Cellular Respiration and Enzyme Function

Vocabulary flashcards covering cellular metabolism, enzyme structures, glycolysis, the Krebs cycle, electron transport, and chemiosmosis based on the lecture transcript.

Catabolism

The metabolic process of breaking down large molecules into smaller molecules, such as degrading carbohydrates into glucose or proteins into amino acids.

Anabolism

The metabolic process of rebuilding small molecules into macromolecules required by the cell or body.

Oxidation

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

Reduction

The gain of one or more electrons by a chemical molecule or atom during a metabolic reaction.

Active Site

The specific three-dimensional location on an enzyme where the substrate binds precisely, similar to a piece in a jigsaw puzzle.

Substrate

The starting chemical molecule that binds to the active site of an enzyme to undergo a chemical transformation.

Product

The resulting molecule or molecules formed and released after an enzyme acts upon its substrate.

Coenzyme

A non-protein organic molecule, such as a B vitamin (niacin, vitamin $B_1$, biotin, or pantothenic acid), that makes up roughly $1\%$ or less of an enzyme and is essential for its catalytic activity.

Cofactor

An inorganic metal ion, such as iron, magnesium, cobalt, or zinc, attached to an enzyme that is required for proper enzyme function.

Oxidoreductase

A class of enzymes that catalyzes oxidation-reduction reactions by transferring electrons between molecules.

Cellular Respiration

The multi-step process taking place inside cells where glucose is broken down in the presence of oxygen across three stages: glycolysis, synthesis of acetyl CoA and the Krebs cycle, and the electron transport chain.

Glycolysis

Also called the Embden-Meyerhof pathway, a 10-step series of reactions mediated by 10 different enzymes that splits one 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules, yielding net $2\text{ ATP}$, $2\text{ NADH}$, and $2\text{ protons}$.

Pyruvic Acid

A 3-carbon compound produced at the end of glycolysis from the splitting of glucose.

Phosphoketolase Pathway

An alternative metabolic pathway to glycolysis used by certain bacteria, such as Bifidobacterium found in yogurt, to break down glucose.

Entner-Doudoroff Pathway

An alternative glucose breakdown pathway utilized by bacteria like Pseudomonas and Rhizobium rather than the standard glycolytic pathway.

Acetyl CoA

A 2-carbon molecule formed when a 3-carbon pyruvic acid loses one carbon as carbon dioxide during the preparatory step before entering the Krebs cycle.

Krebs Cycle

An 8-step metabolic cycle occurring in the mitochondria of humans where the two carbons of acetyl CoA are fully released as carbon dioxide, while electrons and protons are transferred to carrier molecules.

Electron Transport Chain

A sequence of membrane-associated proteins—including FMN, coenzyme Q, and cytochromes b, c1, c, a, and a3—that sequentially pass energetic electrons ultimately to oxygen.

Periplasmic Space

The narrow region between the cell wall and plasma membrane in bacteria where protons accumulate during electron transport to establish high pressure and an electrochemical gradient.

ATP Synthase

A channel-containing enzyme that utilizes the flow and pressure of protons rushing from the periplasm or intermembrane space into the cytoplasm to synthesize ATP from ADP and inorganic phosphate.

Chemiosmosis

The biological process in which the movement of electrons and protons across a biological membrane is directly coupled to the synthesis of ATP by ATP synthase.

Metabolic Water

Water formed inside the cell when protons rushing back into the cytoplasm rejoin electrons and bind with inhaled oxygen at the conclusion of the electron transport chain.