C5: Biological Membrane

Question 1

describe the difference between active & passive transport and examples

Answer 1

active

• needs energy in the form of Atp
• used when diffusion isnt possible or fast enough (wrong concentration gradient)

ex. active transport, bulk transport

passive

• doesn’t need energy
• when molecules need to be transported from a HIGH to LOW concentration

ex. diffusion, osmosis, facilitated diffusion

Question 2

the role of the plasma (cell) membrane

Answer 2

• site of chemical reactions
  hold proteins/enzymes involved in reactions in place
• acts as barrier
  partially permeable membrane = allows small/non-polar/lipid soluble substances to diffuse across bilayer
• compartmentalisation
  provides specific consistimos for certain reactions to happen

Question 3

properties of glycolipids and glycoproteins in the plasma membrane

Answer 3

glycoprotiens = attached to a protein

glycolipids = attatched to a phospholipid

• both have carbohydrate chains that act as receptors/antigens
• receptors are for signalling
• antigens are got cell recognition

Question 4

property & function of cholesterol in the plasma membrane

Answer 4

cholesterol: hydrophobic carbon, hydrophilic head

- regulates fluidity and makes the membrane more or less rigid

Question 5

explain how temperature rise affects the membrane structure

Answer 5

1. the H bonds between the phospholipids tails are close together to keep stable + stop things passing through
   2) temperature rises = KE increases
   3) gain in EK moves them further apart + breaks the H bonds between them. causes membrane to lose its structure = becomes more permeable
   4) TOO HIGH TEMP denatures the proteins in membrane

Question 6

explain how solvents affect the membrane structure

Answer 6

1) non polar/hydrophobic solvents can get through the membrane and sit between tails.
2) this breaks apart the H bond and disrupts the phospholipid bilayer
3) makes it more permeable + polar stuff can get through

Question 7

difference between an extrinsic and an intrinsic protein

Answer 7

intrinsic = a protein embedded WITHIN the membrane

extrinsic = a protein that exists ON the surface

Question 8

whys the phospholipid bilayer/plasma membrane described as being FLUID and MOSAIC

Answer 8

fluid = components aren’t fixed in place and can move freely along the membrane

mosaic = the different shapes + sizes components can all fit together

Question 9

phospholipid is made of

Answer 9

• hydrophilic phosphate head
• 1 glycerol backbone
• 2 fatty acids, make up hydrophobic tail