biology paper 1

• plants with magnesium deficiency will have yellow leaves and stunted growth because of a lack of chlorophyll so less light absorbed so less photosynthesis so the plant makes less glucose so less proteins can be made for growth so growth is stunted
• making monoclonal antibodies:

  inject the protein into a mouse and combine with a tumour cell to make a hybridoma

  find a hybridoma which makes a monoclonal antibody specific to the protein

  clone the hybrid to produce many identical antibodies
• Differences between red blood cells and plant cells

  • Red blood cell has no nucleus or plant cell has a nucleus
  • Red blood cell has no cell wall or plant cell has a cell wall
  • Red blood cell is a biconcave disc or there are many different shapes of plant cell
  • Red blood cell contains haemoglobin or plant cells do not contain haemoglobin
  • Red blood cells do not contain chlorophyll or plant cells (may) contain chlorophyll
  • Red blood cell has no chloroplasts or plant cell has chloroplasts
  • Red blood cell has no (permanent) vacuole or plant cell has (permanent) vacuole
  • Red blood cells are (much) smaller than plant cells
• Similarities between red blood cells and plant cells

  • Both have cytoplasm
  • Both have cell membrane
  • Both have pigments (although they are different)
• Structural differences between xylem and phloem

  • Xylem is made of dead cells
  • Phloem is made of living cells
  • Phloem cells have pores in their end walls
  • Xylem cells do not have pores in their end walls
  • Xylem is hollow or xylem does not contain cytoplasm
  • Phloem contains cytoplasm
  • Xylem contains lignin
  • Phloem does not (contain lignin)
• • Both xylem and phloem are made of cells
  • Both are tubular
• Functional differences between xylem and phloem

  • Xylem transports water / mineral ions
  • Phloem transports (dissolved) sugars
  • Xylem is involved in transpiration
  • Phloem is involved in translocation
  • Xylem transports unidirectionally
  • Phloem transports bidirectionally
• Reasons for tiredness

  • Fewer red blood cells
  • Less haemoglobin
  • Less oxygen transported around the body
  • Less (aerobic) respiration can take place
  • More anaerobic respiration takes place
  • Less energy released for metabolic processes
  • Less energy released so organs cannot function as well
  • Lactic acid produced (during anaerobic respiration) causes muscle fatigue
• Reasons for frequent infections


  • Fewer white blood cells/phagocytes/lymphocytes
  • Fewer antibodies produced or less phagocytosis
  • Fewer pathogens / bacteria/viruses killed
• Reasons for bleeding


  • Fewer platelets
  • Blood does not clot as easily
• the main difference between prokaryotic and eukaryotic cells is that prokaryotes do not contain a nucleus whereas eukaryotes do
• antibiotics kill bacteria by disrupting their cell membranes or interfering with enzymes needed for DNA replication
• Clinical trials for mAbs treatment

  1. First given to healthy volunteers at a very low dose to test it is safe

  2. Then given to some patients with the disease to check for optimum efficacy and to check for side effects

  3. In a double blind trial where neither the patient or doctor know who has the mAbs and who has the placebo

  4. Large trial over a long duration

  5. People of the same gender
• effects of blocked coronary artery:

  less blood

  less oxygen and glucose flows to the heart muscle

  so heart anaerobically respires

  so less energy released and lactic acid produced

  so heart can’t contract as efficiently so less blood pumped around the body

  less aerobic respiration in body cells anaerobic respiration causes lactic acid so muscles become fatigued person gets tired and breathless as they need to breathe in more oxygen
• Function of nerve cells


  To carry electrical signals from one part of the body to another
• Nerve cells


  • They are long (to cover more distance)
  • They have branched connections at their ends to connect to other nerve cells and form a network throughout the body
• How the pregnancy test strip works to show a positive result

  1. Urine passes through reaction zone

  2. Mobile antibodies bind HCG

  3. Urine continues up the stick

  4. HCG binds to immobile antibody in reaction zone creating blue line

  5. Antibodies not bound to HCG move up to control window and bind to immobile antibodies there creating another blue line
• Microscopy

  1. Peel a one-cell layer of skin from an onion

  2. Place on a microscope slide

  3. Add a drop of iodine to stain the cells

  4. Place a cover slip on top

  5. Place on the microscope stage

  6. Turn on the light or position mirror so light reflects through the condenser to the slide

  7. Use the lowest magnification objective lens

  8. Use the coarse and fine focus knobs to focus

  9. Increase magnification and refocus if needed
• osmosis rp

  • independent variable is conc of sugar solution
  • dependent variable is %change in mass
  • cut equal size cylinders of potato
  • remove skin
  • remove excess water from surface and weigh
  • place each into a test tube with different concentrations of sugar solution
  • leave for a day
  • water moves in or out by osmosis
  • remove potatoes and dab off water with paper towel
  • reweigh
  • calculate %change in mass
• enzymes rp

  • independent: temp or pH
  • dependent: time for substrate to be broken down
  • measure out enzyme and substrate
  • place separately in a water bath with buffer solution if testing pH
  • prepare spotting tile with iodine
  • mix reactants and start timer
  • every 10 seconds remove a drop of mixture and put in a dimple of iodine
  • if colour changes starch is present
  • once all starch broken down colour won’t change
  • repeat at different temperatures or pH
  • draw line of best fit
  • optimum condition is between two lowest points
• food tests

  • grind food and add to distilled water
  • starch- add iodine, orange to black is present
  • sugars- benedict’s solution, heat in water bath to 65 degrees, if present blue to brick red
  • protein- biurets, blue to purple
  • lipids- cold ethanol then mix with water, goes cloudy
• photosynthesis rp

  • put pondweed in test tube
  • add sodium hydrogen carbonate
  • cut stem at angle
  • invert and put in beaker with no air at top
  • dark room
  • measure distance of lamp
  • wait 1 min to acclimatise
  • start stopwatch and count how many bubbles produced in a minute
  • change distance by 10cm each time and repeat
• aseptic technique

  • sterilise equipment
  • open petri dish towards flame
  • add drops of different bacteria onto agar
  • label dish with type of bacteria
  • seal lid with tape
  • incubate for a few days at 25 degrees
  • measure diameter of area with no bacteria