Enzymes.

Activation energy:

The minimum amount of energy particles must have to be able to react.

Enzymes work by lowering this activation energy.

• The lock and key model is one model for enzyme action.
• Enzyme (rigid lock) binds with substrate (complementary key)
• However, active site of an enzyme has been observed to change shape when in the presence of a non-competitive inhibitor.

• This model proposes that enzymes are not rigid 'lock' structures.
• They are able to slightly change the shape to accomodate the substrate.

• Temperature affects enzymes. All enzymes have an optimum temperature: At lower temperatures, enzyme works slower. At highter temperatures, enzyme denatures.

Denaturation.

• Temperature provides the molecule in the enzyme with more kinetic energy. This causes the molecules to vibrate, causing the bonds to break.

Enzymes in the body:

• Enzymes optimum temperature is 40°C.
• A highter temoerature would increase metabolism, however, would require more food.
• Other proteins in the body may denature.
• It allows buffer during illness.

• Effects of pH differ from temperature.
• Enzymes have an optimum pH: If pH is lower, enzymes denature. If pH is higher, enzymes denature.

pH on enzymes:

• Changes can cause individual charges on amino acids in the active site to change, so substrate cannot bind.
• Also can affect ionic bonding between charged COOH and NH² groups, damaging tertiary structure.