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HSC Biology

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Lesson 2, Topic 2
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Cell Requirements

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Organic Compounds

  • The building blocks of all living things.
  • Contain Carbon (C), Hydrogen (H) and Oxygen (O) molecules.

Four types of organic compounds:

  • Carbohydrates
    • Used for quick energy
    • Starch (stored in plant cells)
  • Lipids
    • Contain many H and C molecules with a few O
    • Energy storage
    • Structural component of membranes
    • Essential parts of hormones
  • Amino acids
    • Contain H, O, N and P molecules
    • Two types of Nucleic Acids:
      • DNA (deoxyribonucleic acid)
        • Stores information that controls cells.
        • Contains 4 bases: adenine, guanine, cytosine and thymine.
      • RNA (ribonucleic acid)
        • Large amounts in cytoplasm
        • Contains 4 bases: adenine, guanine, cytosine and uracil.

Inorganic Compounds

Five types of inorganic compounds:

  • Water (H_{2}O)
    • Constitutes 70-90% of most organisms
    • Important solvent and transport medium
    • Chemical reactions in cells occur in water-based fluids
    • Some reactions include water (photosynthesis)
  • Oxygen (O_{2})
    • Important for efficient energy supply, achieved by the process of cellular respiration in almost all organisms.
    • Taken in as a gas by terrestrial organisms and in solution by aquatic organisms.
  • Carbon Dioxide (CO_{2})
    • Fundamental source of vital carbon atoms for organic molecules, usually starting carbon fixation by photosynthesis in autotrophs.
    • Taken into plant leaves as a gas, converted to sugars and eventually returns to the atmosphere in the carbon cycle.
  • Nitrogen (N)
    • Makes up amino acids, which make up proteins.
    • Plants absorb from soil.
    • Absorbed by bacteria to make nitrates.
  • Minerals
    • Make enzymes which are needed for the structure and function of biological systems.
    • Calcium is needed for bones and teeth.
    • Sodium and potassium are important for the nervous system.
    • Magnesium is important for muscular function.
    • Iron is required for haemoglobin.