Metabolic Pathways, ATP, and Mitochondria Vocabulary

Vocabulary flashcards covering cellular metabolism, ATP dynamics, bioenergetics, and mitochondrial structure and function based on Becker's World of the Cell.

Chemotrophs

Organisms that obtain their required energy from the chemical breakdown of food molecules that they engulf or ingest.

Metabolism

The totality of all chemical reactions occurring within a cell, organized into specific metabolic pathways.

Anabolic Pathways

Endergonic metabolic pathways that synthesize complex cellular components from simpler precursors, accompanied by an increase in molecular order and a decrease in entropy.

Catabolic Pathways

Exergonic metabolic pathways involved in the degradation of cellular constituents, accompanied by a decrease in molecular order, an increase in entropy, and the release of free energy.

Metabolites

Small organic building blocks produced during the catabolic degradation of larger cellular molecules.

Adenosine Triphosphate (ATP)

The primary energy currency of biological cells, comprising the aromatic base adenine, a five-carbon ribose sugar, and three phosphate groups linked by phosphoanhydride and phosphoester bonds.

Charge Repulsion

The electrostatic repulsion between adjacent negatively charged phosphate groups in an ATP molecule, which strains the covalent bonds linking them.

Resonance Stabilization

A thermodynamic state of lower energy resulting from the delocalization of electrons across chemical bonds, which is reduced when phosphate or carboxylate groups form ester or anhydride bonds.

Chemotrophic Energy Metabolism

The set of metabolic reactions and pathways by which cells catabolize nutrients and conserve the released energy in the form of ATP.

Dehydrogenation

A biological oxidation reaction that involves the removal of both an electron and a proton (a hydrogen atom) from an organic substrate.

Dehydrogenases

Enzymes that catalyze biological oxidation reactions by transferring hydrogen atoms from a donor substrate to an electron acceptor.

Hydrogenation

A reduction reaction in biological systems where the addition of electrons is accompanied by the addition of protons.

Coenzymes

Small organic molecules that function alongside enzymes as recyclable carriers of electrons or functional groups.

Nicotinamide Adenine Dinucleotide (NAD+)

An essential coenzyme that serves as an electron acceptor in cellular energy metabolism, adding two electrons and one proton to its aromatic ring to yield reduced NADH.

Aerobic Respiration

The complete oxidation of organic substrates such as glucose to carbon dioxide and water in the presence of molecular oxygen as the terminal electron acceptor.

Fermentation

An anaerobic metabolic process in which electrons removed during glucose oxidation are transferred back to an organic metabolite later in the pathway, yielding limited ATP.

Obligate Aerobes

Organisms that have an absolute requirement for molecular oxygen to perform cellular respiration and survive.

Obligate Anaerobes

Organisms that cannot use molecular oxygen as an electron acceptor because oxygen is toxic to them.

Facultative Organisms

Organisms that can function and generate energy under either aerobic or anaerobic conditions.

Cellular Respiration

The flow of electrons through or within a membrane from reduced coenzymes to an external electron acceptor, coupled with the synthesis of ATP.

Mitochondrial Structure

The double-membrane organization of the eukaryotic energy powerhouse, consisting of an outer membrane, an intermembrane space, an inner boundary membrane with cristae infoldings, and an interior matrix.

Porins

Transmembrane channel proteins located in the outer mitochondrial membrane that allow passage of solutes with molecular weights up to $5000\,\text{Da}$.

Mitochondrial Matrix

The semifluid interior compartment of a mitochondrion containing metabolic enzymes for pyruvate oxidation and the citric acid cycle, circular mtDNA, and ribosomes.

Cristae

Infoldings of the inner mitochondrial membrane that expand its surface area for electron transport and accommodate localized intracristal spaces for proton accumulation.

Crista Junctions

Small passageways or narrow openings that connect the cristae membranes to the inner boundary membrane of the mitochondrion.

Transit Sequence

An N-terminal targeting signal on a newly synthesized polypeptide that directs its import into the mitochondrion.

Transit Peptidase

A mitochondrial matrix enzyme that cleaves the N-terminal transit sequence from an imported polypeptide once it enters the matrix.

TOM and TIM Import Complexes

Translocase of the Outer Membrane (TOM) and Translocase of the Inner Membrane (TIM); protein complexes that cooperate with chaperone proteins to translocate unfolded polypeptides across mitochondrial membranes.

FoF1 ATP Synthase Complex

A multi-subunit enzyme complex in the inner mitochondrial membrane where the membrane-embedded Fo complex conducts protons and the matrix-facing F1 complex catalyzes ATP synthesis.

F1 Complex

The catalytic knoblike structure of ATP synthase that projects into the mitochondrial matrix and synthesizes ATP from ADP and inorganic phosphate.

Fo Complex

The oligomycin-sensitive hydrophobic protein complex embedded in the inner mitochondrial membrane that serves as a proton channel driving ATP synthesis.