Chapter 2 Basic Concepts

Function and Mechanism of Physiology

Physiology explores how living organisms function at molecular, cellular, and systemic levels. Understanding the chemical principles underlying physiological processes is essential for grasping how life is sustained.

• Why: To explain the mechanisms that allow cells and organisms to survive and adapt.

• How: By studying the interactions of biomolecules and the laws of chemistry and physics.

Miller’s Experiment and the Importance of Biomolecules

Miller-Urey Experiment (1953)

The Miller-Urey experiment demonstrated that organic molecules essential for life could be synthesized from inorganic precursors under conditions simulating early Earth.

• Key Finding: Formation of amino acids and other organic compounds from simple gases (e.g., H2O, CH4, NH3, H2).

• Significance: Provided evidence for chemical origins of life.

Additional info: The experiment used electrical sparks to simulate lightning, leading to the synthesis of amino acids.

Properties of Biomolecules

Complex molecules can self-assemble, replicate themselves, and act as catalysts to accelerate chemical reactions necessary for life.

• Self-assembly: Spontaneous organization of molecules into functional structures.

• Replication: Ability to make copies of themselves (e.g., DNA).

• Catalysis: Enzymes speed up reactions that would otherwise be too slow.

Essential Elements for Life

Major and Minor Essential Elements

Living organisms require specific elements for structure and function. These are classified as major and minor essential elements.

Additional info: Major elements are required in larger quantities; minor elements are needed in trace amounts but are still vital.

Catalytic Active Site Metals

Many enzymes require metal ions at their active sites to function as catalysts (e.g., Mg2+, Zn2+).

Important Ions of the Body

Cations and Anions

Definition and Classes of Biomolecules

Four Major Classes

Biomolecules are organic molecules essential for life, classified into four main groups:

• Carbohydrates: Energy storage and structural components.

• Lipids: Membrane structure, energy storage, signaling.

• Proteins: Catalysis, structure, transport, signaling.

• Nucleotides: Genetic information storage and transfer (DNA, RNA).

Additional info: Proteins are often considered the "workhorses" of the cell due to their diverse functions.

Common Functional Groups

Atomic Structure and Key Elements

Structure of the Atom

Atoms consist of a nucleus (protons and neutrons) surrounded by electrons. The arrangement of electrons determines chemical reactivity.

• Ions: Atoms or molecules with a net electric charge due to loss or gain of electrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Cations: Positively charged ions.

• Anions: Negatively charged ions.

Biological Role of Electrons

Electrons play four major roles in biology:

• Forming chemical bonds

• Participating in redox reactions

• Determining molecular shape

• Enabling electrical signaling in cells

Types of Chemical Bonds

Covalent Bonds

Covalent bonds involve the sharing of electron pairs between atoms. They can be polar (unequal sharing) or non-polar (equal sharing).

• Polar covalent bond: Water (H2O)

• Non-polar covalent bond: Methane (CH4)

Non-Covalent Bonds

Non-covalent interactions are weaker than covalent bonds but crucial for biological structure and function.

• Ionic bonds: Attraction between oppositely charged ions.

• Hydrogen bonds: Weak attraction between a hydrogen atom and an electronegative atom.

• Van der Waals forces: Weak, transient interactions due to fluctuating electron clouds.

Non-Covalent Interactions

• Hydrophilic: Molecules that interact well with water.

• Hydrophobic: Molecules that repel water.

• Molecular shape: Determines biological activity and interactions.

Solutions and Solubility

Solute, Solvent, Solution, and Solubility

Understanding the difference between these terms is essential for studying physiological processes.

• Solute: Substance dissolved in a solvent.

• Solvent: Substance that dissolves the solute (usually water in biology).

• Solution: Homogeneous mixture of solute and solvent.

• Solubility: Ability of a substance to dissolve in a solvent.

Acids, Bases, and pH

Definition of pH, Acids, and Bases

pH measures the concentration of hydrogen ions (H+) in a solution.

• Acid: Molecule that increases H+ concentration in solution.

• Base: Molecule that decreases H+ concentration, often by producing OH-.

pH Equation:

Major body fluid pH: Blood pH is tightly regulated around 7.4.

Proteins: Structure and Function

Proteins as Cellular Workhorses

Proteins perform a wide range of functions in cells, including catalysis, transport, signaling, and structural support.

• Seven major functions: Enzymatic, structural, transport, signaling, regulatory, defensive, and storage.

Protein Interactions: Activation and Inhibition

Proteins interact with other molecules, which can activate or inhibit their function.

• Activation: Binding of a molecule increases protein activity.

• Inhibition: Binding of a molecule decreases protein activity.

Ligand and Binding Site

A ligand is a molecule that binds specifically to a protein's binding site. This interaction is fundamental to protein function.

• Specificity: Proteins bind only certain ligands.

• Affinity: Strength of ligand binding.

• Competition: Multiple ligands may compete for the same binding site.

• Saturation: All binding sites are occupied at high ligand concentrations.

Protein Interaction Equilibrium and Dissociation Equations

Protein-ligand binding is described by equilibrium constants.

Where is the dissociation constant, [P] is protein concentration, [L] is ligand concentration, and [PL] is the protein-ligand complex concentration.

Law of Mass Action

The law of mass action describes how the rate of a chemical reaction is proportional to the concentrations of the reactants.

Additional info: This law is crucial for understanding enzyme kinetics and protein-ligand interactions.

Factors Affecting Protein Binding

Summary and Exam Preparation

• Review key elements and atomic structure.

• Understand the roles of ions, isotopes, cations, and anions.

• Know the biological roles of electrons and types of chemical bonds.

• Distinguish between acids, bases, and pH.

• Master protein structure, function, and binding concepts.

• Practice concept check questions for exam readiness.