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