Chemical Reactions & Enzymes Overview

Overview

This lecture reviews chemical reactions and enzymes, focusing on the definitions, types of reactions, enzyme function, specificity, and regulation.

Chemical reactions convert one substance into another by creating or breaking chemical bonds.
Reactions typically build larger substances from smaller ones (synthesis) or break larger substances into smaller ones (decomposition).
Synthesis (anabolic) reactions join two or more smaller substances to make a larger substance (e.g., protein synthesis, ATP formation).
Decomposition (catabolic) reactions break down larger substances into their parts (e.g., sugar breakdown, ATP to ADP).

Enzymes are three-dimensional proteins made from DNA instructions and are not consumed in reactions.
Enzymes act as catalysts, speeding up reactions and lowering the energy required (activation energy).
Enzymes can be reused multiple times.

Enzymes have specific active sites that bind only to particular substrates.
Substrates are the specific molecules enzymes act on.
Enzyme specificity ensures only certain substrates bind, determined by the shape of the active site.
Enzyme affinity describes the strength of attraction between an enzyme and its substrate, affected by cellular conditions.

Cofactors and coenzymes are molecules that turn enzymes on or off, affecting their ability to bind substrates.
Presence of an enzyme greatly reduces the activation energy needed for reactions.

Substrates approach and bind to the enzyme's active sites, forming an enzyme-substrate complex.
The enzyme facilitates substrate interaction, leading to product formation.
Products are released, and the enzyme returns to its original form for reuse.

Chemical Reaction — Conversion of one substance into another via chemical bond changes.
Synthesis (Anabolic) Reaction — Joining small molecules to form a larger one.
Decomposition (Catabolic) Reaction — Breaking down a large molecule into smaller ones.
Enzyme — Protein that speeds up reactions and lowers activation energy.
Catalyst — Substance that increases the rate of a reaction without being consumed.
Active Site — Specific region on an enzyme where substrates bind.
Substrate — Molecule an enzyme acts upon.
Enzyme Specificity — Ability of an enzyme to bind only certain substrates.
Enzyme Affinity — Strength of binding between enzyme and substrate.
Cofactor/Coenzyme — Molecule that activates or deactivates an enzyme.