BIOLOGY PAPER 1

• Cells divide when:

  • an organism grows
  • an organism becomes damaged and needs to produce new cells
• MITOSIS HERE

  
• to calculate sa;v ratio -calculate area of each surface and add them together - calculate volume -show as simplified ratio
• an exchange surface is a specialized are of an organism where substances are efficiently transferred between organism and environment
• plants are adapted for gas exchange by -stomata let gases inn and out - air spaces inside leave let gases in and out of cells
• the effect of different concentrations of salt solutions on plant tissue can be investigated by comparing the change in mass of potato cylinders after leaving them in a salt solution for the same time
• microscopy practical

  • place slide on stage
  • select lowest power objective lens (4x)
  • turn coarse dial slowly and look from side
  • look through the eye piece
  • turn coarse dial slowly, this increases the distance between objective lens and slide until cells focus
  • turn fine dial to focus cells
  • image/real= magnification
  • adjust fine dial to bring cells into focus
  • remember to label cell structures in pencil and add magnification in mm with ruler
• CULTURING MICROORGANISMS PRACTICAL pre steps

  • pass inoculating loop through flame
  • sterilize petri dish to prevent contamination
  • attach lid with adhesive tape so it doesn't fall off and unwanted microorganisms enter
  • place upside down to prevent moisture dripping down and disturbing colonies
  • incubate at 25 to prevent harmful bacterial growth
• CULTURING MICROORGANISMS PRACTICAL

  • clean bench with disinfectant to kill unwanted microorganisms
  • sterilize inoculating loop through flame
  • open agar plate near flame this will kill any unwanted bacteria in the air
  • using loop, spread bacteria over plate
  • place sterile filter paper containing antispetic on agar plate
  • incubate at 25 for 48 hours
• to calculate zone of inhibition use pie x radius ^2
• osmosis practical with potato

  • peel potato
  • cork borer to produce 3 cylinders of equal diameter
  • scalpel to trim them to same length (3cm)
  • measure length and mass with ruler and balance
  • place potato in test tube, first test tube
• using a light microscope to look at a prepared slide
• using a light microscope to look at a prepared slide

  • put slide on stage and attach with clips
  • select lowest power lens
  • use coarse adjustment knob to roughly focus slide
  • use fine adjustment knob to clearly focus slide
  • switch to higher power lens to increase magnification and refocus with the fine adjustment knob
• the function and structure of red blood cells
• red blood cells biconcave shape increases suface area therefore the oxygen they transport
• when blood enters the heart, through the vena cava, it goes to the right atrium then the right ventricle then out the pulmonary vein to the lungs
• blood comes into the heart from the lungs through the pulmonary artery then goes to left atrium to the left ventricle then out the aorta to the body
• the left side has thicker walls as it transports high pressure blood to the whole body
• arterys carry blood away from the heart at a high pressure so they have thick walls and a small lumen to withstand the pressure
• veins carry blood back to the heart as deoxygenated blood with low pressure they have thin walls and a large lumen, and valves to prevent backflow of deoxygenated blood
• capillaries have one cell thick walls to have fast diffusion of blood and cells
• non communicable diseases

  • diabetes-poor diet and obesity
  • heart disease-poor diet and lack of exercise
  • liver diseases-alcohol
• cancer is an autoimmune disease where damaged cells divide uncontrollably and form tumors . carcinogens increase risk of developing cancer.
• benign cancer will not spread but malignant cancer will and it invade other parts of the body
• phloem transport by active transport
• rate of transpiration can be increased by

  • temp
• the meristem of a plamnt is where new cells are made
• • waxy cuticle - waterproof layer to stop water evaporating from leaf
  • palisade mesophyll- cells with lots of chloroplasts where photosynthesis ocours
  • spongey mesophyll contains air spaces where gas is exchanged maximises rate of diffusion
• guard cells control size of stomata
• animal aerobic resp = glucose to lactic acid (broken down by liver using oxygen)
• lymphocytes produces antibodies that bind to the viruses antigen, stopping the infection of any more cells
• phagocytes ingest and destroy the virus
• iv is what you change

  dv is what you measure

  control v is what must be kept constant
• microscopy use onion skin cell with a drop of iodine to make it visible
• to determine optimum temp for enzyme use water bath

  to determine opt ph use buffer solution
• effects of temp on amalayse
• effect of ph on enzyme activity

  • drop of iodine in spotting tile
  • bunson burner on heat proof mat with tripod and gauze over
  • heat water until 35
  • use a syringe to add 1cm of amlase solution and 1cm of ph5 buffer solution to a boiling tube
• effect of ph on enzyme activity 2

  • use differnet syringe to add 5cm of starch solution to the boiling tube
• effect of ph on enzyme activity 3

  • immediately mix contents and start a clock
  • use continuous sampling to record how long it takes the amylase to break down all of the starch
  • use pippette to drop sample from boiling tube every 30 seconds and drop it in a well
• effect of ph on enzyme activity 4

  • when the iodine remainsbrowny orange startch is no longer present
  • repeat experiemtn with range of diff ph buffer solutions to see how ph effects time taken for startch to be broken down