acetyl-coenzyme A
coenzyme complex that holds acetate from pyruvate so it can be oxidized in the citric acid cycle. It also has roles in fatty acid synthesis and other biological processes.
activation energy
minimum energy needed for a chemical reaction to initiate
active site
place on an enzyme where the substrate binds and the reaction occurs
adenosine triphosphate (ATP)
biological unit of energy, which consists of an adenosine (an adenine group and a ribose sugar) and three phosphate groups
aerobic respiration
chemical process in which energy is produced in the presence of oxygen
amphibolic
functional in both catabolic (breaking down molecules to produce energy) and anabolic (building complex compounds that require energy) directions
anabolism
sequence of chemical reactions that constructs or synthesizes molecules from smaller units
apoenzyme
inactive enzyme that requires a cofactor for activation
autotroph
organism that can make its own food
beta oxidation
catabolic process that breaks down fatty acids to produce acetyl-CoA, NADH, and FADH2
catabolism
sequence of chemical reactions that breaks down or decomposes molecules into smaller units while generating energy
catalyst
substance that causes the rate of a chemical reaction to increase
citric acid cycle
series of chemical reactions used by all aerobic organisms to release ATP
coenzyme
nonprotein chemical, such as NAD and FAD, that helps an enzyme function
cofactor
nonprotein compound or metallic ion whose presence is essential for the activity of an enzyme
denaturation
alteration of a protein's shape through some form of external stress, resulting in lack of function
electron transport chain
series of electron transporters that move electrons from NADH and FADH2 to oxygen molecules; protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water
enzyme
substance, usually a protein, that speeds up a biological reaction without being consumed in the reaction
fermentation
anaerobic breakdown of a substance, such as glucose, that produces a limited amount of ATP for a cell
glycolysis
metabolic pathway in which glucose is broken down into pyruvate in the cytoplasm of the cell
heterotroph
organism that obtains energy and carbon from consuming other organisms
holoenzyme
active form of an enzyme that is a complex resulting from the combination of an enzyme and the necessary cofactor(s)
metabolism
sum of biological process that builds or breaks molecules to provide cells with the capacity to acquire and utilize energy
oxidative phosphorylation
production of ATP through chemiosmosis in the mitochondria through an electron transport chain
photosynthesis
process by which autotrophs convert light energy into chemical energy that is stored in organic compounds such as sugars
proton gradient
pathway in which protons move from an area of higher concentration to an area of lower concentration
redox reaction
reaction that involves the transfer of electrons between two atoms or molecules
substrate
molecule that is acted upon by an enzyme by binding to the enzyme's active site