Question

most enzymes are globular proteins - precise 3d shape. biological catalysts - increase the rate of metabolic reactions without being permanently changed. catalyse anabolic reactions (joining small molecules to make a larger one) as well as catabolic reactions (breaking down molecules). can be reused again and again - a small amount can catalyse a large volume of substrate. act by lowering the activation energy. have an active site - precise 3d shape. each enzyme usually only catalyses one reaction or one group of similar reactions - specificity (due to precise shape of active site). when substrate binds to enzyme to form the enzyme - substrate complex it causes a slight change in the shape of the enzyme = lock and key hypothesis and induced fit. the product is formed and released. name ends in -ase usually e.g. proteases break down protein molecules. can be totally made of protein or contain non - protein parts. if non - protein part is permanent it is called a prosthetic group. if it can be detached it is a coenzyme. what is meant by the term catalyst?

Explanation:

The text defines enzymes as biological catalysts and describes their role in increasing reaction - rates without being altered, which can be generalized to define catalysts.

Answer:

A catalyst is a substance that increases the rate of a metabolic reaction without being permanently changed.