acetyl CoA combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B-group vitamin)

activation energy energy necessary for reactions to occur

aerobic respiration process in which organisms convert energy in the presence of oxygen

anabolic (also, anabolism) pathways that require an input of energy to synthesize complex molecules from simpler ones

anaerobic process that does not use oxygen

anaerobic cellular respiration process in which organisms convert energy for their use in the absence of oxygen

ATP adenosine triphosphate, the cell’s energy currency

ATP synthase (also, F1F0 ATP synthase) membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it

bioenergetics study of energy flowing through living systems

catabolic (also, catabolism) pathways in which complex molecules are broken down into simpler ones

chemical energy potential energy in chemical bonds that is released when those bonds are broken

chemiosmosis process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane

citric acid cycle (also, Krebs cycle) series of enzyme-catalyzed chemical reactions of central importance in all living cells

dephosphorylation removal of a phosphate group from a molecule

endergonic describes chemical reactions that require energy input

enthalpy total energy of a system

entropy (S) measure of randomness or disorder within a system

exergonic describes chemical reactions that release free energy

fermentation process of regenerating NAD+ with either an inorganic or organic compound serving as the final electron acceptor, occurs in the absence; occurs in the absence of oxygen

free energy Gibbs free energy is the usable energy, or energy that is available to do work.

glycolysis process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

heat energy energy transferred from one system to another that is not work (energy of the motion of molecules or particles)

heat energy total bond energy of reactants or products in a chemical reaction

isomerase enzyme that converts a molecule into its isomer

kinetic energy type of energy associated with objects or particles in motion

Krebs cycle (also, citric acid cycle) alternate name for the citric acid cycle, named after Hans Krebs who first identified the steps in the pathway in the 1930s in pigeon flight muscles; see citric acid cycle

metabolism all the chemical reactions that take place inside cells, including anabolism and catabolism

oxidative phosphorylation production of ATP using the process of chemiosmosis and oxygen

phosphoanhydride bond bond that connects phosphates in an ATP molecule

phosphorylation addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP

potential energy type of energy that has the potential to do work; stored energy

prosthetic group (also, prosthetic cofactor) molecule bound to a protein that facilitates the function of the protein

pyruvate three-carbon sugar that can be decarboxylated and oxidized to make acetyl CoA, which enters the citric acid cycle under aerobic conditions; the end product of glycolysis

redox reaction chemical reaction that consists of the coupling of an oxidation reaction and a reduction reaction

substrate-level phosphorylation production of ATP from ADP using the excess energy from a chemical reaction and a phosphate group from a reactant

TCA cycle (also, citric acid cycle) alternate name for the citric acid cycle, named after the group name for citric acid, tricarboxylic acid (TCA); see citric acid cycle

thermodynamics study of energy and energy transfer involving physical matter

transition state high-energy, unstable state (an intermediate form between the substrate and the product) occurring during a chemical reaction

ubiquinone soluble electron transporter in the electron transport chain that connects the first or second complex to the third