Zoology MCQs for NEET — Practice Questions with Answers

The correct answer is 'Lock & key.' The 'lock and key' model describes the specificity of enzymes and substrates. Just like a key fits into a specific lock, a substrate fits into the active site of an enzyme. This analogy illustrates that enzymes are highly specific to their substrates, and this specificity is due to the unique shape and chemical environment of the enzyme's active site.

The correct answer is 'Sucrase.' Sucrase is an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose. Unlike triglycerides, cellulose, and galactose, which are not enzymes, sucrase is a biological molecule that speeds up a specific biochemical reaction.

Lysosomes are membrane-bound organelles that contain hydrolytic enzymes responsible for breaking down waste materials and cellular debris. These enzymes are capable of digesting various macromolecules, making lysosomes the primary site for intracellular digestion.

Enzymes are typically named after the substrate they act upon, with the suffix '---ase' added to the root name of the substrate. For example, the enzyme that breaks down lactose is called lactase. This naming convention helps in identifying the function of the enzyme based on its name.

The active site of an enzyme is the region where substrate molecules bind and undergo a chemical reaction. It is specifically shaped to fit the substrate, facilitating the conversion of the substrate into the product. The product is then released from the active site once the reaction is complete.

Hexokinase is the enzyme that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the presence of ATP. This is the first step in glycolysis and is a key regulatory point in the metabolic pathway.

Isomerase is the enzyme responsible for converting glucose-6-phosphate to fructose-6-phosphate. Specifically, the enzyme phosphoglucose isomerase (also known as glucose phosphate isomerase) facilitates this reaction during glycolysis.

Maltase is the enzyme that catalyzes the hydrolysis of maltose into two glucose molecules. This reaction is essential for the digestion of carbohydrates in the human body.

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.