AP Bio Unit 3 IMPORTANT DEF

Anaerobic

A process that does not require oxygen

Aerobic

A process that requires oxygen

Energy Input

The requirement that living systems must take in more energy than they output to maintain order and offset entropy.

First Law of Thermodynamics

The principle that energy cannot be created or destroyed, only transformed (e.g., converting light or chemical energy into cellular work).

Second Law of Thermodynamics

The principle that every energy transfer increases the entropy (disorder) of the universe, meaning no energy transformation is 100% efficient.

Metabolic Pathways

Series of linked chemical reactions where the product of one reaction serves as the reactant for the next.

Energy Coupling

The process where energy released by one reaction (often exergonic) is used to power another reaction (often endergonic).

Enzyme

A protein catalyst that speeds up chemical reactions by lowering the activation energy.

Activation Energy

The minimum amount of energy required to initiate a chemical reaction.

Substrate

The specific molecule(s) that an enzyme acts upon.

Active Site

The specifically shaped region of an enzyme where the substrate binds; its charge and shape must be compatible with the substrate.

Enzyme-Substrate Complex

The temporary structure formed when a substrate is physically bound to the enzyme's active site.

Denaturation

The 'unfolding' of a protein (disruption of hydrogen bonds/secondary structure) due to extreme changes in temperature or pH, leading to a loss of function.

Optimal Range

The specific temperature or pH at which an enzyme exhibits its highest rate of catalysis.

Competitive Inhibitor

A molecule that binds directly to the active site, physically blocking the substrate from entering.

Allosteric (Non-competitive) Inhibitor

A molecule that binds to a site other than the active site, changing the enzyme's overall shape so the substrate no longer fits.

Molecular Collisions

The physical contact between enzymes and substrates required for a reaction to occur.

Substrate/Enzyme Concentration

Increasing the amount of either increases the frequency of collisions and, therefore, the reaction rate (up to a point of saturation).

Kinetic Energy (Temperature)

Increasing temperature speeds up molecular motion, increasing the likelihood and force of collisions between enzymes and substrates.

Matrix of a Cell

cytoplasm

Chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.