Basic Principles of Chemistry in Anatomy & Physiology

Objective 2: Basic Principles of Chemistry

2.0 Basic Principles of Chemistry as They Apply to Body Processes

Chemistry is fundamental to understanding physiological processes in the human body. All body functions, from movement to digestion and nervous system activity, are governed by chemical reactions and interactions.

• Chemistry underlies all physiological reactions:

  • Movement

  • Digestion

  • Pumping of the heart

  • Nervous system function

• Branches of chemistry relevant to the body:

  • Basic chemistry

  • Biochemistry

2.1 Key Terms Related to Basic Chemistry

Elements and Atoms

All matter is composed of elements, which are substances that cannot be broken down into simpler substances by ordinary chemical methods.

• Major elements in the body:

  • Carbon, oxygen, hydrogen, nitrogen (make up 96% of body mass)

  • 11 elements make up <0.01% of body mass

• Atoms:

  • Smallest particles of an element with properties of that element

  • Atoms give each element its particular physical and chemical properties

Molecules and Compounds

• Molecule: General term for two or more atoms bonded together

• Compound: Specific molecule that has two or more different kinds of atoms bonded together (e.g., CaCl2)

• Molecules with only one type of atom (O2, H2) are just called molecules

Mixtures

Most matter exists as mixtures: two or more components physically intermixed.

• Three basic types of mixtures:

  1. Solutions

  2. Colloids

  3. Suspensions

Type	Description	Example
Solution	Homogeneous mixture; solute particles are evenly distributed	Salt water
Colloid	Heterogeneous mixture; solute particles are not evenly distributed, but do not settle out	Gelatin, cytosol
Suspension	Heterogeneous mixture; large, visible solute particles settle out	Blood (if left to sit)

Differences Between Mixtures and Compounds

• Mixtures do not involve chemical bonding between components

• Mixtures can be separated by physical means; compounds by breaking chemical bonds

• Mixtures can be homogeneous or heterogeneous; compounds are only homogeneous

Chemical Reactions

Chemical reactions occur when chemical bonds are formed, rearranged, or broken.

• Reactants: Substances entering into reaction together

• Products: Resulting chemicals at end of reaction

Types of Chemical Reactions

• Synthesis: Combination of atoms or molecules to form larger molecules

• Decomposition: Breakdown of a molecule into smaller molecules or atoms

• Exchange: Involves both synthesis and decomposition; atoms are exchanged between molecules

Energy in Chemical Reactions

• Exergonic reactions: Release energy

• Endergonic reactions: Absorb energy

Factors Affecting Reaction Rate

• Temperature: Higher temperature increases rate

• Concentration of reactants: Higher concentration increases rate

• Particle size: Smaller particles increase rate

• Catalysts: Increase rate without being chemically changed; enzymes are biological catalysts

2.2 Organic and Inorganic Chemistry

Biochemistry

Biochemistry is the study of the chemical composition and reactions of living matter. Chemicals in the body are classified as organic or inorganic compounds.

• Organic compounds: Contain carbon and are covalently bonded; include carbohydrates, lipids, proteins, and nucleic acids

• Inorganic compounds: Include water, salts, acids, and bases; generally lack carbon

Water

• Most abundant inorganic compound in the body (60-80% of cell volume)

• High heat capacity and heat of vaporization

• Polar solvent properties

• Reactivity (hydrolysis and dehydration synthesis)

• Cushioning (protects organs)

Salts

• Salts: Ionic compounds that dissociate in water to form ions

• Common body salts: NaCl, CaCO3, KCl

• Important for nerve impulse transmission and muscle contraction

Example dissociation equation:

$\mathrm{HCl} \rightarrow \mathrm{H}^+ + \mathrm{Cl}^-$

Acids and Bases

• Acids: Release hydrogen ions ($\mathrm{H}^+$) in solution

• Bases: Take up hydrogen ions or release hydroxide ions ($\mathrm{OH}^-$)

• Measured in pH units:

  • pH 7 = neutral

  • pH < 7 = acidic

  • pH > 7 = alkaline (basic)

Buffer Systems

• Buffers resist abrupt and large swings in pH

• Release or bind hydrogen ions to maintain pH stability

Organic Compounds

• Carbohydrates: Sugars and starches; provide energy and structural support

  • Monosaccharides: Simple sugars (glucose, fructose)

  • Disaccharides: Two monosaccharides joined (sucrose, lactose)

  • Polysaccharides: Long chains of monosaccharides (starch, glycogen)

• Lipids: Insoluble in water; include triglycerides, phospholipids, steroids

  • Triglycerides: Energy storage, insulation, protection

  • Phospholipids: Major component of cell membranes

  • Steroids: Cholesterol, hormones

• Proteins: Structural material, enzymes, transport, movement

  • Composed of amino acids

  • Fibrous proteins (collagen) and globular proteins (enzymes, antibodies)

• Nucleic Acids: DNA and RNA; store and transmit genetic information

Examples and Applications

• Glycogen: Storage carbohydrate in animals

• Starch: Storage carbohydrate in plants

• Enzymes: Biological catalysts for metabolic reactions

• Cholesterol: Precursor for steroid hormones and vitamin D synthesis

Summary Table: Major Classes of Biomolecules

Class	Main Elements	Function	Example
Carbohydrates	C, H, O	Energy, structure	Glucose, glycogen
Lipids	C, H, O	Energy storage, membranes, hormones	Triglycerides, phospholipids, cholesterol
Proteins	C, H, O, N, S	Structure, enzymes, transport	Collagen, hemoglobin, enzymes
Nucleic Acids	C, H, O, N, P	Genetic information	DNA, RNA

Additional info: The notes expand on the definitions and functions of key chemical concepts as they relate to human physiology, including the importance of water, salts, acids, bases, and biomolecules in maintaining homeostasis and supporting life processes.