A type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell. A build up of reactive oxygen species in cells may cause damage to DNA, RNA, and proteins, and may cause cell death. Reactive oxygen species are free radicals. Also called oxygen radical.
A family of enzymes that occur in all living organisms and are thought to regulate cellular aging, apoptosis, and resistance to stress in more complex eukaryotic organisms.
A substance from which another is formed, especially by metabolic reaction.
Nicotinamide adenine dinucleotide (NAD) is a molecule present in all cells that participates in many metabolic reactions.
(Mitochondrion) An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.
Any substance produced during metabolism.
The sum of the processes by which a particular substance is handled in the living body.
The length of time in one’s life where one is spent in optimal health.
Enzymes are complex proteins that speed biochemical reactions. Enzymes can build up or break down other molecules. The molecules they act on are called substrates. Enzymes are catalysts—chemicals that hasten a chemical reaction without undergoing any change themselves.
A substance that enhances the action of an enzyme. Coenzymes are small molecules. They cannot by themselves catalyze a reaction but they can help enzymes to do so. In technical terms, coenzymes are organic nonprotein molecules that bind with the protein molecule to form the active enzyme.
Adenosine 5′-triphosphate, or ATP, is the principal molecule for storing and transferring energy in cells. It is often referred to as the energy currency of the cell and can be compared to storing money in a bank. ATP can be used to store energy for future reactions or be withdrawn to pay for reactions when energy is required by the cell.