Matrix (biology)

For the journal, see Matrix Biology (journal).

In biology, matrix (plural: matrices) is the material (or tissue) in animal or plant cells, in which more specialized structures are embedded, and a specific part of the mitochondrion that is the site of oxidation of organic molecules. The internal structure of connective tissues is an extracellular matrix. Finger nails and toenails grow from matrices. It is found in various connective tissue. It is generally used as a jelly like structure instead of cytoplasm in connective tissue.

Tissue matrices

Extracellular matrix

Main article: Extracellular matrix

The main ingredients of the extracellular matrix are glycoproteins secreted by the cells. (Recall that glycoproteins are proteins with covalently bound carbohydrates, usually short chains of sugars.) The most abundant glycoprotein in the ECM of most animal cells is collagen, which forms strong fibers outside the cells. In fact, collagen accounts for about 40% of the total protein in the human body. The collagen fibers are embedded in a network woven from proteoglycans. A proteoglycan molecule consists of a small core protein with many carbohydrate chains covalently attached, so that it may be up to 95% carbohydrate. Large proteoglycan complexes can form when hundreds of proteoglycans become noncovalently attached to a single long polysaccharide molecule. Some cells are attached to the ECM by still other ECM glycoproteins such as fibronectin. Fibronectin and other ECM proteins bind to cell surface receptor proteins called integrins that are built into the plasma membrane. Integrins span the membrane and bind on the cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. The name integrin is based on the word integrate, integrins are in a position to transmit signals between the ECM and the cytoskeleton and thus to integrate changes occurring outside and inside the cell. Current research on fibronectin, other ECM molecules, and integrins is revealing the influential role of the ECM in the lives of cells. By communicating with a cell through integrins, the ECM can regulate a cell's behavior. For example, some cells in a developing embryo migrate along specific pathways by matching the orientation of their microfilaments to the "grain" of fibers in the ECM. Researchers are also learning that the ECM around a cell can influence the activity of genes in the nucleus. Information about the ECM probably reaches the nucleus by a combination of mechanical and chemical signaling pathways. Mechanical signaling involves fibronectin, integrins, and microfilaments of the cytoskeleton. Changes in the cytoskeleton may in turn trigger chemical signaling pathways inside the cell, leading to changes in the set of proteins being made by the cell and therefore changes in the cells function. In this way, the ECM of a particular tissue may help coordinate the behavior of all the cells within that tissue. Direct connections between cells also function in this coordination.

Bone matrix

Main article: Osteon

Bone is a form of connective tissue found in the body and has a storage area, or osteon region, also called matrix that allows mineral salts such as calcium to be stored and transported.

Subcellular matrices

Mitochondrial matrix

Main article: Mitochondrial matrix

In the mitochondrion, the matrix contains soluble enzymes that catalyze the oxidation of pyruvate and other small organic molecules.

Nuclear matrix

Main article: Nuclear matrix

In the cell nucleus the matrix is the insoluble fraction that remains after extracting the solubled DNA.

Golgi matrix

The Golgi matrix is a protein scaffold made up of golgins on the cytoplasmic side of the Golgi apparatus involved in keeping its shape and membrane stacking.

Matrix (medium)

A matrix is also a medium in which bacteria are grown (cultured). For instance, a Petri dish of agar may be the matrix for culturing a sample swabbed from a patient's throat.

See also

• Matrix biology
• Matricity

Tissues and cells

• Germinal matrix
• Hair matrix cell

Molecular biology

• Matrix attachment region
• Matrix metalloproteinase
• Matrix protein

Bioinformatics and sequence evolution

• PAM matrix
• Position-specific scoring matrix
• Similarity matrix
• Substitution matrix

Botany and agriculture

• Matrix Planting

Population biology and ecology

• Matrix population models