bio uni 3

Enzyme

A protein that functions as a biological catalyst, speeding up chemical reactions by lowering activation energy.

Substrate

The reactant molecule that binds to an enzyme and is acted upon during an enzyme-catalyzed reaction.

Active Site

The specific region of an enzyme where the substrate binds and catalysis occurs; its shape and chemical properties determine substrate compatibility.

Enzyme-Substrate Complex

The temporary complex formed when a substrate binds to an enzyme's active site.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed in the reaction.

Biological Catalyst

A catalyst produced by living organisms; most biological catalysts are enzymes.

Activation Energy

The minimum energy required for reactants to reach the transition state and begin a chemical reaction.

Enzyme Specificity

The ability of an enzyme to recognize and catalyze reactions involving particular substrates due to active-site compatibility.

Induced Fit Model

The model explaining how an enzyme's active site changes shape slightly when a substrate binds, improving their interaction.

Transition State

The unstable, high-energy arrangement of atoms that reactants pass through before becoming products.

Enzyme Catalysis

The process by which an enzyme facilitates a chemical reaction by lowering its activation energy.

Cofactor

A nonprotein component, often a metal ion, required by certain enzymes to function properly.

Coenzyme

A small organic molecule that assists an enzyme during catalysis, often by transferring electrons or chemical groups.

Denaturation

The disruption of a protein's three-dimensional structure, causing it to lose its normal function.

Primary Structure

The linear sequence of amino acids in a protein, held together by peptide bonds.

Tertiary Structure

The overall three-dimensional shape of a protein formed through interactions among amino acid side chains.

Optimal Temperature

The temperature at which an enzyme catalyzes a reaction at its highest rate.

Optimal pH

The pH at which an enzyme has its greatest catalytic activity.

pH

A measure of hydrogen ion concentration that describes how acidic or basic an environment is.

Hydrogen Bonds

Weak interactions that help maintain protein structure and can be disrupted by environmental changes.

Chemical Environment

The surrounding chemical conditions, including salts, detergents, and solvents, that can affect enzyme structure and activity.

Substrate Concentration

The amount of substrate per unit volume available to interact with an enzyme.

Collision Frequency

The frequency at which enzyme and substrate molecules encounter one another.

Enzyme Saturation

The condition in which essentially all enzyme active sites are occupied, so adding more substrate no longer substantially increases reaction rate.

Maximum Reaction Rate (Vmax)

The highest rate an enzyme-catalyzed reaction can achieve when enzyme active sites are saturated with substrate.

Reaction Rate

The amount of reactant consumed or product formed per unit time.

Competitive Inhibition

Enzyme inhibition in which an inhibitor competes with the substrate for the enzyme's active site.

Competitive Inhibitor

A molecule that resembles or otherwise competes with a substrate for binding at an enzyme's active site.

Noncompetitive Inhibition

Enzyme inhibition in which an inhibitor binds at a site other than the active site and changes enzyme activity.

Noncompetitive Inhibitor

A molecule that binds away from the active site and alters enzyme activity, often by changing enzyme conformation.

Allosteric Site

A region of an enzyme separate from its active site where regulatory molecules bind.

Allosteric Regulation

The control of enzyme activity through molecules binding to an allosteric site and changing enzyme conformation.

Allosteric Activator

A regulatory molecule that binds to an allosteric site and increases enzyme activity.

Allosteric Inhibitor

A regulatory molecule that binds to an allosteric site and decreases enzyme activity.

Reversible Inhibition

Inhibition in which an inhibitor binds temporarily and enzyme activity can recover when the inhibitor dissociates.

Irreversible Inhibition

Inhibition in which an inhibitor permanently disables an enzyme, often through strong or covalent bonding.

Feedback Inhibition

A regulatory mechanism in which the final product of a metabolic pathway inhibits an enzyme involved in an earlier step.

Metabolism

The sum of all chemical reactions occurring within a cell or organism.

Metabolic Pathway

A sequence of linked chemical reactions in which the product of one reaction becomes the reactant for the next.

Catabolic Pathway

A metabolic pathway that breaks down complex molecules into simpler molecules and releases energy.

Anabolic Pathway

A metabolic pathway that builds complex molecules from simpler molecules and requires an input of energy.

Exergonic Reaction

A chemical reaction that releases free energy and has a negative change in Gibbs free energy.

Endergonic Reaction

A chemical reaction that requires an input of free energy and has a positive change in Gibbs free energy.

ATP (Adenosine Triphosphate)

The primary energy-carrying molecule in cells, composed of adenine, ribose, and three phosphate groups.

ADP (Adenosine Diphosphate)

A molecule containing adenine, ribose, and two phosphate groups; it can be converted into ATP by adding inorganic phosphate.

AMP (Adenosine Monophosphate)

A nucleotide containing adenine, ribose, and one phosphate group.

Adenine

A nitrogenous base that combines with ribose to form adenosine in ATP.

Ribose

A five-carbon sugar that forms part of the structure of ATP and other nucleotides.

Phosphate Group

A chemical group containing phosphorus and oxygen that is involved in ATP energy transfer.

Inorganic Phosphate (Pi)

A free phosphate group that can combine with ADP to form ATP.

ATP Hydrolysis

The reaction in which water breaks ATP into ADP and inorganic phosphate, releasing free energy.

ATP Synthesis

The formation of ATP from ADP and inorganic phosphate using an input of energy.

Phosphorylation

The addition of a phosphate group to a molecule, often changing its activity or reactivity.

Reactive Intermediate

A temporarily phosphorylated molecule that is more reactive and can participate in an energy-requiring reaction.

Energy Coupling

The process of linking an energy-releasing reaction, such as ATP hydrolysis, to an energy-requiring cellular reaction.

Cellular Work

Energy-requiring activities performed by cells, including chemical synthesis, transport, and movement.

Kinetic Energy

Energy associated with the motion of objects or particles.

Potential Energy

Stored energy associated with an object's position, structure, or arrangement.

Chemical Energy

Potential energy stored in the arrangement of atoms and chemical bonds within molecules.

Thermodynamics

The study of energy transformations and transfers in matter.

First Law of Thermodynamics

The principle that energy cannot be created or destroyed, only transferred or transformed.

Second Law of Thermodynamics

The principle that every energy transfer increases the total entropy of the universe.

Entropy

A measure of energy dispersal and the number of possible microscopic arrangements of a system.

Energy Coupling in Cells

The use of energy released from exergonic reactions to drive endergonic cellular processes.

Catalase

An enzyme present in cells that catalyzes the decomposition of toxic hydrogen peroxide into water and oxygen.

Hydrogen Peroxide (H2O2)

A reactive compound produced as a byproduct of cellular processes that can damage cells and is broken down by catalase.

Catalase Substrate

The hydrogen peroxide molecule (H2O2) that binds to catalase and is broken down.

Catalase Products

Water (H2O) and oxygen gas (O2), produced when catalase decomposes hydrogen peroxide.

Catalase Reaction

The balanced reaction 2H2O2 → 2H2O + O2, catalyzed by catalase.

Surface Area

The total exposed area of a material; increasing potato surface area exposes more catalase to hydrogen peroxide.

Serial Dilution

A stepwise process of reducing a solution's concentration by transferring part of it into additional solvent.

Oxygen Evolution

The release of oxygen gas as a product of hydrogen peroxide decomposition by catalase.

Foam Volume

The volume of oxygen-containing bubbles trapped by dish soap in the catalase experiment; used as an indirect measure of oxygen production.

Rate Formula (Catalase Lab)

The workbook uses r = 1/t, where t is the time in seconds for the catalase-soaked filter paper to float.

Independent Variable

The factor deliberately changed by the experimenter to determine its effect on the outcome.

Dependent Variable

The measured outcome of an experiment that responds to changes in the independent variable.

Controlled Variables

Factors kept constant throughout an experiment so that the independent variable can be evaluated fairly.

Ptyalin (Salivary Amylase)

An enzyme in saliva that breaks down starch; the workbook data show its highest activity at pH 7.

Pepsin

A protein-digesting enzyme found in the stomach; the workbook data show its highest activity at pH 2.