The embryonic endoderm<span> develops into the interior linings of two tubes in the body, the digestive and respiratory tube. the </span>lining<span> of the follicles of the thyroid gland and the</span>epithelial<span> component of the thymus (i.e. thymic </span>epithelial<span> cells). Liver and pancreas cells are believed to </span>derive<span> from a common precursor.</span>
An active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. The substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme