Therefore, they are important in building, maintaining, and repairing tissues in the human body, especially bone cartilage and muscle. In addition, every cell contains proteins called enzymes, which speed up chemical reactions. Without enzymes, the cells could not function. Certain proteins perform specific jobs. For example, the blood contains such proteins as albumin and hemoglobin.
Albumin helps maintain the body's fluid balance by keeping water in the blood.
Hemoglobin carries oxygen from the lungs to body tissues. Antibodies are proteins in the blood that help protect the body from disease. Chemical substances called hormones, many of which are proteins, control such processes as growth, development, and reproduction. The body obtains most of its energy from carbohydrates and fats. However, the body uses proteins for energy when carbohydrates and fats cannot meet its energy needs.