Enzymes

General Characteristics

Enzymes are biological catalysts, accelerating biochemical reactions they are involved in.
They are composed primarily of proteins, although some RNA molecules can function as enzymes.
Enzymes are specific in their action as they operate on particular substrates.

Enzyme-Substrate Complex

Enzymes and substrates come together to form an enzyme-substrate complex at the enzyme’s active site; this interaction follows the lock and key model.
The induced fit model suggests the active site changes shape to accommodate the substrate once it binds.
The formation of the enzyme-substrate complex lowers the activation energy of the reaction, speeding up the process.

Influence of Physical Factors

Enzyme activity can be affected by changes in temperature. As temperature increases, so does the rate of reaction, until the optimum temperature is reached. Beyond this, the enzyme denatures.
Enzyme activity is also influenced by the pH of the surroundings. Each enzyme has an optimum pH at which it works best.
Enzyme concentration and substrate concentration affect reaction rate as well. If all other conditions are constant, increasing the concentration of one will increase the rate of reaction until saturation point.

Inhibition of Enzymes

Inhibitors are substances that reduce the activity of enzymes.
Competitive inhibitors resemble the substrate’s structure and compete for the active site, reducing enzyme activity.
Non-competitive inhibitors bind to the enzyme at a different site (allosteric site) changing its shape and preventing substrate binding.

Coenzymes and Cofactors

Coenzymes and cofactors are non-protein components that assist enzymes in performing their function.
Coenzymes are organic molecules and often derived from vitamins, while cofactors are usually metal ions.

By understanding how enzymes function and the factors that can influence their activity, you can assess and predict the outcomes of biochemical reactions in diverse biological contexts.