Cellular Glossary


Macrophage A large mononuclear white cell of the immune system capable of the phagocytosis and killing of invading pathogens. Macrophages are important in the processing and presentation to T cells of microbial antigens for antibody production.

Mast Cell A cell of the immune system that releases the pro-inflammatory compound histamine when injured or confronted by an antigen. Explore the role of mast cells in dust mite allergy.



Meiosis The series of cell divisions in sexual reproduction that lead from a single diploid (2n) cell to four haploid (1n) gametes. View the interactive meiosis animation.

Melanoma A skin cancer of the pigment melanin-producing cells. Explore the dynamics of melanoma cell growth in the Cancer Cell Cam.

Metaphase The stage of mitosis, meiosis I and meiosis II. at which the chromosomes are aligned in a plane (metaphase plate). Metaphase comes after prophase and before anaphase.

Metaphase Checkpoint A point during mitosis when tension of spindle fibers on chromosomes is assessed. If sufficient tension is sensed, the cell is ready to begin moving the chromosomes toward the poles (anaphase). Explore the complete Cell Cycle and associated checkpoints.

Metaphase I Stage within the first of two meiotic divisions when the chromosomes are aligned at the metaphase plate.

Metaphase II Stage within the second of two meiotic divisions when the chromosomes are aligned at the metaphase plate.

Metaphase Plate The central plane of aligned chromosomes during metaphase (mitosis, meiosis I, meiosis II).

Methicillin One of a number of synthetic forms of penicillin meant to kill bacteria, specifically Staphylococcus, that are resistant to penicillin. See also MRSA, below.

MHCII (major histocompatibility complex-2) A protein complex found on the surface of immune cells such as macrophages that present antigenic peptides to t cells with the resulting specific stimulation of the t cell (See MakingAntibodies).



Microbe May be any microscopic organism, but particularly bacteria. Most are not just harmless, they are beneficial and we could not live without them.

Microbiome The total genetic material from a mixed microbial population colonizing a particular environment. The environment could be a place such as a pond or in soil. This term is also used to define the total microbial genetic material in or on a larger organism such on human skin or in an individual’s intestine.

Micron One millionth of a meter. See "HowBig?" for relative microbe sizes.

Microtubules Hollow tubes that are an integral part of the cytoskeleton of eukaryotic cells. They are formed by polymerization of the protein, tubulin.

Mitochondrion (plural: Mitochondria) An organelle of eukaryotic cells that is the site of respiration, energy production and extra-nuclear genes.

Mitosis, M Phase That stage within the cell cycle that active cell division occurs.

Mitotic Spindle The structure in a eukaryotic cell that assembles during mitosis and is responsible for pulling the chromosomes from the metaphase plate to the cell poles during anaphase.

Monoclonal Antibody An antibody produced in a laboratory from a single cloned cell line. Monoclonal antibodies can be produced in large quantities and used for both therapeutic and research purposes. Explore antibody production.

Monolayer A single layer of cells growing on the surface of a tissue culture flask or plate.

MRSA (Methicillin-resistant Staph aureus) A Stahylococcus that has developed resistance to the antibiotic Methicillin and is responsible for infections in humans that are increasingly difficult to combat.

Myocyte Contractile muscle cell of the heart. See myocytes beat.