Cells are basic units of all living things, including bacteria, plants and animals. The human body is composed entirely of cells, fluids and cellular products. As the basic functional units, the cells carry on life processes. Cells also have the ability to reproduce, providing new ones for growth and replacement of worn and injured tissues.
Cells are made up of protoplasm, a colorless jellylike substance in which food elements such as protein, fats, carbohydrates, mineral salts and water are present. The principal parts of a cell are the cytoplasm, centrosome, nucleus, nucleolus and cell membrane. The thin cell membrane or cell wall permits soluble or dissolvable substances to enter and leave the protoplasm. The nucleus near the center of the cell, is contained in a nuclear membrane. Outside of the nucleus are the cytoplasm and the centrosome. The nucleus and the cytoplasm are made up of protoplasm. The centrosome and the nucleus control cell reproduction.
As long as the cell receives an adequate supply of food, oxygen and water, eliminates waste products and is favored with proper temperature; it will continue to grow and thrive. However, if these conditions do not exist and there is the presence of toxins or pressure, then the growth and health of the cells are impaired. Most body cells are capable of growth and self-repair during their life cycle.
Metabolism is a complex chemical process whereby the body cells are nourished and supplied with the energy needed to carry on their many activities. There are two phases of metabolism.
Anabolism is the process of building up larger molecules from smaller ones. During this process the body stores food, water and oxygen for the time when these substances are needed for cell growth and repair. Catabolism is the breaking down of larger substances or molecules into smaller ones. This process releases energy that can be stored by special molecules, which is used for muscle contraction, secretion and heat production.
Anabolism and catabolism are carried out simultaneously and continuously within the cells. Their activities are closely regulated so that the breaking down, energy-releasing reactions are balanced with the building up energy-consuming reactions. Therefore, homeostasis or the maintenance of normal, internal stability within the organism is maintained. However, if we use less energy than we manufacture, we may experience weight gain. If the molecules of energy are not used, they turn to fat. To get rid of the buildup fat, more energy or exercise must be used or less energy or food, must betaken in.