Glossary of Terms - Mitochondria Studies

It might be helpful to look over these terms before studying mitochondria function on this web site.

artifact. In reference to a recording, an artifact is an observed change that is not due to the experimental intervention. For example, a spike in a record due to a power surge would be an artifact.

cellular respiration. The consumption of oxygen and generation of carbon dioxide by mitochondria.

citric acid. Consisting of six carbon atoms and associated hydrogen and oxygen, the most reduced of the Krebs substrates.

coenzyme. A molecule that is associated with an enzyme, and necessary for it to function, but that is itself without catalytic activity.

coenzyme A. Derived from pantothenic acid (one of the B vitamins), it is used to conserve energy in several metabolic reactions.

coupled reaction. An enzyme-catalyzed reaction in which an exergonic reaction is linked to an endergonic reaction or process, conserving some free energy.

crista (pl., -ae). Specialized folds of the inner membrane of mitochondria.

electron transport system (ETS). Electron carrier complexes and individual carriers embedded in the inner membrane of mitochondria and in thylakoid membranes of chloroplasts. Responsible for the conservation of energy by electron transport.

endergonic reaction. An energy-requiring reaction - not spontaneous.

enzyme. A protein that is designed to catalyze specific chemical reactions in living cells.

ETS. (see: electron transport system).

eukaryotic cell (eukaryote, also eucaryote). A cell posessing a true nucleus. The cells of members of all kingdoms but Monera are eukaryotic.

exergonic reaction. A spontaneous chemical reaction - one that releases energy.

FAD. (see: flavin adenine dinucleotide).

flavin adenine dinucleotide (FAD). An energy carrier from succinate to complex II of the electron transport system. Actually part of complex II. Synthesized from the vitamin riboflavin (B2).

free energy. The total energy of a system that is available to do work under constant conditions of temperature and pressure.

intermembrane space. The compartment between the inner and outer membranes of mitochondria.

Krebs cycle (Citric acid cycle). The sequential (and cyclic) oxidation of substrates and conservation of energy by enzymes of the mitochondrial matrix.

matrix (of mitochondria). The compartment surrounded by the inner membrane of mitochondria.

membrane. A specialized phospholipid bilayer with associated proteins that delineates the boundaries of cells and organelles.

mitochondrion (pl. -dria). The organelle that is responsible for cellular respiration in eukaryotes. The cellular 'power plant' that is responsible for production of ATP by oxidative metabolism.

NAD. (see: nicotinamide adenine dinucleotide)

nicotinamide adenine dinucleotide (NAD). An energy carrier molecule, used directly by enzymes or to shuttle energy to the electron transport system. Synthesized from the vitamin niacin (nicotinic acid).

organelle. A distinct compartment within a cell, created by the organization of cellular membranes (examples: mitochondrion, chloroplast, endoplasmic reticulum, Golgi apparatus, flagellum).

oxaloacetate (oxaloacetic acid). Consisting of four carbon atoms and associated hydrogen and oxygen, the most oxidized of the Krebs substrates.

oxidation. 1. The combination of oxygen with a molecule with liberation of heat; combustion. 2. Removal of hydrogen from a molecule. 3. Loss of electrons, increasing the positive valence. Oxidation is associated with a loss of energy.

reduction (chemical). A reaction involving the gain of electrons, addition of hydrogen atoms, or loss of oxygen atoms. Reduction is associated with a gain of energy.

State III respiration. ADP-stimulated respiration by isolated mitochondria. State IV respiration. Respiration by isolated mitochondria in the resting, or idling, state - in the absence of ADP or any of the metabolic poisons or uncoupling agents. substrate (metabolic). A reactant that is chemically modified by an enzyme.