Enzymes

Enzymes are chemicals that speed up reactions without being consumed. Catalase, found in almost all living cells, breaks down hydrogen peroxide (H2O2) into water and oxygen. Hydrogen peroxide is naturally produced in cells and must be broken down to prevent cellular damage. Catalase performs this breakdown incredibly fast, processing 40 million H2O2 molecules per second.

An enzyme is a giant protein with an active site, a specific area where the substrate (e.g., H2O2 for catalase) fits, much like a key fits a lock. The enzyme then chemically 'tugs' on the substrate, lowering its activation energy and facilitating its breakdown into products. Without an enzyme, this breakdown would take millions of years, but with an enzyme, it happens in seconds.

Enzymes can be turned on or off. Activation can occur by producing the enzyme only when needed (gene regulation) or by adding activators. Activators include cofactors (inorganic chemicals like heme with iron) and coenzymes (organic chemicals like thiamine/vitamin B1). These are essential for the enzyme to function; without them, the enzyme remains inactive or ceases to function, highlighting their importance for life.

Enzymes can also be turned off through inhibition. Competitive inhibition occurs when an inhibitor chemical blocks the active site, preventing the substrate from binding. Allosteric (non-competitive) inhibition involves an inhibitor binding to a different site on the enzyme (allosteric site). This can either cover the active site or change its shape, making it impossible for the substrate to bind, thus stopping the reaction.

Enzyme activity can be measured by monitoring the production of products or the consumption of reactants. For example, in a catalase lab, the rate of oxygen production indicates enzyme activity. Factors like enzyme concentration, temperature, and pH affect reaction rates. Organisms maintain optimal internal conditions (e.g., 37 degrees Celsius for humans) because enzymes are prime to work efficiently within specific ranges; extreme conditions can denature enzymes and halt their function.