BIO EXAM 3: ENZYMES

Endergonic reaction

One that results in an increase in free energy; another way of referring to a nonspontaneous reaction.

Exergonic Reaction

One that results in a decrease in free energy; another way of referring to a spontaneous reaction.

Activation energy

The amount of energy required to get a chemical reaction through its transition state.

Transition state

During a chemical reaction, an intermediate state where old bonds are being broken but new bonds have not yet formed.

Enzyme

A protein that catalyzes a chemical reaction.

Active site

The place on an enzyme (or ribozyme) where a reaction is catalyzed.

Endergonic reaction

A chemical reaction that results in an increase in free energy; it is nonspontaneous and requires energy input.

Exergonic reaction

A chemical reaction that results in a decrease in free energy; it is spontaneous and releases energy.

Energetic coupling

A cellular process that can make required chemical reactions spontaneous, though it does not necessarily make them fast.

Spatial orientation

The precise geometric alignment required when reactants collide in order for old bonds to break, new bonds to form, and electrons and nuclei to interact.

Transition state

An unstable intermediate condition occurring as old chemical bonds break and before new bonds form, characterized by a spike in free energy.

Activation energy

The magnitude of the free energy spike that reacting substances must overcome to reach the unstable transition state.

Catalyst

An agent that accelerates the rate of a chemical reaction without being consumed or structurally altered by the reaction.

Enzymes

Proteins that act as catalysts by aligning reactants in the correct spatial orientation and lowering activation energy without altering the free energy of reactants or products.

Active site

A specific region of an enzyme where reactants bind to R-groups, bringing them into proper spatial orientation and stabilizing the transition state.

Enzyme specificity

The characteristic of an enzyme to catalyze only one particular reaction due to the unique size, shape, and chemical composition of its active site.

Electrical energy

Energy related to the movement of charged particles, such as electrons moving through wires or ions flowing across membranes down concentration and charge gradients.

Thermal energy

The energy of motion in ions and molecules, measured as temperature, where an increase in temperature signifies faster molecular movement.

Potential energy

Energy related to position; in biology, a key form is based on the position of electrons in chemical bonds relative to atomic nuclei.

Free energy

The total energy in a reaction system that is available to do work, consisting of a combination of entropy and the thermal and potential energy of the particles.

Entropy

The degree of disorder in a system; an increase in entropy from reactants to products favors a spontaneous reaction.

Spontaneous reaction

A chemical reaction that occurs without an input of energy, occurring when the products have lower free energy than the reactants.

Nonspontaneous reaction

A chemical reaction that cannot happen on its own and only occurs when energy is added to the system.

Reaction system

The specific interacting components in a chemical process, consisting of the reactants and products.

Carbonic acid ($H_2CO_3$)

A compound formed when carbon dioxide reacts with water ($CO_2 + H_2O \rightleftharpoons H_2CO_3$), which then dissociates into a proton and a bicarbonate ion ($H^+ + HCO_3^-$).

Ocean acidification

The decrease in seawater pH caused by increasing atmospheric $CO_2$ levels driving the production of carbonic acid and measurably higher concentrations of $H^+$ in the oceans.

Adenosine triphosphate (ATP)

The primary chemical energy carrier for cells, composed of three phosphate groups containing four closely packed negative charges attached to the 5-carbon sugar ribose and the nitrogenous base adenine.

Phosphorylation

The addition of a phosphate group to a protein or molecule, which can alter protein conformation to produce movement or increase the molecule's potential energy.

Energetic coupling

The cellular strategy of using high-energy reactants, such as ATP via phosphorylation, to provide the necessary energy input to make nonspontaneous reactions spontaneous.