OCR 21st Century Science - Biology B456

B4 - The Processes of Life

  • Cell structure and function
    • Animal cell
      • Nucleus - contains DNA, the instructions for proteins
      • Cytoplasm - gel substance where proteins like enzymes are made, anaerobic respiration occurs here
      • Cell membrane - holds cell together and controls what goes in and out
      • Mitochondria - enzymes needed for aerobic respiration found here
    • Plant cells
      • Rigid cell wall - made of cellulose, supports and strengthens cell
      • Vacuole - contains cell sap, weak solution of sugar and salts
      • Chloroplasts - contain chlorophyll, place where photosynthesis occurs
    • Yeast - single cell microorganisms; nucles, cytoplasm, mitochondria, membrane, cell wall
    • Bacteria - no nucleus or mitochondria; cell membrane + wall, cytoplasm, circular DNA
  • Enzymes
    • Proteins that speed up chemical reactions
    • Have an 'active site' where the substrate (molecule changed) attaches to
    • At too high temp, bonds in the enzyme break, changing the shape of the active site
    • pH can also denature enzymes and prevent them from working
  • Aerobic respiration
    • A series of chemical reactions that release energy by breaking down food molecules
    • This energy is used for movement, active transport + synthesis of large molecules
    • Aerobic respiration needs oxygen, releases more energy than anaerobic
    • C6H12H6 + 6O2 --> 6C02 + 6H2O + energy released
  • Anaerobic respiration
    • Respiration without oxygen
    • Happens in humans during vigorous excercise; plants when roots become waterlogged
    • Glucose --> Lactic acid + energy released (animal cells/some bacteria)
    • Glucose --> Ethanol + carbon dioxide + energy released (plant cells/yeast)
    • Fermenting plant and animal waste gives biogas; yeast ferments hydrocarbons in flour making CO2, causing it to rise; yeast ferment sugar to form alcohol
    • Fermentation - microorganisms breaking down sugar as they respire anaerobically
  • Photosynthesis
    • Series of chemical reactions that use sunlight to produce food (glucose)
    • Chlorophyll absorbs sunlight and uses the energy to convert the CO2 and H20 into glucose
    • 6CO2 + 6H2O --> C6H12O6 + 6O2
    • Glucose is used for respiration; making amino acids when combined with nitrogen
  • Rate of photosynthesis
    • Light and CO2 increase rate up to a point, after which temp is limiting factor - enzymes denature at around 45 degrees
  • Investigating photosynthesis
    • Transect - measure between two fixed points, move along and colect data you want
    • Light meter - measures levels of light
    • Quadrat - 10x10 grid, used for percentage cover
    • ID Key - series of questions narrowing down options until identification
  • Diffusion, osmosis and active transport
    • Diffusion - the passive overall movement of particles from an area of high concentration to an area of low concentration
    • Osmosis - the overall movement of water particles across a partially permeable membrane from an area of low concentration to and area of high concentration
    • Active transport - overall movement of chemicals across a cell membrane from a region of low to high concentration using energy released by respiration

B5 - Growth and Development

  • DNA - making proteins
    • Structure
      • Double helix - two strands coiled…



Thanks for these notes!

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