Life Chemistry: Foundations for Anatomy & Physiology

Introduction to Chemistry in Life

Chemistry is fundamental to understanding the structure and function of the human body. All physiological processes depend on chemical interactions at the molecular and atomic levels. This chapter covers the basic chemical principles essential for Anatomy & Physiology students.

Forms of Matter and Energy

Types of Matter

• Solid: Definite shape and volume (e.g., bones).

• Liquid: Definite volume, changeable shape (e.g., blood plasma).

• Gas: Changeable shape and volume (e.g., oxygen in lungs).

Forms of Energy

• Chemical Energy: Stored in chemical bonds; released during chemical reactions.

• Electrical Energy: Movement of charged particles (e.g., nerve impulses).

• Mechanical Energy: Directly involved in moving matter (e.g., muscle contraction).

• Radiant/Electromagnetic Energy: Energy traveling in waves (e.g., light, X-rays).

Kinetic vs. Potential Energy

• Kinetic Energy: Energy in action (e.g., moving ions).

• Potential Energy: Stored energy (e.g., energy stored in ATP).

Atoms and Elements

Structure of Atoms

• Protons: Positively charged particles in the nucleus.

• Neutrons: Uncharged particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Key Atomic Terms

• Atomic Number: Number of protons in an atom.

• Mass Number: Total number of protons and neutrons.

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

• Atomic Weight: Average mass of all isotopes of an element.

Major Elements in the Human Body

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

Chemical Bonds

Types of Chemical Bonds

• Ionic Bonds: Transfer of electrons from one atom to another, forming cations (+) and anions (−). Example: NaCl.

• Covalent Bonds: Sharing of electron pairs between atoms. Can be single, double, or triple bonds.

• Polar Covalent Bonds: Unequal sharing of electrons (e.g., water molecules).

• Non-Polar Covalent Bonds: Equal sharing of electrons (e.g., O2).

• Hydrogen Bonds: Weak bonds between hydrogen and electronegative atoms (important in water and DNA structure).

Water and Its Properties

Importance of Water

• High Heat Capacity: Absorbs and releases heat slowly, stabilizing body temperature.

• High Heat of Vaporization: Requires significant energy to evaporate, aiding cooling (sweating).

• Universal Solvent: Dissolves many substances, facilitating chemical reactions.

• Reactivity: Involved in hydrolysis and dehydration synthesis reactions.

• Cushioning: Protects organs (e.g., cerebrospinal fluid).

Acids, Bases, and pH

pH Scale

• Measures concentration of hydrogen ions (H+) in solution.

• Scale ranges from 0 (strong acid) to 14 (strong base); 7 is neutral.

• Blood pH: 7.35–7.45 (slightly basic).

Buffers

• Resist abrupt changes in pH.

• Carbonic Acid-Bicarbonate System: Main buffer in blood.

• Regulated by kidneys, lungs, and chemical buffers.

Neutralization Reaction

• Mixing acids (H+) and bases (OH−) forms water and neutralizes pH.

Chemical Reactions and Enzymes

Factors Affecting Reaction Rates

• Temperature: Higher temperature increases reaction speed.

• Particle Size: Smaller particles react faster.

• Concentration: Higher concentration increases reaction rate.

• Catalysts/Enzymes: Speed up reactions by lowering activation energy.

Enzymes

• Globular proteins acting as biological catalysts.

• Provide active sites for substrates, increasing reaction speed.

• Lower activation energy required for reactions.

Inorganic Compounds

Salts

• Contain cations and anions (other than H+ and OH−).

• Act as electrolytes, conducting electrical currents in the body.

Oxygen and Carbon Dioxide

• Oxygen (O2): Required for aerobic respiration; 21% of atmosphere.

• Carbon Dioxide (CO2): Waste product of metabolism; must be removed from the body.

Organic Compounds

Carbohydrates

• Composed of C, H, O.

• Monosaccharides: Simple sugars (e.g., glucose).

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

• Polysaccharides: Polymers of monosaccharides (e.g., starch, glycogen, cellulose).

• Functions: Main energy source, structural roles (e.g., ribose in RNA).

Lipids

• Composed of C, H, O (sometimes P).

• Insoluble in water.

• Neutral Fats/Triglycerides: Glycerol + 3 fatty acids; energy storage, insulation, protection.

• Phospholipids: Glycerol + 2 fatty acids + phosphate group; main component of cell membranes.

• Steroids: Four interlocking rings; cholesterol is most important, precursor for vitamin D, bile salts, hormones.

• Eicosanoids: Derived from fatty acids; roles in inflammation, blood clotting, labor contractions.

Saturation of Fatty Acids

• Saturated: Single bonds, solid at room temperature.

• Unsaturated: One or more double bonds, liquid at room temperature.

Proteins

• Composed of C, H, O, N (sometimes S, P).

• Monomers: Amino acids (20 types), linked by peptide bonds.

• Fibrous Proteins: Structural, water-insoluble (e.g., collagen, keratin).

• Globular Proteins: Functional, water-soluble (e.g., enzymes, antibodies, hormones).

• Denaturation: Loss of structure and function due to pH or temperature changes.

• Essential Amino Acids: Must be obtained from diet.

Nucleic Acids

• Composed of nucleotides (Adenine, Guanine, Cytosine, Thymine, Uracil).

• DNA (Deoxyribonucleic Acid): Double-stranded, found in nucleus, stores genetic information, replicates before cell division.

• RNA (Ribonucleic Acid): Single-stranded, involved in protein synthesis (mRNA, tRNA, rRNA).

Adenosine Triphosphate (ATP)

• Main energy currency of the cell.

• Energy released by breaking phosphate bonds (phosphorylation).

• Used for cellular work (muscle contraction, active transport, synthesis reactions).

Key Chemical Reactions in Physiology

Dehydration Synthesis

• Removes water to bond molecules together (e.g., forming proteins, polysaccharides).

Hydrolysis

• Adds water to split molecules (e.g., digestion of macromolecules).

Summary Table: Major Organic Molecules

Practice Questions

• What makes up an atom? Protons, neutrons, electrons

• What type of bonds link amino acids? Peptide bonds

• What is an isotope? Same number of protons, different number of neutrons

• What bonds exist between water molecules? Hydrogen bonds

• What is a covalent bond? Atoms share one or more electron pairs

• What is an enzyme? Protein that speeds up chemical reactions

• What are the four most abundant atoms in the human body? C, H, O, N

• How does an enzyme speed up a reaction? Lowers activation energy

• What does pH measure? Concentration of H+ ions

• What causes protein denaturation? pH or temperature changes

• What is the pH of blood? 7.35–7.45 (slightly basic)

• What is dehydration synthesis? Removes water to bond molecules together

• What is hydrolysis? Splits molecules by adding water

• What buffers blood? Carbonic acid-bicarbonate system

• What is a triglyceride? Glycerol + 3 fatty acids

• What are proteins made of? Amino acids

Additional info: Some explanations and examples have been expanded for clarity and completeness, following standard Anatomy & Physiology textbooks.