BB ch 13

A set of 200 English vocabulary flashcards covering essential terms from the Chapter 13 lecture on bioenergetics and metabolism.

Bioenergetics

The study of energy transductions in living systems and the accompanying changes in free energy.

Metabolism

The sum total of all chemical reactions occurring in a cell or organism.

Catabolism

Metabolic pathways that break down molecules and release energy.

Anabolism

Metabolic pathways that build complex molecules and require energy.

Standard Free Energy Change (ΔG°′)

The free-energy difference of a reaction under standard biochemical conditions (1 M reactants/products, pH 7, 25 °C).

Actual Free Energy Change (ΔG)

The free-energy change of a reaction at the prevailing cellular concentrations of reactants and products.

Metabolic Pathway

A linked series of enzyme-catalyzed reactions that leads from a specific substrate to a final product.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Every energy transformation increases the entropy of the universe.

Entropy

A measure of disorder; increasing entropy is favored in spontaneous processes.

Free Energy Coupling

Driving an endergonic reaction by linking it to an exergonic reaction through a shared intermediate.

Exergonic Reaction

A reaction that releases free energy (ΔG < 0).

Endergonic Reaction

A reaction that consumes free energy (ΔG > 0).

Additivity of ΔG°′

The overall standard free energy change equals the sum of individual reaction ΔG°′ values.

Hydrolysis

Cleavage of a chemical bond by the addition of water.

Acid Anhydride

A compound formed from two acids by removal of water; hydrolysis is strongly exergonic.

Acetic Anhydride

An acid anhydride whose hydrolysis yields two acetate ions and large negative ΔG°′.

Adenosine Triphosphate (ATP)

The universal energy currency containing two phosphoanhydride bonds with high free-energy of hydrolysis.

Adenosine Diphosphate (ADP)

Product of ATP hydrolysis; can accept a phosphoryl group to regenerate ATP.

Pyrophosphate (PPi)

Inorganic diphosphate released in many biosynthetic reactions; its hydrolysis drives unfavorable steps.

Nicotinamide Adenine Dinucleotide (NAD⁺)

A pyridine nucleotide coenzyme that carries two electrons and one proton in redox reactions.

Nicotinamide Adenine Dinucleotide Phosphate (NADP⁺)

Phosphorylated form of NAD⁺ used mainly in biosynthetic (reducing) pathways.

Flavin Adenine Dinucleotide (FAD)

A flavin nucleotide coenzyme capable of accepting one or two electrons.

Flavin Mononucleotide (FMN)

A flavin nucleotide coenzyme (without adenine) participating in redox processes.

Oxidation–Reduction (Redox) Reaction

A chemical process involving electron transfer between reactants.

Dehydrogenase

An enzyme that catalyzes oxidation by removing a pair of hydrogen atoms.

Phosphoryl Group Transfer

Movement of a phosphoryl group (–PO₃²⁻) from one molecule to another, often mediated by ATP.

Thioester

A compound with a sulfur atom replacing the single-bond oxygen in an ester; hydrolysis is energetically favorable.

Acetyl-CoA

A central thioester metabolite that donates acetyl groups in many pathways.

Phosphoenolpyruvate (PEP)

A high-energy phosphate compound whose hydrolysis yields the largest ΔG°′ among biological phosphates.

1,3-Bisphosphoglycerate (1,3-BPG)

A glycolytic intermediate with high phosphoryl transfer potential.

Phosphocreatine

A phosphagen that buffers ATP levels in muscle through reversible phosphoryl transfer.

Rossmann Fold

A common protein motif that binds NAD⁺/NADP⁺ coenzymes.

Pellagra

Disease caused by niacin deficiency, characterized by dermatitis, diarrhea, and dementia.

Niacin (Vitamin B3)

Vitamin precursor of the nicotinamide moiety in NAD⁺ and NADP⁺.

Tryptophan

An amino acid that can be converted to niacin in animals.

Boltzmann Constant (k)

Physical constant relating energy to temperature at the molecular scale (1.381×10⁻²³ J/K).

Avogadro's Number (N)

Number of molecules in one mole, 6.022×10²³ mol⁻¹.

Faraday Constant (F)

Charge per mole of electrons, 96,480 C mol⁻¹ (≈ J V⁻¹ mol⁻¹).

Gas Constant (R)

Proportionality constant in thermodynamics, 8.315 J mol⁻¹ K⁻¹.

Adenylate Kinase

Enzyme catalyzing 2 ADP ⇌ ATP + AMP, balancing adenine nucleotides.

Nucleoside Diphosphate Kinase

Enzyme that transfers the terminal phosphate from ATP to any NDP, forming NTP.

Creatine Kinase

Enzyme interconverting ATP and phosphocreatine to buffer muscle energy.

Polyphosphate (PolyP)

Linear chains of many phosphate residues that can act as a phosphate reservoir.

Lactate Dehydrogenase

Enzyme converting pyruvate to lactate while reoxidizing NADH.

Isocitrate Dehydrogenase

Citric-acid-cycle enzyme oxidizing isocitrate to α-ketoglutarate with NAD⁺ reduction.

α-Ketoglutarate Dehydrogenase

Multienzyme complex converting α-ketoglutarate to succinyl-CoA with NADH formation.

Malate Dehydrogenase

Enzyme oxidizing malate to oxaloacetate with NAD⁺ reduction.

Glucose 6-Phosphate Dehydrogenase

Pentose-phosphate-pathway enzyme producing NADPH from NADP⁺.

Glyceraldehyde 3-Phosphate Dehydrogenase

Glycolytic enzyme that forms 1,3-BPG while reducing NAD⁺.

Alcohol Dehydrogenase

Enzyme reducing acetaldehyde to ethanol, using NADH in fermentation.

Acyl-CoA Dehydrogenase

FAD-dependent enzyme initiating each round of fatty acid β-oxidation.

Dihydrolipoyl Dehydrogenase

FAD-containing subunit of several oxidative decarboxylation complexes.

Succinate Dehydrogenase

FAD-linked enzyme converting succinate to fumarate in the TCA cycle and electron transport chain.

Glycerol 3-Phosphate Dehydrogenase

FAD-dependent mitochondrial enzyme linking cytosolic NADH to the respiratory chain.

Thioredoxin Reductase

FAD-containing enzyme that reduces thioredoxin for redox regulation.

NADH Dehydrogenase (Complex I)

First complex of the respiratory chain that oxidizes NADH and pumps protons.

Glycolate Oxidase

FMN-dependent enzyme oxidizing glycolate to glyoxylate.

Prenyl Transferase

Enzyme forming C–C bonds by ionization of allylic pyrophosphates (e.g., terpene biosynthesis).

Nucleophile

Electron-rich species that donates an electron pair to form a bond.

Electrophile

Electron-deficient species that accepts an electron pair during bond formation.

Carbanion

Carbon species bearing a negative charge and acting as a nucleophile.

Carbocation

Positively charged carbon intermediate acting as an electrophile.

Free Radical

Molecule with an unpaired electron, highly reactive.

Homolytic Cleavage

Bond breakage yielding two radicals by equal splitting of electrons.

Heterolytic Cleavage

Bond breakage in which both electrons remain with one fragment, forming ions.

Carbonyl Group

Chemical group with a carbon double-bonded to oxygen; highly reactive in metabolism.

Enediol Intermediate

Transient double-bonded species formed during sugar isomerizations.

Isomerization Reaction

Conversion of one isomer into another, often via proton transfer within the molecule.

Aldolase Reaction

Glycolytic step that cleaves fructose 1,6-bisphosphate into two triose phosphates.

Citrate Synthesis

Condensation of acetyl-CoA with oxaloacetate to form citrate in the TCA cycle.

Fatty Acid Oxidation

Sequence of reactions that break fatty acids into acetyl-CoA units, producing NADH and FADH₂.

Dimethylallyl Pyrophosphate

Allylic isoprenoid donor in terpenoid biosynthesis.

Isopentenyl Pyrophosphate

Five-carbon isoprene unit used in prenyl chain elongation.

Geranyl Pyrophosphate

Ten-carbon precursor for monoterpene synthesis.

Lactate

Three-carbon acid produced from pyruvate under anaerobic conditions.

Pyruvate

End product of glycolysis; substrate for aerobic oxidation or fermentation.

Oxidation State of Carbon

Formal measure of electron ownership by carbon in a molecule.

Phosphoryl Transfer Potential

Relative tendency of a phosphate compound to donate its phosphoryl group.

Charge Repulsion Relief

Energy released when adjacent negative charges separate during ATP hydrolysis.

Resonance Stabilization

Delocalization of electrons that lowers free energy of hydrolysis products.

Mg²⁺ Coordination with ATP

Binding of magnesium ions to ATP, shielding negative charges and orienting phosphates.

Phosphoanhydride Bond

High-energy bond between two phosphate groups in ATP.

Phosphate Ester

Bond between phosphate and an alcohol group (e.g., glucose 6-phosphate).

High-Energy Phosphate Compound

Molecule whose hydrolysis releases large free energy (e.g., PEP, ATP).

Transphosphorylation

Interconversion of nucleoside triphosphates via phosphate transfer.

Adenylyl Transfer

Transfer of AMP moiety from ATP to a substrate.

Pyrophosphoryl Transfer

Transfer of βγ-pyrophosphate group from ATP.

Phosphoryl Transfer

Transfer of a single phosphate from ATP’s γ-position.

Luciferase

Enzyme in firefly bioluminescence that emits light proportional to ATP.

Luciferin

Substrate oxidized by luciferase to produce light.

Firefly Bioluminescence Assay

Sensitive method for quantifying picomole levels of ATP using light emission.

Phosphocreatine Shuttle

System that rapidly regenerates ATP from ADP in muscle via creatine kinase.

ATP/ADP Ratio

Indicator of cellular energy status; normally kept high in living cells.

Heme Biosynthesis

Metabolic pathway producing heme, involving radical decarboxylation steps.

Coproporphyrinogen III

Intermediate in the heme biosynthetic pathway.

Protoporphyrinogen IX

Late intermediate in heme synthesis, converted to protoporphyrin IX.

Semiquinone

One-electron-reduced form of flavin (FADH• or FMNH•).

FMNH₂

Fully reduced form of FMN after accepting two electrons and two protons.

FADH₂

Fully reduced form of FAD used to transfer electrons to the respiratory chain.