lipids and cell membrane

Question 1

what do lipids consists of?

Answer 1

fatty acids

Question 2

what are the two groups of lipids?

Answer 2

phospholipids and triglycerides

Question 3

why can’t lipids form polymers?

Answer 3

as they do not have monomers as they have different base units instead

Question 4

what are the types of lipids?

Answer 4

fats, seeds, oils and steroids

Question 5

what are some properties of lipids?

Answer 5

• insoluble in water as fatty acids are hydrophobic and doesn’t affect water potential
• soluble in organic solution (ethanol)
• solidify at 20°C

Question 6

what are lipids hydrolysed by?

Answer 6

lipase

Question 7

what are some uses/function of lipids?

Answer 7

–> protection
- a layer to protect organs
–> insulation
- blubber (insulated from cold weather)
–> waterproofing
- plants, waxy cuticle
- animals, oils from sebaceous glands
–> energy source
- 1g of fat releases more than 1g of a carbohydrate

Question 8

what are triglycerides made out of?

Answer 8

3 fatty acids and glycerol

Question 9

how is a triglyceride formed?

Answer 9

• by a condensation reaction forming an ester bond between 3 fatty acids and glycerol
• 3 hydroxyl group from glycerol and hydroxyl group of each fatty acids

Question 10

how many water molecules are lost during a condensation reaction to form a triglyceride?

Answer 10

3

Question 11

what is the general formula for every fatty acid?

Answer 11

RCOOH
- R group (hydrocarbon chain)
- carboxyl group

Question 12

what is a saturated fatty acid?

Answer 12

where the fatty acid only contains single carbon bonds

Question 13

what is a unsaturated fatty acid?

Answer 13

• where the fatty acid only contains double carbon bonds
• so there are fewer hydrogen atoms
• causing the chain to bend

Question 14

describe the method of the biochemical test for lipids

Answer 14

1. crush up sample with pestle and mortar
2. add water and ethanol
3. shake for 2 mins
4. pour into water
5. If a positive result, should form a cloudy emulsion.

Question 15

what are phospholipids made out of?

Answer 15

2 fatty acids + glycerol and a phosphate group

Question 16

what are the properties of a phospholipid?

Answer 16

• they have a hydrophilic head (phosphate group)
• they have a hydrophobic tails (fatty acids)

Question 17

how is a phospholipid formed?

Answer 17

• by a condensation reaction forming an ester bonds between 2 fatty acids + glycerol + phosphate group
• 2 hydroxyl group from glycerol and 2 hydroxyl group of each fatty acids and phosphate group

Question 18

what is the cell membrane made out of and why?

Answer 18

phospholipids as it doesn’t allow polar molecules and ions through

Question 19

what is a cell membrane?

Answer 19

it is partially permeable and controls the substances coming in and out the cell

Question 20

what does the phospholipid form in a cell membrane?

Answer 20

bilayer and arranged in a fluid mosaic structure

Question 21

what is a fluid mosaic structure?

Answer 21

where the phospholipids can still move with another neighbouring phospholipid but there are proteins that are scattered

Question 22

what is a glycoprotein?

Answer 22

a carbohydrate that is attached to a protein

Question 23

what is a glycolipid?

Answer 23

a carbohydrate that is attached to a lipid

Question 24

what is the function of a glycoprotein and glycolipid?

Answer 24

acts as an receptor, antibodies and used for cell adhesion

Question 25

what is the function of a peripheral protein?

Answer 25

acts as an receptor, which detects chemicals to be released for a response

Question 26

what is cholestrol?

Answer 26

a type of lipid

Question 27

what is the function of the cholestrol?

Answer 27

-provides stability which binds to the tails of the phospholipids - regulates the fluidity of cell membrane

Question 28

what is the function of the protein channel and channel?

Answer 28

allows larger molecules, polar molecules and ions through the cell membrane

Question 29

what are the factors that affect cell membrane permeability?

Answer 29

temperature and solvents

Question 30

how does temperature affect membrane permeability?

Answer 30

- by increasing the temp, the phospholipid have more ke, they move faster, so the membrane increases in permeability - at high temp, proteins denature and the water in the cell expands increasing the pressure of the cell membrane which increases permeability

Question 31

how does solvents affect membrane permeability?

Answer 31

- non polar solvents (alcohols+acetone) can insert themselves in bilayer - can form hydrogen bonds near the ester bonds - this pushes the phospholipids out of place - this increases movement and increases permeability OR - solvent denatures disrupting bonds moving phospholipids out of place