Module 3 - ATP & REDOX

Vocabulary flashcards covering metabolism, thermodynamics, ATP hydrolysis, energy coupling, redox reactions, electron carriers, and enzyme regulation from Chapter 8 and 9.

Metabolism

The totality of all chemical reactions that occur within an organism to transform matter and energy.

Catabolism

Metabolic pathways that release energy by breaking down complex polymers into simpler monomers (such as polysaccharides into monosaccharides or proteins into amino acids), characterized by a negative change in free energy ($\Delta G < 0$).

Anabolism

Metabolic pathways that consume energy to synthesize complex polymers from simpler monomers (such as amino acids into proteins), characterized by a positive change in free energy ($\Delta G > 0$).

Exergonic Reaction

A spontaneous chemical reaction that releases energy to its surroundings, where the products have less energy than the reactants ($\Delta G < 0$).

Endergonic Reaction

A non-spontaneous chemical reaction that absorbs energy from its surroundings, where the products have more energy than the reactants ($\Delta G > 0$).

Hydrolysis

A catabolic chemical process that breaks covalent bonds in polymers to yield smaller units through the addition of a water molecule ($H_2O$).

Dehydration Synthesis

An anabolic chemical process that covalently links monomers together into larger polymers accompanied by the removal of a water molecule ($H_2O$).

Adenosine Triphosphate (ATP)

A nucleotide containing adenine, ribose, and three phosphate groups that functions as the immediate energy source for cellular work; breaking its terminal high-energy bond releases $7.3\,\text{kcal/mol}$.

Energy Coupling

The use of an exergonic process (such as the hydrolysis of ATP) to drive an endergonic process.

Phosphorylated Intermediate

A temporary molecule that receives a phosphate group transferred from ATP (such as glutamic acid coupled with ATP), elevating its free energy so it can react with another molecule (such as ammonia to form glutamine).

Chemical Work

The pushing of endergonic reactions that would not occur spontaneously, including polymer synthesis and DNA replication.

Transport Work

The pumping of substances across cell membranes against the direction of spontaneous movement (active transport, such as the sodium-potassium pump) powered by ATP.

Mechanical Work

Cellular movement powered by ATP, including the contraction of muscle cells, the beating of cilia or flagella, and the movement of motor proteins carrying cargo along cytoskeletal fibers.

Glycolysis

The initial metabolic pathway in the cytoplasm that breaks down glucose into pyruvate/pyruvic acid, functioning independently of whether oxygen is present.

Fermentation

An anaerobic catabolic pathway involving incomplete oxidation of fuel that yields organic waste products (such as lactate or alcohol) and a net gain of $2\,\text{ATP}$.

Cellular Respiration

A controlled, complete oxidation catabolic pathway that breaks down organic fuels with oxygen or another terminal electron acceptor, yielding inorganic waste ($CO_2$ and $H_2O$) and a net of $36\,\text{ATP}$.

Oxidation

The loss of electrons from a substance during a redox reaction (often tracked by the loss of hydrogen atoms).

Reduction

The addition or gain of electrons to a substance during a redox reaction (often tracked by the gain of hydrogen atoms).

Reducing Agent

The electron donor in a redox reaction, which becomes oxidized in the process.

Oxidizing Agent

The electron acceptor in a redox reaction, which becomes reduced in the process.

$NAD^+$ / $NADH$

A coenzyme electron carrier where $NAD^+$ is the oxidized state and $NADH$ is the reduced state formed upon accepting $2\,\text{electrons}$ and $1\,\text{proton}$ ($H^+$).

$FAD$ / $FADH_2$

A coenzyme electron carrier where $FAD$ is the oxidized state and $FADH_2$ is the reduced state formed when double bonds between nitrogen and carbon break to accept $2\,\text{electrons}$ and $2\,\text{protons}$ ($2H^+$).

Electron Affinity

The attraction of a molecule for free electrons; in the electron transport chain, molecules are arranged in sequence from low to high affinity, terminating at oxygen which has the greatest affinity.

Cristae

Folds of the inner mitochondrial membrane across which the electron transport chain and ATP synthesis occur.

Substrate-Level Phosphorylation

The direct enzymatic transfer of a phosphate group from an organic substrate molecule to ADP to generate ATP, as seen in glycolysis and the Krebs cycle.

Oxidative Phosphorylation

The mode of ATP synthesis powered by redox reactions transferring electrons through an electron transport chain to oxygen, coupled with chemiosmosis.

Metabolic Water

Water formed intracellularly as a byproduct of the reduction of oxygen during cellular respiration (e.g., providing desert kangaroo rats with $54\,\text{g}$ out of $60\,\text{g}$ of their total water gain).

Active Site

The specific region of an enzyme that binds the substrate and where catalysis occurs.

Allosteric Regulation

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

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.

Cooperativity

A type of allosteric regulation where the binding of a substrate molecule to one active site in a multisubunit enzyme stabilizes favorable conformational changes in all other subunits.

Chemical Equilibrium in Living Systems

A state where forward and reverse reaction rates are balanced resulting in $\Delta G = 0$; because systems at equilibrium can perform no work, chemical equilibrium in a biological system equates to death.