Metabolism and Cellular Respiration Vocabulary

aerobic respiration

A catabolic pathway for organic molecules, using oxygen as the final electron acceptor in an electron transport chain and ultimately producing ATP. This is the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms

Fermentation

A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid

citric acid cycle

A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA to carbon dioxide; occurs within the mitochondria in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration

redox reaction

A chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another

ATP-Synthase

A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentration gradient to make ATP. These are found in the inner mitochondrial membrane of eukaryotic cells and in the plasma membranes of prokaryotes

anabolic pathway

A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules

catabolic pathway

A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules

beta oxidation

A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA

phosphorylated intermediate

A molecule with a phosphate group covalently bound to it, making it more reactive than the unphosphorylated molecule

electron transport chain

A sequence of electron carrier molecules that shuttle electrons down a series of redox reactions that release energy used to make ATP

glycosis

A series of reactions that ultimately splits glucose into pyruvate. This occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration

facultative anaerobes

An organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present

obligate anaerobes

An organism that only carries out fermentation or anaerobic respiration. Such organisms cannot use oxygen and in fact may be poisoned by it

alcohol fermentation

Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide

latic acid fermentation

Glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide

NAD+

Nicotinamide adenine dinucleotide, a coenzyme that cycles easily between oxidized and reduced states, thus acting as an electron carrier

allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site

energy

The capacity to cause change, especially to do work

cellular respiration

The catabolic pathway of aerobic and anaerobic respiration, which breaks down organic molecules and use an electron transport chain for the production of ATP

potential energy

The energy that matter possesses as a result of its location or spatial arrangement

substrate-level phosphorylation

The enzyme catalyzed formation of ATP by direct transfer of phosphate group to ADP from an intermediate substrate in catabolism

proton-motive force

The potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis

second law of thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat

oxidative phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration

catalyst

a chemical agent that selectively increases the rate of a reaction without being consumed by the reaction

enzyme

a macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction

entropy

a measure of disorder or randomness.

feedback inhibition

a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway

Adennosine Triphosphate

a molecule that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in the cells

endergonic reaction

a nonspontaneous chemical reaction in which free energy is absorbed from the surroundings

metabolic pathway

a series of chemical reactions that either builds a complex molecule or breaks down a complex molecule to simpler molecules

exergonic reaction

a spontaneous chemical reaction in which there is a net release of free energy

noncompetitive inhibitor

a substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product

Competive inhibitors

a substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics

enzyme-substrate complex

a temporary complex formed when an enzyme binds to its substrate molecules

chemosmosis

an energy coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Under aerobic conditions, most ATP synthesis occurs this way

cytochromes

an iron-containing protein that is component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells

coenzyme

an organic molecule serving as a cofactor

cofactors

any nonprotein molecule or ion that is required for the proper functioning of an enzyme. They can be permanently bound to the active site or may bind loosely and reversibly along with the substrate during catalysis

chemical energy

energy available in molecules for release in a chemical reaction; a form of potential energy

energy coupling

in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction

activation energy

the amount of energy that reactants must absorb before a chemical reaction will start

reduction

the complete or partial addition of electrons to a substance involved in a redox reaction

oxidation

the complete or partial loss of electrons from a substance involved in a redox reaction

oxidizing agent

the electron acceptor in a redox reaction

reducing agent

the electron donor in a redox reaction

kinetic energy

the energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter

acetyl CoA

the entry compound for the citric acid cycle in cellular respiration formed from a fragment of pyruvate attached to a coenzyme

first law of thermodynamics

the principle of conservation of energy: energy can be transferred and transformed but it cannot be created or destroyed

substrate

the reactant on which an enzyme works

active side

the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs

thermodynamics

the study of energy transformations that occur in a collection of matter

thermal energy

the total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter

metabolism

the totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism