The Importance of Chemistry in Anatomy and Physiology

Why Study Chemistry in Anatomy & Physiology?

Chemistry is fundamental to understanding the structure and function of the human body. All anatomical structures are composed of chemicals, and all physiological processes are based on chemical reactions.

• Chemistry is concerned with the composition of substances and how they change in chemical reactions.

• The human body, food, and medications are all composed of chemicals.

• Water and electrolytes make up all body fluids, playing essential roles in physiological processes.

Fundamentals of Chemistry

Basic Definitions

• Matter: Anything that takes up space and has mass. Matter exists as solids, liquids, or gases.

• Mass: The amount of matter present in a substance.

• Weight: The heaviness of an object due to gravitational pull on its mass.

• Chemistry: The study of the composition, properties, and interactions of matter.

• Biochemistry: The branch of chemistry that studies the chemical processes within and related to living organisms.

Elements and Atoms

Elements, Compounds, and Atoms

• Elements: The simplest types of matter with specific chemical properties. There are 92 naturally occurring elements.

• Compounds: Chemical combinations of different elements.

• Atoms: The smallest particles of an element that retain the properties of that element.

Different elements are required by the body in varying amounts:

• Bulk elements: Needed in large amounts (e.g., O, H, N, S, P).

• Trace elements: Needed in small amounts (e.g., Fe, I).

• Ultratrace elements: Needed in very minute amounts (e.g., As).

Some Particles of Matter

Atoms are composed of subatomic particles, each with distinct properties:

Elements in the Human Body (By Weight)

The human body is composed of both major and trace elements, each with specific roles.

Atomic Structure

Subatomic Particles

• Protons: Large particles with a single positive charge, found in the nucleus.

• Neutrons: Large, uncharged particles, also in the nucleus.

• Electrons: Small, negatively charged particles in constant motion around the nucleus.

Atoms are electrically neutral because the number of protons equals the number of electrons.

Atomic Number and Mass Number

• Atomic Number: The number of protons in the nucleus of an atom; unique for each element.

• Mass Number: The sum of protons and neutrons in the nucleus.

• Electrons do not significantly contribute to atomic mass due to their small size.

Isotopes

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

• Some isotopes are radioactive (unstable), releasing energy or particles until they become stable. These are used in medical diagnostics and treatment.

• The atomic weight of an element is the average of the mass numbers of all its isotopes.

Molecules and Compounds

Definitions and Formulas

• Molecule: A particle formed when two or more atoms chemically combine.

• Compound: A particle formed when atoms of different elements chemically combine.

• Molecular Formula: Shows the types and numbers of atoms in a molecule (e.g., for water, for glucose).

Chemical Bonds

• Ionic Bonds: Formed when atoms transfer electrons, resulting in oppositely charged ions that attract each other.

• Covalent Bonds: Formed when atoms share electrons. Can be single, double, or triple bonds depending on the number of shared electron pairs.

• Polar Covalent Bonds: Electrons are shared unequally, resulting in molecules with partial charges (e.g., water).

• Hydrogen Bonds: Weak attractions between the slightly positive hydrogen atom of one polar molecule and the slightly negative atom (often oxygen or nitrogen) of another.

Structural Formulas

• Show how atoms are bonded and arranged in a molecule.

• Single lines represent single bonds; double lines represent double bonds.

Chemical Reactions

Types of Chemical Reactions

• Synthesis Reaction: Two or more reactants combine to form a more complex product.

• Decomposition Reaction: A complex molecule breaks down into simpler substances.

• Exchange Reaction: Parts of two molecules trade places.

• Reversible Reaction: Products can revert to original reactants.

Electrolytes, Acids, Bases, and Salts

Definitions

• Electrolytes: Substances that release ions in water, allowing the solution to conduct electricity.

• Acids: Electrolytes that release hydrogen ions () in water. Example:

• Bases: Electrolytes that release ions that can combine with hydrogen ions (often release hydroxide ions, ). Example:

• Salts: Electrolytes formed by the reaction between an acid and a base. Example:

pH Scale and Acid-Base Balance

• The pH scale measures hydrogen ion concentration in a solution, ranging from 0 (most acidic) to 14 (most basic).

• Each pH unit represents a tenfold difference in concentration.

• pH 7 is neutral (pure water), pH < 7 is acidic, pH > 7 is basic (alkaline).

• Normal blood pH is tightly regulated between 7.35 and 7.45.

• Acidosis: Blood pH drops below 7.35, causing disorientation and fatigue.

• Alkalosis: Blood pH rises above 7.45, causing dizziness and agitation.

• Buffers: Chemicals that resist pH changes by binding or releasing ions.

Chemical Constituents of Cells

Organic vs. Inorganic Molecules

• Organic molecules: Contain carbon and hydrogen; include carbohydrates, proteins, lipids, and nucleic acids.

• Inorganic molecules: Generally do not contain both carbon and hydrogen; include water, oxygen, carbon dioxide, and inorganic salts.

Inorganic Substances

• Water: Most abundant compound in living material; solvent for metabolic reactions, helps transport chemicals, and regulates temperature.

• Oxygen (): Used by cells to release energy from nutrients.

• Carbon Dioxide (): Waste product of metabolism, exhaled from the body.

• Inorganic Salts: Sources of important ions (e.g., , , , ); help regulate water balance, pH, blood clotting, nerve, and muscle function.

Organic Substances: Carbohydrates

• Main source of cellular energy.

• Contain C, H, and O, usually in a 2:1 ratio of H:O (e.g., for glucose).

• Types:

  • Monosaccharides: Single sugars (e.g., glucose, fructose).

  • Disaccharides: Double sugars (e.g., sucrose, lactose).

  • Polysaccharides: Complex carbohydrates (e.g., starch, glycogen, cellulose).

Organic Substances: Lipids

• Insoluble in water, soluble in organic solvents.

• Include triglycerides (fats), phospholipids, and steroids.

• Triglycerides: Main energy storage; composed of glycerol and three fatty acids.

• Phospholipids: Glycerol, two fatty acids, and a phosphate group; major component of cell membranes.

• Steroids: Four connected rings of carbon; include cholesterol, which is used to synthesize hormones.

• Saturated fatty acids: Only single carbon-carbon bonds; solid at room temperature; mostly animal origin.

• Unsaturated fatty acids: One or more double bonds; liquid at room temperature; mostly plant origin.

Organic Substances: Proteins

• Serve as structural materials, energy sources, hormones, receptors, enzymes, and antibodies.

• Composed of amino acids, each with an amino group (), a carboxyl group (), and a unique R group.

• Amino acids are linked by peptide bonds (between the amino group of one and the carboxyl group of another).

• Levels of protein structure:

  • Primary: Amino acid sequence.

  • Secondary: Pleated or twisted structure due to hydrogen bonding.

  • Tertiary: Unique 3D folded shape (conformation) that determines function.

  • Quaternary: Structure formed by multiple polypeptide chains.

• Denaturation: Loss of protein structure (and function) due to heat, pH, or chemicals; may be reversible or irreversible.

Organic Substances: Nucleic Acids

• Carry genetic code (DNA) or aid in protein synthesis (RNA).

• Composed of nucleotides (each with a sugar, phosphate group, and nitrogenous base).

• DNA (Deoxyribonucleic acid): Double helix; stores genetic information; contains deoxyribose sugar.

• RNA (Ribonucleic acid): Single strand; involved in protein synthesis; contains ribose sugar.

Science and Technology: Imaging Techniques

CT Scanning and PET Imaging

• Computerized Tomography (CT): Uses X-rays to create 3D images of internal anatomy; differentiates tissues with slight density differences.

• Positron Emission Tomography (PET): Uses radioactive isotopes that emit positrons to detect biochemical activity; useful for detecting brain disorders, blood flow, and physiological function.