Metabolic Pathways, Energetics, Redox Reactions, and Cellular Recycling

Vocabulary flashcards covering metabolic pathways, catabolism vs. anabolism, ATP energy changes, redox reactions, pathway regulation, and organelle/protein recycling processes.

Metabolic Pathway

A multi-step biological process involving sequential enzymatic reactions where an initial substrate is converted through intermediates to produce a specific final product.

Catabolic Reaction

A metabolic reaction that breaks down larger molecules into smaller ones, releasing energy (exergonic, spontaneous, negative delta G) and supplying energy to synthesize ATP.

Anabolic Reaction

A metabolic reaction that builds larger molecules from smaller monomers, requiring energy input (endergonic, non-spontaneous) often supplied by ATP hydrolysis.

ATP Hydrolysis Energy Yield

The cleavage of ATP into ADP and inorganic phosphate ($P_i$), which releases $7.3\,\text{kcal/mol}$ of free energy with a negative delta G.

Oxidation

The removal or loss of one or more electrons from an atom or molecule during a chemical reaction.

Reduction

The addition or gain of one or more electrons by an atom or molecule, which decreases its net charge and increases its stored energy.

Redox Reaction

A coupled chemical reaction combining an oxidation step (electron loss) and a reduction step (electron gain).

Reducing Agent

The reactant in a redox reaction that donates electrons to another compound, becoming oxidized in the process.

Oxidizing Agent

The reactant in a redox reaction that accepts electrons from another compound, becoming reduced in the process.

OIL RIG

A study mnemonic for redox reactions standing for Oxidation Is Losing, Reduction Is Gaining electrons.

LEO says GER

A study mnemonic for redox reactions standing for Lose Electrons Oxidation, Gain Electrons Reduction.

Gene Regulation

A pathway regulation mechanism that turns specific genes on or off to increase or decrease transcription and translation of metabolic enzymes based on environmental conditions.

Cellular Regulation

A metabolic control mechanism where external cell signals, such as hormones like epinephrine, signal the cell to adapt pathways like carbohydrate metabolism to current physiological demands.

Biochemical Regulation

Direct regulation of metabolic pathways via non-covalent binding of regulatory molecules (activators or inhibitors) directly to enzymes to alter reaction rates.

Competitive Inhibitor

A regulatory molecule that directly competes with a substrate to bind at an enzyme's active site.

Noncompetitive Inhibitor

A regulatory molecule that binds to an enzyme's allosteric site rather than the active site, altering the enzyme's 3D structure and preventing proper catalytic function.

Feedback Inhibition

A pathway regulation method where excess accumulation of a final metabolic product acts as an inhibitor on an early enzyme in the pathway to conserve cellular resources.

Rate-Limiting Step

The slowest step in a multi-step metabolic pathway, which possesses the highest activation energy and serves as a major site for cellular regulation.

Half-Life

The time required for half of a specific cellular component or macromolecule (such as proteins or RNA, excluding DNA) to break down.

Protease

An enzyme that hydrolyzes the peptide bonds connecting amino acids within proteins to recycle them into individual amino acid building blocks.

Autophagy

The cellular recycling process in which an entire degraded or old organelle is enclosed in a double membrane and degraded by acid hydrolases upon fusion with a lysosome.

Autophagosome

A double-membrane vesicle formed during autophagy that encapsulates a target organelle before fusing with a lysosome for breakdown.