,j) Flashcards
1
Q
What is a macromolecule?
A
- complex structures with a relatively large molecular mass.
- examples are triglycerides and phospholipids
2
Q
what is a triglyceride and its structure?
A
- a lipid containing 1 glycerol molecule and 3 fatty acids
- glycerol = alcohol, -OH
- fatty acids = carboxylic acids, -COOH
3
Q
how are triglycerides formed?
A
- hydroxyl groups on the fatty acids interact with the hydrogen on the glycerol to form 3 water molecules and ester bonds, -COO
- esterification (type of condensation reaction)
- the reverse hydrolysis requires 3 water molecules
4
Q
describe fatty acids’ structure
A
- fatty acid tails are hydrophobic - they repel water and are thus insoluble in it
- fatty acids have the same basic structure but differing hydrocarbon tails
5
Q
what are saturated lipids?
A
- no double bonds between their carbon atoms, in the hydrogen tail, only single bonds
- ‘saturated’ with hydrogen
- e.g. saturated fats
6
Q
what are unsaturated lipids?
A
- have at least one double bond between carbon atoms, which cannot pack so closely together, causing the chain to kink
- monounsaturated (one double bond) and polyunsaturated (multiple double bonds)
- liquid at room temperature
- e.g. oils
7
Q
function of triglycerides
A
- in plants and animals and some bacteria they are used as energy storage molecules
8
Q
Why are triglycerides good for storage? (how structure links to the function)
A
- the long hydrocarbon tails of the fatty acids contain lots of chemical energy - lots is released when they are broken down
- they are insoluble so do not cause water to enter the cell by osmosis, which would make them swell. triglycerides bundle together as insoluble droplets in cells because of hydrophobic fatty acid tails - tails face inwards, shielding themselves from water with their glycerol heads
9
Q
What is a phospholipid and its structure?
A
- contain P as well as C,H,O
- 2 fatty acids, 1 phosphate group and a glycerol molecule
- inorganic phosphate ions found in the cytoplasm of every cell, PO₄³⁻ - have extra electrons = negatively charged = soluble in waters
10
Q
Function of phospholipids
A
- found in cell membranes of all eukaryotes and prokaryotes, making up the phospholipid bilayer
- thus help cell-surface membranes control what substances enter and leave a cell
11
Q
How does the structure of phospholipids link to its function?
A
- phospholipid charged heads are hydrophilic + their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side
- the centre of the bilayer is hydrophobic, so water-soluble substances cannot easily pass through it; the membrane acts as a barrier to those substances.
- they are able to separate an aqueous environment in which cells usually exist from the aqueous cytosol within cells.
12
Q
Describe sterols
A
Complex alcohol molecules based on a 4 carbon ring structure with a hydroxyl (OH) group at one end. Steroid alcohols.
13
Q
What is cholesterol?
A
- a sterol
- a lipid found in cells
- have hydrophilic/hydrophobic characteristics
- hydroxyl group = polar + hydrophilic, rest = hydrophobic
14
Q
How does the function of cholesterol link to its structure?
A
- small size and flattened shape = allows cholesterol to fit between the phospholipid molecules in the membrane
- they bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together, helping make the membrane less fluid and more rigid
15
Q
What are the roles of lipids?
A
- membrane formation and creation of hydrophobic barriers
- hormone production
- electrical insulation
- waterproofing
