NEET Practice Questions (MCQs) with Answers & Solutions

Dihydroxyacetone is the only monosaccharide that does not have a chiral center, and hence, it does not show optical isomerism. Optical isomerism requires at least one chiral carbon, which dihydroxyacetone lacks.

Isomerases are enzymes that catalyze the conversion of a molecule into one of its isomers. They facilitate the rearrangement of atoms within the molecule, which is essential for various metabolic pathways.

Digestive enzymes are the best example of extracellular enzymes because they are secreted by cells and function outside the cell to break down large food molecules into smaller, absorbable units.

A non-protein component of an enzyme is called a co-factor. Co-factors can be metal ions or organic molecules that assist in the enzyme's activity. They are crucial for the proper functioning of enzymes.

Carbonic anhydrase is activated in the presence of zinc (Zn). Zinc acts as a co-factor and is essential for the catalytic activity of carbonic anhydrase, which is responsible for the reversible conversion of carbon dioxide and water to bicarbonate and protons.

Vanadium is necessary for the activation of the enzyme nitrogenase. Nitrogenase is an enzyme complex that catalyzes the fixation of atmospheric nitrogen (N₂) into ammonia (NH₃) and requires vanadium as a co-factor for its activity.

Enolase is an enzyme that is activated by magnesium (Mg), manganese (Mn), and zinc (Zn) ions. These cofactors are essential for the proper functioning and stabilization of the enzyme's active site, which is crucial for its catalytic activity in the glycolytic pathway.

ADP (Adenosine Diphosphate) is not a co-enzyme. Co-enzymes are organic molecules that bind to the active sites of certain enzymes to assist in the catalysis of reactions. Examples include NAD (Nicotinamide Adenine Dinucleotide), NADP (Nicotinamide Adenine Dinucleotide Phosphate), and FAD (Flavin Adenine Dinucleotide), which are all involved in redox reactions. ADP, on the other hand, is a substrate involved in energy transfer.

Calcium ions (Ca²⁺) play a significant role in the activation of certain enzymes. Nitric oxide synthase, protein phosphatase, and adenylate kinase are all activated by calcium ions. These enzymes are involved in various cellular processes, including signal transduction, metabolic regulation, and nitric oxide production.

Coenzymes are organic molecules that bind to the enzyme and help in the enzymatic activity. Unlike prosthetic groups, which are tightly bound to the enzyme, coenzymes bind loosely and can dissociate from the enzyme after the reaction. This characteristic allows coenzymes to be used by multiple different enzymes.