BIOLOGY 4.3

BIOLOGY 4.3

1. PLANTS NEED MINERALS

   • NITRATES
     • Contain nitrogen for making amino acids
     • Needed for proteins for cell growth
     • Without: poor growth & yellow leaves
   • PHOSPHATES
     • Contain phosphorus for making DNA and cell membranes
     • Needed for respiration and growth
     • Without: poor root growth & discoloured leaves
   • POTASSIUM
     • Potassium compounds to help enzymes in respiration and photosynthesis
     • Without: poor flower/fruit growth & discoloured leaves
   • MAGNESIUM
     • Magnesium compounds for photosynthesis
     • Needed to make chlorophyll
     • Without: yellow leaves
   • ACTIVE TRANSPORT
     • Root hairs give the plant a big surface area for absorbing minerals
     • Concentration of minerals in soil is low - higher in root hair cell
     • Uses energy from respiration to help plant pull minerals into the root hair against the concentration gradient (from low to high conc)

2. DECAY

   • Things decay because of microorganisms/decomposers
   • The rate of decay depends on:
     • Temp
       • Hotter = faster - respiration in microorganisms is sped up
     • Water
       • Moist = fast decay
     • Oxygen/air
       • More oxygen = faster - microorganisms can respire aerobically
   • DETRIVORES
     • Feed on dead and decaying material
     • e.g. earthworms, maggots, woodlice
     • Break material up into small bits
       • This gives a bigger surface area to work on and speeds up decay
   • SAPROPHYTES
     • Feed on decaying material by extracellular digestion
       • i.e. feed by secreting digestive enzymes on to the material outside of their cells
         • The enzymes break down the materials into smaller bits which can be absorbed by the saprophyte
     • Many saprophytes are fungi
   • PRESERVING FOOD
     • Canning
       • Keeps decomposers out
     • Cooling
       • Slows decomposers' reproduction rate
     • Freezing
       • Decomposers can't reproduce
     • Drying
       • Decomposers need water for cell reactions
     • Pickling
       • Acid kills decomposers
     • Adding sugar/salt
       • High sugar conc = loss of water by osmosis - decomposers can't work properly