bye later ( phospholipid)

Question 1

is the phosphate head hydrophobic or hydrophilic

Answer 1

hydrophilic

Question 2

is the hydrocarbon tail hydrophobic or hydrophilic

Answer 2

hydrophobic

Question 3

what is the cell surface membrane

Answer 3

forms a boundary between the cell cytoplasm and the outside environment. it allows different condition to be established inside and outside of the cell and controls the movement of substances inside and outside of the cell

Question 4

what does hydrophilic mean

Answer 4

attracting water

Question 5

what does hydrophobic mean

Answer 5

repels water

Question 6

how do lipid soluble molecules move through the bilayer?

Answer 6

move through the phospholipid portion,

Question 7

what si the function of the phospholipid bilayer?

Answer 7

• allow lipid soluble molecules to move through
• prevent water soluble molecules entering or leaving the cell - preventing osmotic lysis
  -make the membrane flexible and self sealing

Question 8

what do proteins do in the bilayer

Answer 8

act as receptor cells or cell recognition and in conjunction with glycolipids

Question 9

what is a phospholipid

Answer 9

lipids with a phosphate group

Question 10

are phosphate positively or negatively charged

Answer 10

negatively

Question 11

what is an extrinsic protein

Answer 11

attach only to the outside of the phospholipid

Question 12

what is an intrinsic protein

Answer 12

spans across the whole bilayer

Question 13

what is a glycoprotein

Answer 13

proteins with short carbohydrate chains attached

Question 14

what is a glycolipid

Answer 14

lipid with a short carbohydrate chain attached but is also involved in cell recognition and receptors

Question 15

what is the function of cholesterol

Answer 15

will reduce membrane fluidity!!!!!!! and fits in-between the phospholipid

Question 16

protein channels - what do they do

Answer 16

allows smaller molecules to pass through the bilayer

Question 17

why do some molecules not diffuse easily across the bilayer

Answer 17

• not soluble in lipids and therefore cannot pass through the bilayer
• too large to pass through the protein channels
• of the same charge as the protein even of they are small enough they will be repelled
• if they are polar molecules so will therefore have difficulty passing through the non-polar hydrophobic tails

Question 18

describe the fluid mosaic model

Answer 18

• fluid - phospholipid molecules can move relative to one another- this gives the membrane a flexible structure taht is constantly changing
• mosaic - the protein in the bilayer vary in shape, size and pattern

Question 19

how does cholesterol reduce membrane fluidity??

Answer 19

pulls together fatty acid tails of the phospholipid molecules and therefore restricting movement but without making the whole molecule rigid

Question 20

what are the general function of MEMBRANES

Answer 20

entry and exit of materials synthesised by mitochondria or chloroplasts or the other way round

• separate organelles from cytoplasm so that specific metabolic processes can atke place
• isolating the rest of the cell from damaging lysozymes
• provide surfaces on which reactions can occur e.g. protein synthesis using ribosomes on the RER.