They are regulator molecules. They regulate normal growth and development.
Vitamin A regulates normal eye function, vitamin D regulates normal growth of bone, and vitamin C is needed for immunity or body defense. They do not provide energy.
Enzymes
They are biological catalysts. Enzymes speed up biochemical reactions.
Without enzymes life processes would be very slow. There are many enzymes in our body, such as pepsin, which acts in protein digestion in the stomach.
Hormones
They are chemical messengers in organisms. They carry messages from one organ to another organ, or to all of the body's organs. Hormones regulate normal body functions. Insulin is a hormone that carries a message from the pancreas to body cells in order to balance the glucose level in the blood.