Understanding Enzymes and Metabolic Reactions

Endergonic Reaction

A chemical reaction that requires an input of energy to proceed; energy is absorbed, and products have more energy than reactants.

Exergonic Reaction

A chemical reaction that releases energy; products have less energy than reactants.

Metabolic Pathway

A series of chemical reactions in a cell, each catalyzed by a specific enzyme, that build up or break down molecules.

Metabolism

The sum of all chemical reactions in an organism, including anabolic and catabolic pathways.

Identifying Endergonic and Exergonic Reactions

In a graph, endergonic reactions will show a net increase in energy, with products at a higher energy level than reactants. Exergonic reactions will show a net decrease in energy, with products at a lower energy level than reactants.

Catabolic Reactions

Break down molecules and release energy, typically exergonic.

Anabolic Reactions

Build up molecules and require an energy input, typically endergonic.

Activation Energy

The minimum energy required to start a chemical reaction.

Catalyst

A substance that speeds up a chemical reaction without being consumed.

Energy Barrier

The activation energy needed to initiate a reaction.

Enzyme

A biological catalyst that lowers the activation energy of reactions.

Why Cells Need Enzymes

Enzymes speed up reactions by lowering the activation energy, allowing essential biochemical reactions to occur efficiently at body temperatures.

Enzyme and Activation Energy

Enzymes lower the activation energy needed for reactions, making it easier for reactants to reach the transition state and become products.

Activation Energy (Graph)

Peak of the curve above the reactants' energy level.

Exergonic/Endergonic Reaction (Graph)

If the products have less energy than reactants, it's exergonic; if products have more, it's endergonic.

Reactants and Products (Graph)

Label the initial energy level as reactants and the final level as products.

Active Site

The region on an enzyme where the substrate binds.

Allosteric Site

A site on an enzyme where a molecule can bind, changing the enzyme's shape and activity.

Cofactors

Inorganic substances that assist enzymes in catalyzing reactions.

Coenzymes

Organic molecules that assist enzymes.

Induced Fit

The change in shape of an enzyme's active site when a substrate binds.

Substrate

The reactant molecule that binds to an enzyme's active site.

Enzyme Structure and Specificity

The 3D shape of an enzyme, particularly the active site, is specific to the substrate, allowing only certain substrates to bind.

Catalytic Cycle

The process involving substrate binding, catalysis, and product release.

Factors Affecting Enzyme Function

Temperature, pH, substrate concentration, and inhibitors can all affect enzyme activity.

Inhibitors

Molecules that decrease enzyme activity, either by blocking the active site (competitive inhibitors) or altering the enzyme's shape (non-competitive inhibitors).