About Human Cells

Human cells contain all the components necessary to sustain life. Not only are the organelles within cells important for function, but the proteins and tissue that connect them are important for cellular communication so that the body can work as a whole. Cells within different tissue create different proteins, but all cells contain the same genetic code throughout the entire body. For instance, a liver cell creates different proteins and has a different function than a cell from kidney tissue.

Overview

• There are categories for organization of cells. Chemical levels involve the bonds and organic functional groups that make up a cell's structure. For instance, blood cells are made up of one heme group and four subunits. This chemical structure is what gives red blood cells the ability to bind to oxygen and deliver it to other parts of the body. Cellular levels make up the functional units of the body. For instance, this level categorizes nerves, muscles, and egg cells. Tissue level categorizes groups of cells that come together to form a specific function. This level includes functional tissue such as connective, nervous, or smooth muscle tissue. Finally, organs make up a group of two or more tissues, and the system level contains multiple organs that create a system such as circulatory or respiratory systems.

Structure

• Human cells are unique from other cells, such as plant cells or bacterial cells. A human cell always contains a membrane and the organelles are also contained within membranous layers. Human cells also have a nucleus where the genetic instructions are translated for protein synthesis. Human cells have linear chromosomes, unlike bacteria, which do not have nucleii and a circular DNA structure.

Mitochondria

• Human cells need energy, and they contain an organelle called the mitochondria that creates the ATP necessary for life. Without ATP, the cell does not have the energy for reactions. The mitochondrion in human cells is the only organelle with its own copy of DNA and internal structure that is separate from the containing cell.

DNA

• Although only some genes are active within certain tissue, every cell in the human body contains an identical, full copy of the genetic code. The human cell contains 46 chromosomes, or 23 pairs. Two of these chromosomes are sex genes; the other 44 are somatic cells that code for all the other functions of the body.

Environment

• The cellular environment is 60 to 90 percent water, one of the most important ingredients in cellular functioning, since it participates in reactions and acts as a solvent. The environment is also ionic, providing many of the action potentials, such as heart beat and movement of food in the esophagus.