key things that come up in paper 1

• for cell cycle the percentage of cells in that stage = the time spent in that stage
• describe how hiv is replicated inside of helper t cells ( 4 marks)

  • rna is converted into dna using reverse transcriptase
  • the dna is inserted into nucleus of helper t cell
  • the dna is then transcribed into mrna
  • this mrna is then translated into hiv proteins to make viral particles
• cells mitosis practical question:

  • why to use the first 5mm from root tip - this is where mitosis occurs
  • why to press down on cover slip firmly - to create a single layer of cells so that light can pass through
  • why to add acid - to break down links between cell walls
• suggest and explain the function of atp hydrolase in absorbing amino acids:

  • hydrolyses atp into adp + pi - releasing energy
  • this energy actively transports sodium out of epithelial cell and into blood
  • this creates a concentration gradient
  • sodium ions are co transported into epithelial cells with amino acids
• how to answer question about comptetitive inhibitor (3 marks)

  • substance similar in shape to substrate
  • so substance can bind to enzymes active site instead of the substrate
  • this prevents e-s complexes from being formed
• a student wanted to determine whether sucrose was a reducing or non reducing sugar . describe a test to show this

  • add benedicts reagent and heat
  • benedicts remains blue as its a non reding sugar
  • then add acid and boil - to break glycocidic bonds
  • then add alkali to neutralise
  • add benedicts reagent and heat
  • brick red colour formed
• describe the test for a lipid

  add ethanol and shake

  then add distilled water

  white emulsion forms
• explain how the movement of na + out the cell allows for the absorption of glucose into cell

  lower concentration of sodium in cell so creates a concentration gradient

  so sodium moves in down its concentration gradient via facilitated diffusion bringing glucose with it
• describe how amino acids join to form A polypeptie

  • nh2 group on one amino acid bonds to carboxyll group on another amino acid
  • forming a peptide bond
• describe the mechanism by which the arteriole regulates blood flow to capilllaries


  smooth muscle within arteriole contracts

  this constricts the lumen of the arteriole
• describe the function of the coronary arteries

  carries oxygen to heart
• explain how heart contributes to tissue fluid formation

  contraction of ventricles causes high hydrostatic pressure

  this forces out water and dissolved substances