Enzymes

Enzyme

A biological catalyst that speeds up chemical reactions by lowering activation energy.

Substrate

The specific molecule that an enzyme acts upon.

Active site

The region on the enzyme where the substrate binds.

Enzyme-substrate complex

A temporary complex formed when the enzyme binds its substrate.

Specificity (in enzymes)

Enzymes only act on one or a few specific substrates due to the shape of their active site.

Enzyme after reaction

It remains unchanged and can be reused.

Activation energy

The minimum energy required for a chemical reaction to start.

Effect of enzymes on activation energy

Enzymes lower activation energy, allowing reactions to occur faster and with less energy.

Coenzyme

A small organic molecule that assists enzyme function (e.g., vitamins).

Cofactor

A non-protein helper (often metal ions) required for enzyme activity.

Competitive inhibitor

A molecule that competes with the substrate for the active site.

Noncompetitive inhibitor

A molecule that binds to another part of the enzyme, changing its shape and reducing function.

Feedback inhibition

A process where the end product of a pathway inhibits an earlier enzyme in that pathway.

Temperature effect on enzyme activity

Activity increases with temperature to a point, then drops if the enzyme denatures.

pH effect on enzyme activity

Each enzyme has an optimal pH; too high or too low can denature it.

Denaturation

The loss of an enzyme’s shape, resulting in loss of function.

Role of enzymes in metabolism

They regulate the rate of all chemical reactions in cells.

Allosteric site

A site other than the active site where molecules can bind and regulate the enzyme.

Enzyme saturation

A state where all active sites are occupied, and adding more substrate doesn’t increase the reaction rate.

Reversibility of enzyme-catalyzed reactions

Many enzymes can catalyze both forward and reverse reactions depending on conditions.