Science / Biology Glossary
Chemiosmosis: The process by which ATP is produced in the inner membrane of a mitochondrion. The electron transport system transfers protons from the inner compartment to the outer; as the protons flow ba . . . View Full Definition
Chemotrophs: Organisms (usually bacteria) that derive energy from inorganic reactions; also known as chemosynthetic.
Chiasma: The site where the exchange of chromosome segments between homologous chromosomes takes place (crossing-over) (pl.: chiasmata).
Chitin: A polysaccharide contained in fungi; also forms part of the hard outer covering of insects.
Chlamydia: A sexually transmitted disease caused by a parasitic bacterium that lives inside cells of the reproductive tract.
Chlorofluorocarbons (CFCS): Chemical substances used in refrigerators, air conditioners, and solvents that drift to the upper stratosphere and dissociate. Chlorine released by CFCs reacts with ozone, eroding the ozone layer.
Chlorophyll: The pigment in green plants that absorbs solar energy.
Chlorophyll A: The green photosynthetic pigment common to all photosynthetic organisms.
Chlorophyll B: An accessory chlorophyll found in green algae and plants.
Chlorophyll C: An accessory chlorophyll found in some protistans.
Chlorophyta: The taxonomic division that contains what are commonly called the green algae.
Chloroplasts: Disk-like organelles with a double membrane found in eukaryotic plant cells; contain thylakoids and are the site of photosynthesis. ATP is generated during photosynthesis by chemiosmosis.
Cholecystokinin: A hormone secreted in the duodenum that causes the gallbladder to release bile and the pancreas to secrete lipase.
Chorion: The two-layered structure formed from the trophoblast after implantation; secretes human chorionic gonadotropin.
Chorionic Villi Sampling (CVS): A method of prenatal testing in which fetal cells from the fetal side of the placenta (chorionic villi) are extracted and analyzed for chromosomal and biochemical defects.
Chromatid: Generally refers to a strand of a replicated chromosome; consists of DNA and protein.
Chromatin: A complex of DNA and protein in eukaryotic cells that is dispersed throughout the nucleus during interphase and condensed into chromosomes during meiosis and mitosis.
Chromosome Theory Of Inheritance: Holds that chromosomes are the cellular components that physically contain genes; proposed in 1903 by Walter Sutton and Theodore Boveri.
Chromosomes: Structures in the nucleus of a eukaryotic cell that consist of DNA molecules that contain the genes.
Chrysophytes: Protistan division that is referred to as the golden brown algae; includes the diatoms.
Cilia: Hair-like organelles extending from the membrane of many eukaryotic cells; often function in locomotion (sing.: cilium).
Circadian Rhythms: Biorhythms that occur on a daily cycle.
Circulatory System: One of eleven major body organ systems in animals; transports oxygen, carbon dioxide, nutrients, and waste products between cells and the respiratory system and carries chemical signals from . . . View Full Definition
Classes: Taxonomic subcategories of phyla.
Clavicle: The collar bone.