Cytoplasm

The cytoplasm is the parts of a cell that are enclosed within the plasma membrane. It is eighty percent water and usually clear in color. The cytoplasm is a viscous (thick) gel that liquefies when shaken or stirred. Cytoplasm means cell substance. In eukaryotic cells the cytoplasm contains organelles, such as mitochondria, that are filled with liquid kept separate from the rest of the cytoplasm by biological membranes. It is also the site where most cellular activities occur, such as many metabolic pathways, and processes such as cell division.

The part of the cytoplasm that is not held within organelles is called the cytosol. The cytosol is a complex mixture of cytoskeleton filaments, dissolved molecules, and water that fills much of the volume of a cell. The cytosol is a gel, with a network of fibers dispersed through water. Due to this network of pores and high concentrations of dissolved macromolecules, such as proteins, an effect called macromolecular crowding occurs and the cytosol does not act as an ideal solution. This crowding effect alters how the components of the cytosol interact with each other.

Mitochondrion

A mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. It is sometimes described as the "cellular power plant" because it generates most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Mitochondria provide the energy a cell needs to move, divide, and produce secretory products. They are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type. Mitochondria have been implicated in several human diseases, including mitochondrial disorders and cardiac dysfunction, and may play a role in the aging process.

The number of mitochondria in a cell varies widely by organism and tissue type. Many cells have only a single mitochondrion, whereas others can contain several thousand mitochondria.

The mitochondrion is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, the intermembrane space, the inner membrane, and the cristae and matrix. Mitochondrial proteins vary depending on the tissues and species. In human, 615 distinct types of proteins were identified from cardiac mitochondria.