- Biological catalysts
- Are protein molecules
- Offer alternative pathway with lower Activation Energy
- Are proteins that speed up chemical reactions, while remaining chemically unchanged at the end of the reaction, hence can be re-used, hence small volume required
- Without enzymes, metabolic processes will not proceed at a fast rate enough to sustain life (e.g. Digestion)
- Food molecules which are large and insoluble in water have to be digested with the help of enzymes into smaller, simpler molecules in order to pass through the plasma membrane for assimilation
- Digestive Enzymes:
- Amylase -> Speeds up the digestion of starch to maltose
- Maltase -> Speeds up digestion of maltose to glucose
- Protease -> Speeds up the digestion of proteins to amino acids
- Lipase -> Speeds up the digestion of fats to fatty acids and glycerol
- Enzymes are highly specific
- Lock and Key Hypothesis
- Enzyme binds to the substrate at active site
- Active site has specific 3D shape that is complementary to that of the substrate
- Creates Enzyme-Substrate Complex (E+SC)
- Enzyme remains unchanged!!!
- Enzyme + Substrate (E+S) -> Enzyme-Substrate Complex (ESC) -> Enzyme-Product Complex (EPC) -> Enzyme + Product (E+P)
- IMPORTANT: ENZYMES WILL TEST POSITIVE FOR BIURET’S TEST!!!!!!!
Denaturation §
- Active site is not present anymore
- weak bonds broken
- Unravels and becomes a disorganised tangle
- Irreversible change
Effects of Temperature §
- At low temps,
- Enzymes less active as they have low KE
- Chance of substrate and enzymes molecules colliding are low
- Rate of reaction is low
- As temps increase,
- Rate of enzyme-catalysed reactions increases
- Increase in kinetic energy of enzyme and substrate molecules increase chance of successful collision
- Usually reaction rate doubles for every 10°C increase
- At optimum temp,
- Beyond the optimum temperatures,
- Enzyme activity decreases as enzyme is denatured
- High temperature overcomes the bond within the enzyme and changes 3D shape
- At optimum pH,
- Active site most ideal for binding of substrate
- Highest frequency of collisions and effective collisions with substrate
- rate of ESC formation is the highest
- As pH moves away from optimum pH,
- Active site less ideal for binding of substrate
- lower frequency of collisions and effective collisions with substrate
- rate of ESC formation is lower
- Extreme pH denatures enzymes, resulting in no ESC forming
- Basically electrostatic repulsion of the substrate from the enzyme
- Caused by electrostatic change