Enzymes are proteins. Proteins are long chains of amino acids linked to each other by peptide bonds. Amino acids have many functional groups in their structure. Many of these functional groups are ionisable. As they are weak acids and bases in chemical nature,this ionisation is influenced by the $pH$ of the solution. For many enzymes,activity is influenced by the surrounding $pH$. This is depicted in the curve below. Explain briefly.

(N/A) The curve shows that enzyme activity is dependent on the $pH$ of the surrounding medium.
$1$. Enzymes exhibit maximum activity at a specific $pH$ value,known as the optimum $pH$.
$2$. As the $pH$ moves away from this optimum value (either towards more acidic or more basic conditions),the ionisation state of the amino acid residues in the enzyme's active site changes.
$3$. This alteration in the ionisation state affects the enzyme's tertiary structure and the binding of the substrate to the active site,leading to a decrease in catalytic activity.
$4$. Extreme $pH$ values can cause denaturation of the enzyme,resulting in a complete loss of activity.