Energy, Metabolism, and Enzyme Function in Cells

Enzyme

Biological catalysts that facilitate chemical reactions.

Active Site

Enzyme's catalytic site; substrate fits into active site.

Substrate

Reactant which binds to enzyme.

Product

End result of reaction.

Denaturation

Occurs when the protein structure is disrupted, eliminating the ability to catalyze reactions.

Activation Energy (Eₐ)

Initial energy investment required to break stable covalent bonds.

Endergonic Reaction

Reactions that require energy input (+).

Exergonic Reaction

Reactions that release energy (-).

Hydrolysis

A catabolic process that breaks down molecules.

Dehydration Synthesis

An anabolic process that builds biomolecules.

pH

A measure of hydrogen ion concentration, calculated as pH = -log [H+].

Competitive Inhibitor

Molecules that can bind reversibly or irreversibly to the active site of the enzyme.

Noncompetitive Inhibitor

Molecules that can bind allosteric sites, changing the activity of the enzyme.

Enzyme-Substrate Complex

Temporary association between an enzyme and its substrate.

Induced Fit Model

More accurate model of enzyme action where substrate binding causes enzyme to change shape.

Lock & Key Model

Simplistic model of enzyme action where substrate fits into the enzyme's active site.

Metabolism

The general term for all of the chemical processes that occur in the body.

Catabolic Pathways

Metabolic pathways that break down molecules.

Anabolic Pathways

Metabolic pathways that build up molecules.

Environmental Factors

Conditions such as temperature, pH, and salinity that affect enzyme activity.

Enzyme Naming

Enzymes are named for the reaction they catalyze.

Reaction Specificity

Each enzyme works with a specific substrate.

Chemical Fit

The interaction between the active site and substrate through hydrogen and ionic bonds.

Conformational Change

The change in shape of an enzyme upon substrate binding.

Energy Coupling

Using exergonic reactions to fuel endergonic reactions.

Hydrogen Bonds

Interactions that help maintain enzyme structure and can be disrupted by environmental changes.

Efficiency of Enzyme Activity

Determined by environmental pH and relative concentrations of substrates and products.

Enzyme concentration

Higher concentration increases reaction rate.

Substrate concentration

More substrate leads to more frequent collisions.

Reaction rate

Speed at which reactants convert to products.

Active site

Region where substrate binds on an enzyme.

Saturation

All enzyme active sites occupied by substrate.

Optimum temperature

Temperature for maximum enzyme activity.

Ectotherms

Organisms relying on environmental temperature.

Optimal pH

pH range for maximum enzyme activity.

Salinity

Concentration of salts affecting enzyme function.

Cofactors

Inorganic compounds aiding enzyme function.

Coenzymes

Organic molecules that assist enzyme activity.

Non-competitive inhibitors

Bind away from active site, altering shape.

Competitive inhibitors

Compete with substrate for active site binding.

Irreversible inhibition

Permanent binding of inhibitor to enzyme.

Feedback inhibition

Final product inhibits an earlier pathway step.

Metabolic pathways

Series of chemical reactions in living organisms.

Energy coupling

Linking exergonic and endergonic reactions.

Thermodynamics

Study of energy transformations in systems.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Second Law of Thermodynamics

Entropy increases in energy transformations.

Human enzyme temperature range

Optimal activity between 35°C and 40°C.

Pepsin

Enzyme active at pH 2-3 in stomach.

Trypsin

Enzyme active at pH 8 in small intestine.

Dead Sea

High salinity prevents enzyme function.

Aspirin

Irreversible inhibitor binding to active site.

Sarin

Allosteric inhibitor permanently altering enzyme shape.

Vitamin B12

Essential for red blood cell production.

Gibbs Free Energy (ΔG)

Indicates spontaneity of chemical reactions.

ΔH

Change in total energy of a system.

ΔS

Change in entropy of a system.

T

Absolute temperature in Kelvin (K).

Entropy

Measure of disorder in a system.

Photosynthesis

Process converting solar energy into organic molecules.

Kinetic Energy (KE)

Energy of motion; measured by temperature.

Potential Energy (PE)

Stored energy based on position or arrangement.

Chemical Energy

Potential energy in molecular atomic arrangements.

Calorie

Energy needed to raise 1 mL water by 1°C.

Kilocalorie

1,000 calories; energy measurement in food.

ATP

Primary energy currency of the cell.

ADP

Adenosine diphosphate; product of ATP hydrolysis.

Phosphorylation

Transfer of phosphate group to another molecule.

ATP Hydrolysis

Breakdown of ATP releasing energy for work.

Metabolic Rate

Speed of biochemical reactions in organisms.

ATP Cycle

Regeneration of ATP from ADP and Pi.

Mechanical Work

Movement-related work in cells.

Transport Work

Pumping substances across cell membranes.

Chemical Work

Synthesis of molecules from smaller units.

Entropy Tax

Energy loss due to inefficiency in transformations.

2,4-Dinitrophenol (DNP)

Weight-loss drug causing metabolic disruption.

Hyperthermia

Elevated body temperature due to metabolic issues.

Metabolic Acidosis

Condition of increased acidity in body fluids.