Enzymes, Water, Acids & Bases

Introduction

This study guide covers the foundational chemical principles essential for understanding Anatomy & Physiology. Topics include chemical bonds and energetics, reaction rates, enzyme function, water's physiological roles, acids and bases, the pH scale, and pH buffers.

Chemical Bonds and Energetics

Notation and Energetics of Chemical Bonds

Chemical bonds are the forces holding atoms together in molecules. The formation and breaking of these bonds involve energy changes that are crucial for biological processes.

• Chemical Reaction: A process where chemical bonds are broken, formed, or rearranged, and electrons may be transferred between atoms.

• Reactants: Substances that enter into a reaction.

• Products: Substances formed as a result of a reaction.

• Intermediates: Substances formed in the middle of a reaction sequence.

Energetics:

• Endergonic Reaction: Requires energy input; products have more energy than reactants. Example: Photosynthesis.

• Exergonic Reaction: Releases energy; products have less energy than reactants. Example: Cellular respiration.

General Reaction Notation:

• Reversible Reaction:

• Exchange Reaction:

Additional info: Endergonic reactions are essential for biosynthesis, while exergonic reactions provide energy for cellular activities.

Factors Influencing Reaction Rates

Key Factors

The rate of a chemical reaction is determined by several factors:

• Physical Contact: Reactants must collide.

• Overcoming Repulsion: Reactants must overcome electron repulsion.

• Concentration: Higher reactant concentration increases reaction rate.

• Temperature: Higher temperature generally increases reaction rate.

• Catalysts: Substances that lower activation energy, speeding up reactions without being consumed.

Activation Energy (): The minimum energy required for a reaction to occur.

Enzymes

Properties, Actions, and Importance

Enzymes are biological catalysts that accelerate chemical reactions in the body.

• Specificity: Each enzyme has a unique active site that binds specific substrates.

• Lower Activation Energy: Enzymes reduce the energy required for reactions.

• Reusable: Enzymes revert to their original structure after catalysis.

• Protein Nature: Most enzymes are proteins and can be denatured by heat or pH changes.

Example: Sucrase catalyzes the hydrolysis of sucrose into glucose and fructose.

Enzyme Deficiencies:

• Tay-Sachs Disease: Deficiency of hexosaminidase; leads to neural damage.

• SCIDs: Adenosine deaminase deficiency; severe immune deficiency.

• Phenylketonuria: Deficiency of phenylalanine hydroxylase; can cause neurological damage.

Factors Affecting Enzyme Activity

• Temperature: Increases reaction rate up to a point; high temperatures denature enzymes.

• Substrate Concentration: Higher substrate increases rate until saturation.

• Product Concentration: High product can slow reaction (negative feedback).

• Enzyme Concentration: More enzyme increases activity up to a limit.

• pH: Enzymes have optimal pH ranges; extreme pH denatures enzymes. Example: Pepsin works best at acidic pH in the stomach.

Water: Physiological Properties

Key Properties

Water is vital for life due to its unique chemical and physical properties.

• Heat Absorption: Absorbs heat without significant temperature change.

• Heat Transport: Carries heat when changing state (liquid to gas).

• Cushioning: Protects body structures.

• Lubrication: Reduces friction between surfaces.

• Solvent Properties: Dissolves hydrophilic (ionic and polar) substances; does not dissolve hydrophobic substances.

Hydration Sphere: Water surrounds ions, keeping them dissolved and mobile for physiological processes.

Acids, Bases, and pH

Properties of Acids and Bases

Acids and bases are substances that alter the concentration of hydrogen ions () and hydroxide ions () in solution.

• Acids: Electrolytes that ionize and dissociate in water, releasing ions (proton donors).

• Bases: Electrolytes that ionize and dissociate in water, releasing ions (proton acceptors).

Examples:

• Acid:

• Base:

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution, indicating its acidity or alkalinity.

• Definition:

• Low pH: High concentration (acidic).

• High pH: Low concentration (alkaline/basic).

• Neutral pH: Pure water has a pH of approximately 7.

pH Buffer Systems

Buffers are molecules that prevent rapid changes in pH by absorbing or releasing ions.

• Function: Maintain pH equilibrium in biological systems.

• Mechanism: Release when pH rises; bind when pH falls.

• Example: Carbonic acid-bicarbonate buffer in blood:

Additional info: Blood pH is tightly regulated; deviations can lead to acidosis or alkalosis, both of which are life-threatening.

Summary Table: Properties of Acids and Bases

pH Indicators

pH indicators are substances that change color depending on the pH of the solution, allowing for visual estimation of acidity or alkalinity. Example: pH paper, red cabbage extract.