Bioenergetics and Enzymes

Vocabulary flashcards covering core bioenergetics concepts, metabolic processes, thermodynamics, and enzyme functions based on the lecture notes.

Exergonic reaction

A reaction where the products have less free energy than the reactants; free energy is released to the surroundings.

Endergonic reaction

A reaction where the products have more free energy than the reactants; energy is absorbed from the surroundings.

Exothermic / Endothermic

Terms referring specifically to heat release or absorption; distinct from exergonic/endergonic which refer to free energy.

Metabolism

The sum of all anabolic (building) and catabolic (breaking down) reactions in an organism.

Anabolic reaction

Biosynthetic process that builds larger, more complex molecules from smaller ones; typically endergonic and often involves dehydration synthesis.

Catabolic reaction

Breakdown of large molecules into smaller units; typically exergonic and often involves hydrolysis.

Hydrolysis

Reaction in which water is used to break bonds (e.g., splitting a disaccharide into monosaccharides).

Dehydration synthesis (condensation)

Reaction that forms bonds between subunits with the removal of water.

Activation energy ($E_a$)

The initial energy input required to start a chemical reaction (to reach the transition state); even exergonic reactions require $E_a$.

Catalyst

A substance that speeds up a reaction without being consumed; enzymes are biological catalysts.

Enzyme

A protein catalyst that lowers activation energy and increases reaction rate; has specificity for substrates via an active site.

Substrate

The reactant molecule(s) that bind to an enzyme's active site.

Active site

The specific region of an enzyme where substrates bind and the reaction is catalyzed.

Denaturation

Loss of a protein's native structure (and function) due to factors like temperature or pH change.

ATP (adenosine triphosphate)

Cellular energy currency; three phosphate groups in series with negative charges create high potential energy in the phosphate bonds.

Metabolic pathway

A series of linked enzyme-catalyzed reactions leading to a specific product or breakdown.

Entropy

A measure of disorder; the second law of thermodynamics states that entropy of the universe tends to increase.

Coupling (reaction coupling)

Using the energy released by an exergonic reaction to drive an endergonic reaction (often via ATP or enzyme-mediated mechanisms).