Same is in the case of body's metabolism. You intake a balanced diet but you don't have the proper channel for the digestion of the nutrients. Do you think the purpose of your diet will get served? Very likely the body's metabolic function too needs a proper catalytic action to generate more energy and meet the body's requirement. What is responsible for all these functions? To serve the body's different metabolic activities, the catalytic function is of course played by the enzymes. The rule is same for all animals.

Catalyst in the digestive system

-Among the key nutrients of the food taken, carbohydrate and protein molecules are broken into minute particles with the help of enzymes. Unless these molecules are brought down to such a position they cannot be absorbed by the walls of the small intestine for the further process. Starch cannot be digested as it is. Actually the complex molecules in the form of a chain are made into simpler forms like maltose for the absorption process to take place. Only can then your consumed food will be able to provide energy to your body. This is one way enzyme takes part of the of the body's metabolic activities.

-There is no need to think that enzymes are only required by the human beings. In the broader perspective both the food habits of feeding on flesh and fibers as well as healthy green leafy herbs, you need enzymes for digestive and metabolic activities. The animals those are exclusively herbivorous like the cows, goats, horses etc need a special type of enzyme for digestion process. The cell wall of the plant fibers is composed of cellulose. For the decomposition of cellulose the enzyme needed is cellulase.

Direction for metabolic chain reaction

The metabolic process of glycolysis occurring in the cell largely depends on the enzymes to take place. Without the support of the enzymes the entire chain reaction in the metabolic activity cannot be directed. The reaction of ATP with glucose to generate glucose-6-phosphate in the presence of hexokinase within in a cell is entirely dependent on the functional enzymes.

Thus as cell is the basic unit of any living organism and the core of metabolism begins from here, you can well understand how important are enzymes for the metabolic activity of the whole system.