Cell membrane Pratical

Question 1

describe the cell membrane

Answer 1

• Phospholipid bilayer made out of hydrophilic heads and hydrophobic tails
• Have gylcolipids in the phospholipid bilayer
• Have channel proteins
• Carrier proteins
• Polar head groups

Question 2

what is the cell membrane permeable towards

Answer 2

• Permeable to gases
• Permeable to small uncharged polar molecules
• These molecules cross cellular membranes by passive diffusion unaided by transport proteins
• Slightly permeable to water and urea

Question 3

what is the cell membrane impermeable too

Answer 3

impermeable to ions and large uncharged polar molecules

Question 4

how do cell membranes allow the passage of polar molecules

Answer 4

• A carrier protein alternatives between two conformations so that the solute binding site is sequentially accessible on one side of the bilayer and then on the other side
• A channel protein forms a water filled pore across the bilayer through which specific solutes can diffuse

Question 5

describe membrane proteins

Answer 5

• Single and multiple pass alpha-helix, intergral membrane protiens these can also be lipid anchored
• Rolled up beta sheet barrels
• Anchored by an amphiphilic alpha helix
• Via lipid anchors
• Association via non-covalent interaction with a bona fide membrane protein

Question 6

what did the results of the experiment show

Answer 6

• Showed that propanol-1 causes the largest increase in absorbance and therefore the largest distripution to the membrane
• The longer the molecules the greater the extent of membrane damage
• This is because the long the alkyl chain becomes the more hydrophobic (less polar and less hydrophilic) the molecules becomes therefore the more likely it is to interact with non-polar lipophilic molecules such as membrane lipids

Question 7

what are factors that affect the lipid bilayer

Answer 7

• An increase in alkyl chain and therefor either size of the alcohol will also cause a greater disruption in the packing of membrane lipid bilayer
• Futhermone, increasing the concentration will increase the amount of alcohol that associates with the lipids in the membrane and ultimately cause enough disruption that the cell contents leak out

Question 8

describe the blood alcohol content

Answer 8

• Blood alcohol content can be expressed as a percentage of alcohol in the blood/body fluids
• The BAC limit to drive legally within the UK is 0.08%

Question 9

describe lipid theory

Answer 9

• At high concentration the alcohol disrupts the lipid bilayer leading to the disruption of membrane fluidity this is lipid theory

Question 10

describe protein theory

Answer 10

• At lower concentrations ethanol can interact specifically with membrane bound protiens, e.g. receptors especially within the CNS (protein theory) causing changes in cell signalling

Question 11

what is the worse effect of alcohol on the phospholipid bilayer, lipid theory or protein theory

Answer 11

• Most evidence suggests that the later interaction(protein theory0 is more relevant to the effects of ethanol on the body during alcohol intoxication