AP Bio - Unit 3: Cell Energetics

First Law of Thermodynamics

Energy is neither created nor destroyed, just transformed

Second Law of Thermodynamics

Entropy is always increasing in a closed system

Entropy Increasing

Negative Delta G, spontaneous, energy-releasing reactions, catabolic reaction, exergonic reaction, hydrolysis

Catabolic Reaction

“Breaking Down” Reaction

Anabolic Reaction

“Building Up” Reaction

Entropy Decreasing

Positive Delta G, non-spontaneous, energy-storing reactions, anabolic reaction, endergonic reaction

Substrate

Reactant an enzyme acts on, attaches with H-bonds

Active Site

Region on enzyme where substrate binds by induced fit (___ of enzyme conforms itself to substrate)

Cofactors

Small, inorganic, ions, minerals (ex. Ca+2)

Coenzymes

Large, organic, vitamins (ex. NAD+)

Competitive Inhibition

Inhibitor molecule competes with substrate for same active site on enzyme

• Inhibitor mimics substrate and blocks active site

• Molecule with higher concentration “wins” active site

Noncompetitive Inhibition

Inhibitor molecule binds to allosteric effector site

• When molecule binds to effector site, active site is deformed; changes function

Negative Feedback/Feedback Inhibition

Initial substrate produces product which binds to initial substrate’s effector site; block initial reaction from occurring