biology

• Movement of ions into guard cells by active transport

  1. Move against the concentration gradient

  2. Proteins (in membrane)

  3. Using energy from respiration
• Protein molecules moving ions across a membrane

  1. Protein uses ATP (from respiration)

  2. Protein interacts with ions

  3. Protein changes shape

  4. Ions move through the protein against concentration gradient
• Osmosis


  A form of diffusion
• Trophic level A is smaller than trophic level B in the pyramid of biomass


  Energy is lost from the food chain as it is transferred from one trophic level to the next
• Only 10% energy is transferred between trophic levels
• Energy is lost as heat, in respiration, and movement
• Not all organisms in one trophic level are eaten, and not all parts of the organisms are eaten
• Not all nutrients in the organisms are eaten, digested or absorbed
• Some energy is lost in excretion, urine and faeces
• Some energy is transferred to decomposers
• Pyramid of biomass


  Indicates how much food is available/left, and is an indicator of the energy available
• Penicillin is produced by a fungus
• Bacteria becoming resistant to antibiotics

  1. Mutation leads to variation in ability to survive antibiotic treatment

  2. Bacteria with resistance survive and breed, passing on resistant allele
• How humans can reduce antibiotic resistance

  • More responsible use of antibiotics
  • Improved detection/screening to avoid spread
  • Improved cleanliness
  • Isolating infected patients
  • Development of new antibiotics/treatment
• Viruses are not alive and do not have a cell wall or nucleus
• Bacteria useful in biotechnology

  • Small, take up little space
  • Reproduce rapidly, easy to grow
  • Contain plasmids
  • Can be genetically modified
  • No ethical concerns
  • Same genetic code as other organisms
  • Can make complex molecules
• Using bacteria in genetic engineering to produce human proteins

  1. Identify/isolate human DNA/gene

  2. Cut DNA/gene/plasmid using restriction enzymes

  3. Form complementary/sticky ends

  4. Cut plasmid with same restriction enzymes

  5. Form recombinant DNA/plasmid

  6. Use ligase to join plasmid and gene

  7. Insert plasmids into bacteria

  8. Bacteria replicate/reproduce/multiply
• Steam is used to clean fermenters to kill pathogens and prevent contamination without chemically contaminating the product
• Advantages of genetically modifying crops

  • Disease resistance
  • Larger/faster yield
  • Drought resistance
  • Salt resistance
  • Frost resistance
  • Nutritional enrichment
  • Pest/insect resistance
  • Herbicide resistance
  • Vaccine production
  • More desirable product/increased income
  • Growth modification
• Yeast used in bread-making

  1. Respiration/fermentation produces carbon dioxide

  2. Carbon dioxide causes dough/bread to rise

  3. Enzymes (e.g. amylase) digest starch
• Using Penicillium to make penicillin


  1. Grow Penicillium in fermenters

  2. Provide aerobic conditions, sugars, nitrogen source, nutrients

  3. Purify/filter product

  4. Batch culture, sterile conditions
• Antibiotics can treat bacterial infections but not viral infections because bacteria are made of cells while viruses are not alive and do not have a cell wall
• Ways to sterilise a fermenter

  • Steam
  • Autoclave/high temperature and pressure
  • UV/gamma/X-ray radiation
  • Bleach
• Functions of fermenter parts

  • Stirrer: keeps microorganisms suspended, enables access to nutrients, maintains even temperature, creates uniform mixture
  • Water-filled jacket: reduces/maintains constant temperature
  • Probes: monitor temperature, pH, gas concentration, pressure, nutrients
  • Outlet: allows collection of liquid containing product after fermentation
• Processing liquid containing penicillin after collection from fermenter


  Separated/extracted/filtered/centrifuged/evaporated/purified/crystallised/precipitated/dried, impurities removed
• Air and nutrients added to fermenter must be sterile to prevent contamination
• Loss of water through leaf transpiration

  1. Xylem supplies water from soil

  2. Air spaces in leaf

  3. Large internal surface area of leaf

  4. Water evaporates from mesophyll cell surfaces

  5. Guard cells open/close stomata

  6. Water vapour diffuses out through stomata
• Features of xylem vessels

  • Thick/strong cell walls to withstand tension/pressure
  • Lignin in walls makes them impermeable
  • Wide to transport large volumes of water
  • No cell contents, like empty pipes
  • No cross walls or end walls, allowing continuous flow
• Water movement from soil to xylem in root

  1. Water enters root hair cells by osmosis

  2. Moves through root cortex to xylem
• Mechanism of water movement in xylem

  1. Evaporation from mesophyll cell walls

  2. Diffusion of water vapour through stomata

  3. Reduced pressure/water potential at top of plant

  4. Cohesion of water molecules

  5. Transpiration pull
• Increase in temperature


  Increases rate of transpiration
• Reduced water vapour concentration in air


  Increases movement of water through crop plants
• Stomata


  Allow gas exchange and diffusion for photosynthesis, respiration, and transpiration
• Phloem


  Transports food (source) to areas of growth and storage (sink)
• Water movement from root to stomata

  1. Moves from root cells into xylem

  2. Cohesion/adhesion pulls water up xylem

  3. Mass flow of water (transpiration stream)

  4. Water moves into leaf by osmosis

  5. Evaporation from mesophyll cells lowers water potential
• Cones


  Detect colour, less sensitive in low light
• Rods


  Work in low light but cannot detect colour
• Liver's response to increased insulin

  1. Stimulates enzyme production

  2. Converts glucose to glycogen for storage

  3. Increases uptake/absorption/respiration of glucose
• Mechanism increasing blood flow through skin

  1. Sensory neurons/receptors detect stimulus

  2. Brain/hypothalamus as control centre sends impulses to motor/effector neurons

  3. Muscles in shunt vessels contract/arterioles relax to dilate arterioles
• The eye is a sense organ that responds to light