Vitamins are the organic compounds required in the diet in small amounts to perform specific biological functions for normal maintenance of optimum growth and health of the organism. Vitamins are classified into two groups depending on their solubility in water or fat. Vitamins which are soluble in fat and oils but insoluble in water are fat-soluble vitamins. Fat-soluble vitamins are vitamins A, D, E and K. Fat-soluble vitamins are stored in the liver and adipose tissues. Vitamins of B group and vitamin C are soluble in water and are known as water-soluble vitamins. Water-soluble vitamins must be supplied regularly in the diet because they are readily excreted in urine and cannot be stored (except vitamin B₁₂) in our body. Plants can synthesize all vitamins whereas only a few vitamins like vitamin K, vitamin A from carotene, and some members of the vitamin B complex are synthesized in the human body. Vitamins catalyze biological reactions in very low concentrations. Multiple deficiencies caused by a lack of more than one vitamin are called avitaminosis.

The function of enzyme in the living system is to

catalyze biochemical reactions

The correct answer is option 3. catalyze biochemical reactions.

Let us explore the role of enzymes and how they fit into the broader context of biological functions.

Catalysis and Enzyme Function:

Catalysts: Enzymes are biological catalysts. A catalyst is a substance that increases the rate of a chemical reaction without being consumed or permanently altered by the reaction.

Enzymes: Enzymes are specific proteins that catalyze biochemical reactions in living organisms. They accelerate reactions by lowering the activation energy, which is the energy required to initiate the reaction. This makes the reaction proceed faster than it would without the enzyme.

Mechanism of Action:

Active Site: Enzymes have a specific region called the active site where the substrate (the molecule undergoing the reaction) binds. The enzyme-substrate complex forms, allowing the reaction to occur more efficiently.

Enzyme Specificity: Each enzyme is specific to a particular substrate or type of reaction. This specificity is due to the unique shape and chemical environment of the active site.

Role in Biochemical Reactions:

Metabolism: Enzymes are central to metabolic pathways, which include both catabolic reactions (breaking down molecules to release energy) and anabolic reactions (building complex molecules using energy). For example:

Digestive Enzymes: Enzymes like amylase, protease, and lipase break down carbohydrates, proteins, and fats, respectively, into their constituent molecules so they can be absorbed and utilized by the body.

Cellular Respiration: Enzymes are involved in the breakdown of glucose to produce ATP, the energy currency of the cell.

Why Other Options Are Not Functions of Enzymes:

Transport Oxygen: This is primarily the role of hemoglobin in the blood, which binds to and transports oxygen from the lungs to tissues and organs.

Provide Immunity: Immunity is supported by components such as antibodies, immune cells (like T-cells and B-cells), and various immune system molecules, rather than enzymes.

Provide Energy: Enzymes themselves do not provide energy but facilitate the reactions that release or utilize energy. For instance, enzymes help in processes like glycolysis and the Krebs cycle, which are involved in energy production.

Summary: Enzymes are crucial for speeding up biochemical reactions in living organisms. By lowering the activation energy required for reactions to proceed, they enable vital processes such as digestion, metabolism, and synthesis of biomolecules. Their ability to catalyze specific reactions makes them essential for maintaining life functions.

Thus, the correct role of enzymes is to: Catalyze biochemical reactions.