Question

enzymes are substances that catalyze chemical reactions. a change in the ph of the medium is known to decrease the activity of an enzyme. which statement explains how a change in ph affects the activity of an enzyme?
it alters the shape of the enzyme.
it alters the concentration of the enzyme.
it alters the solubility of the enzyme.
it alters the density of the enzyme.

Explanation:

Enzymes are proteins with a specific three - dimensional structure, including an active site. The pH of the medium can affect the ionization state of amino acid residues in the enzyme. This change in ionization can disrupt the weak bonds (such as hydrogen bonds, ionic bonds) that maintain the enzyme's specific three - dimensional structure, including the shape of the active site. A change in the shape of the enzyme (specifically the active site) can lead to a decrease in enzyme activity as the substrate may no longer be able to bind effectively or the catalytic mechanism may be disrupted. Changing the pH does not directly alter the concentration, solubility (in a simple direct way related to enzyme activity alteration), or density of the enzyme in a way that explains the decrease in enzyme activity.

Answer:

It alters the shape of the enzyme.