Briefly describe the following methods of regulation of enzyme activity in a cell

i) allosteric control

ii) covalent modification

i) Allosteric control

-Allosteric modulation is a mechanism whereby the activity of an enzyme is either stimulated or inhibited by a compound that binds to a site, called the allosteric site, that is dimensionaly different from the enzyme's active site

ii) Covalent modification

-Covalent modification of enzymes, as illustrated by the addition (or removal) of phosphates, is a general mechanism for changing the activity of enzymes.

-Enzymes that transfer phosphate groups to other proteins are called protein kinases and regulate such diverse activities as hormone action, cell division, and gene expression.