ENZYMES

The Induced Fit model states the active site is not rigid; substrate binding induces a conformational change that properly positions catalytic groups for optimized catalysis.

At high substrate concentrations, all enzyme active sites are occupied. The reaction velocity reaches a maximum (Vmax), and further substrate addition cannot increase the rate.

Km is a measure of an enzyme's affinity for its substrate, defined as the substrate concentration at which the reaction rate is one-half of the maximum velocity (Vmax).

Unlike inorganic catalysts, enzymes are highly specific and their activity is finely regulated by cellular mechanisms like allosteric control.

By lowering the activation energy, enzymes allow a much larger proportion of substrate molecules to reach the transition state at a given temperature, increasing the reaction rate.

The protein portion alone is the inactive apoenzyme, which requires a non-protein cofactor to form the complete, active holoenzyme.

Enzyme specificity arises from the unique 3D structure of the active site, which contains amino acid R-groups positioned to form interactions only with a specific substrate.

The induced fit model is exemplified by conformational changes in hexokinase upon glucose binding, which correctly orient ATP for catalysis.

Enzymes are biological catalysts that accelerate reactions by decreasing the activation energy. They do not provide energy, alter the equilibrium constant, or change the free energy change (ΔG) of the overall reaction.

The tertiary structure of an enzyme, which dictates the shape of the active site, is stabilized by hydrogen bonds, ionic interactions, hydrophobic interactions, van der Waals forces, and covalent disulfide bonds.

A prosthetic group is a non-protein unit that is covalently or very tightly bound to an apoenzyme, making it a permanent part of the functional holoenzyme.

The active site is a specific, flexible 3D pocket formed by a few amino acids that binds the substrate and catalyzes its conversion to product via weak interactions.

Enzymes lower activation energy by providing an alternative reaction pathway where specific R-groups orient and stress substrates, stabilizing the transition state.