Enzyme Structure and Function

Enzyme Structure and Function

• Enzymes have a "rigid" active site, which must fit with the substrate (key) to facilitate product formation.
• The shape of the active site determines the shape of the substrate it can bind to.
• If the substrate has a different shape, it won't bind to the enzyme, and no product formation occurs.
• The active site remains unchanged after product formation.

Enzyme Inhibition

• Inhibitors bind to the allosteric site, modifying the active site and preventing product formation.
• The inhibitor changes the conformation of the active site, making it incorrect for the substrate.

Enzyme Theories

Lock and Key Theory (Emil Fisher's)

• Enzymes have a "rigid" active site that matches the shape of the substrate.
• The active site and allosteric site are significant for enzyme structure.

Induced Fit Theory (Kochland's)

• Enzymes have a "flexible" active site that changes shape to fit the substrate.
• The active site's shape is not the same as the substrate's shape, but it can adapt to fit.
• The enzyme's shape remains the same after product formation.

Enzyme Kinetics

• Enzyme kinetics describes how enzymes work in the presence of substrate and product formation.
• Enzymes lower the activation energy required for a reaction.
• Activation energy is the excess energy required to raise all molecules in one mole of a compound to the transition state.
• The transition state is where the molecule is equally likely to participate in product formation or remain as an unreacted molecule.

Enzyme-Substrate Complex

• The enzyme-substrate (ES) complex shows the physical binding of a substrate to the active site of an enzyme.
• The ES complex has a high energy that decreases to a low energy after product formation.

Chemical Reaction

• Chemical reactions involve a downhill movement of energy from high-energy reactants to low-energy products.
• Enzymes reduce the free energy needed to activate the reaction.
• The substrate must surpass the energy barrier to react with the enzyme and form products.

Types of Enzyme Specificity

Absolute Specificity

• An enzyme combines with only one substrate and catalyzes only one reaction.

Group Specificity

• Enzymes combine with all substrates in a chemical group, catalyzing a specific reaction.