Energy, Enzymes, and Metabolism Lecture Flashcards

A set of vocabulary flashcards covering the key concepts of metabolism, thermodynamics, and enzyme kinetics based on the lecture material.

Chemical Reaction

Occurs when atoms have enough energy to combine or change bonding partners.

Metabolism

The sum total of all chemical reactions occurring in a biological system at a given time.

Energy

The capacity to do work, or the capacity for change.

Potential Energy

Energy stored as chemical bonds, concentration gradient, or charge imbalance.

Kinetic Energy

The energy of movement.

Anabolic Reactions

Metabolic reactions where complex molecules are made from simple molecules and energy is required.

Catabolic Reactions

Metabolic reactions where complex molecules are broken down to simpler ones and energy is released.

First Law of Thermodynamics

Energy cannot be created or destroyed, only converted from one form to another.

Second Law of Thermodynamics

States that during energy conversions, much escapes as heat and energy flows from concentrated to less concentrated forms.

Entropy (S)

A measure of the disorder in a system; it takes energy to impose order.

Enthalpy (H)

The total energy in a biological system.

Free Energy (G)

The usable energy that can do work.

Exergonic Reaction

A reaction that releases free energy, where $\text{ΔG}$ is negative ($\text{ΔG} < 0$).

Endergonic Reaction

A reaction that requires energy, where reactants are converted to products with a higher energy level and $\text{ΔG}$ is positive ($\text{ΔG} > 0$).

Chemical Equilibrium

A balance between forward and reverse reactions, resulting in a state of no net change.

ATP (Adenosine Triphosphate)

A molecule that captures and transfers free energy and can phosphorylate other molecules.

Activation Energy ($E_a$)

The amount of energy required to start a reaction by putting reactants into the transition state.

Transition State

A reactive mode that reactants enter once they have enough activation energy.

Enzymes

Highly specific biological catalysts (usually proteins) that increase reaction rates by lowering the activation energy barrier.

Substrates

The reactant molecules that bind to the active site of an enzyme.

Active Site

The specific 3D location on an enzyme where substrates bind.

Induced Fit

The process where some enzymes change shape when binding a substrate, altering the shape of the active site.

Turnover Number

The number of molecules of substrate converted to product per unit time when an enzyme is at saturation.

Irreversible Inhibition

Occurs when an inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme.

Competitive Inhibitor

A molecule that competes with the natural substrate for binding sites; the degree of inhibition depends on the concentrations of substrate and inhibitor.

Uncompetitive Inhibitor

A molecule that binds to the enzyme–substrate complex, preventing the release of products.

Noncompetitive Inhibitor

A molecule that binds to the enzyme at a site other than the active site, changing the enzyme shape and altering the active site.

Allosteric Regulation

Regulation occurring when a non-substrate molecule binds to a site different from the active site, changing the enzyme's shape to an active or inactive form.