Enzymes
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Enzymes

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VCE Biology

VCE Biology

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    Enzymes Enzymes Presentation Transcript

    • Chapter 3 Nature of Biochemical Processes
    • Key Terms
      • Metabolism – 1000’s of chemical reactions in organisms. Gives off heat depending on metabolic rate
      • Catabolic – breakdown of complex molecules into simpler molecules. Energy is released (exergonic).
      • Anabolic – atoms and molecules are joined to build complex molecules. Energy is required (endergonic)
    • Key terms (continued)
      • Exergonic reactions release energy and involve the breakdown of complex molecules (catabolic) egs. Oxidation and respiration
      • Endergonic reactions consume energy and involve building complex molecules (anabolic) egs. Reduction and photosynthesis
      • Reactions are controlled/regulated by biochemical pathways (enzymes)
      • Exergonic and endergonic reactions happen simultaneously. ATP carries energy to necessary locations in the cell.
    • Antioxidant
      • Antioxidants prevent tissue damage by preventing oxidative reactions (energy releasing) as they can damage the cells
      • (see page 61 of Nature of Biology)
    • ATP
      • Mitochondria produce ATP (adenosine triphosphate). Energy is released when ATP is hydrolysed (split by adding H 2 O). ADP and a phosphate molecule are the products.
    •  
    • Enzymes
      • Biological catalysts . A catalyst speeds up (catalyses) a chemical reaction that would otherwise take place at a much slower rate.
      • Enzymes:
      • - are proteins (usually folded to create a specific active site )
    •  
      • Enzymes:
      • - are substrate specific
      • - can be used over and over again
      • - are needed in small amounts (they are not reactants or products)
      • - reduce energy needed for a reaction to happen ( activation energy )
      • - can catalyse a reaction in either direction
      • - do not increase the final amount of product
    • Enzymes
      • Enzymes may require other cofactors to work
      • eg. Metallic ions like Zinc
      • Organic molecules that act as cofactors are called coenzymes
      • eg. vitamins
    • Enzymes and their substrates
      • Enzymes act only on specific substrates – the active site binds to a part of the substrate.
      • Lock and key
      • Induced fit (see pg 66, Fig 3.10)
      • Poisons block active sites and stop enzyme action
    • Induced fit
    • Lock and key
    • Activation energy and enzymes
      • Chemical reactions involve the breaking and remaking of chemical bonds.
      • Energy needed to get reaction started (called activation energy)
      • Enzymes act by reducing the activation energy (see Fig. 3.8, p65)
    • Activation energy
    • Factors affecting enzyme activity
      • pH
      • Change in pH can change the shape of the enzyme.
      • Biological fluids normally in the range 6–8
      • Optimal pH for each enzyme
      • eg. Pepsin – stomach (2)
      • Trypsin – small intestine (8)
    • Factors affecting enzyme activity
      • Temperature
      • Optimal temperature approx. 37
      • High temperature leads to denaturation
      • Low temperature is preserving; will reactivate at optimal temperature
    • Factors affecting enzyme activity
      • Enzyme concentration
      • Only small amounts required
      • Increased enzyme conc. leads to increased production rate
      • Substrate concentration
      • Increase in substrate will increase production rate only until all active sites are in use
    • Enzyme inhibition
      • Other molecules compete with substrate for the active site and may bind permanently.
      • Interferes with enzyme function and may be lethal eg. cyanide
    • Enzyme inhibition
      • Competitive inhibitor – competes for active site an binds permanently. Eg. O 2 on rubisco enzyme in C3 plants instead of CO 2
      • Non-competitive inhibitor – doesn’t bind with the active site permanently.