Chemistry in Anatomy & Physiology

Basic Chemistry Concepts

Chemistry is fundamental to understanding the structure and function of the human body. Matter and energy are the building blocks of all biological processes.

• Matter: Anything that has mass or occupies space. Exists as solids, liquids, or gases.

• Energy: The capacity to do work or put matter into motion.

  • Kinetic energy: Energy in action (e.g., walking, moving ball).

  • Potential energy: Stored energy (e.g., batteries, water behind a dam).

• Forms of Energy:

  1. Chemical energy: Stored in chemical bonds (ATP is the most useful form).

  2. Electrical energy: Movement of charged particles.

  3. Mechanical energy: Directly involved in moving matter.

  4. Radiant energy: Energy that travels in waves.

Elements and Atoms

Elements are pure substances that cannot be broken down by ordinary means. Atoms are the smallest units of elements.

• Major elements in the human body: Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N) (make up 96% of body mass).

• Trace elements: Present in small amounts (e.g., calcium, sodium).

• Atoms: Composed of subatomic particles:

  • Protons: Positively charged, reside in nucleus, mass = 1 amu.

  • Neutrons: No charge, reside in nucleus, mass = 1 amu.

  • Electrons: Negatively charged, orbit nucleus, mass ≈ 0 amu.

• Atomic number: Number of protons in nucleus.

• Isotopes: Atoms with differing numbers of neutrons (e.g., radioisotopes).

Chemical Bonding

Molecules and Compounds

Molecules are formed when two or more atoms are held together by chemical bonds. Compounds consist of atoms of different elements.

• Molecule: Two or more atoms of the same element (e.g., H2).

• Compound: Two or more atoms of different elements (e.g., H2O).

• Mixtures: Two or more substances physically intermixed (solutions, colloids, suspensions).

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms, resulting in charged ions (cations and anions). Example: NaCl (sodium chloride).

• Covalent Bonds: Formed by sharing electrons between atoms. Can be single, double, or triple bonds.

  • Polar covalent: Unequal sharing, creates partial charges (e.g., H2O).

  • Nonpolar covalent: Equal sharing, no charge separation (e.g., O2).

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (common in water and DNA).

Chemical Reactions

Types of Chemical Reactions

Chemical reactions involve the making or breaking of chemical bonds, resulting in new substances.

• Synthesis Reactions: Atoms or molecules combine to form a larger, more complex molecule.

  • Example:

  • Always require energy input.

• Decomposition Reactions: Molecule is broken down into smaller molecules or atoms.

  • Example:

  • Release energy (catabolic reactions).

• Exchange Reactions: Involve both synthesis and decomposition.

  • Example:

  • Energy is created and spent (e.g., ATP cycle).

All chemical reactions are theoretically reversible.

Factors Influencing Reaction Rates

• Temperature: Higher temperature increases kinetic energy and reaction rate.

• Concentration: Higher concentration increases collision frequency.

• Particle Size: Smaller particles move faster and react more quickly.

• Catalysts: Enzymes that increase reaction rates without being consumed.

Biochemistry: Inorganic and Organic Compounds

Inorganic Chemistry

• Water: Most abundant inorganic compound in living material (60–80% of cell mass).

  • High heat capacity and vaporization.

  • Polar solvent properties (universal solvent).

  • Reactivity (hydrolysis reactions).

  • Cushioning (protects organs).

• Salts: Ionic compounds that dissociate in water, forming electrolytes (e.g., NaCl, KCl).

• Acids and Bases: Substances that release H+ (acids) or OH- (bases) in solution.

  • pH scale: Measures H+ concentration, ranges from 0–14.

    • pH < 7: Acidic

    • pH = 7: Neutral

    • pH > 7: Alkaline

  • Body buffers pH changes to maintain homeostasis.

Organic Chemistry

Organic molecules are unique to living systems and include carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.

• Primary function: Provide cellular fuel.

• Classified by size and solubility:

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

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

  • Polysaccharides: Many sugars linked together (e.g., starch, cellulose).

Lipids

• Large, water-insoluble molecules; dissolve in organic solvents.

• Contain carbon, hydrogen, oxygen, and sometimes phosphorus.

• Major types:

  • Triglycerides: Neutral fats, energy storage.

  • Phospholipids: Modified triglycerides, major component of cell membranes.

  • Steroids: Four interlocking hydrocarbon rings (e.g., cholesterol).

  • Prostaglandins: Key to various body processes.

Proteins

• Make up 10–30% of cell mass; most varied function in the body.

• Composed of amino acids (20 types), each with an amino group and acid group.

• Amino acids join via dehydration synthesis to form peptide bonds.

• Levels of protein structure:

  1. Primary: Sequence of amino acids.

  2. Secondary: Alpha helix or beta sheet formation.

  3. Tertiary: 3D folding of polypeptide.

  4. Quaternary: Multiple polypeptides joined.

• Functions: Enzymes, hemoglobin, contractile proteins.

Nucleic Acids

• DNA: Stores genetic information; double helix structure.

• RNA: Involved in protein synthesis; single-stranded.

• Difference: DNA contains deoxyribose, RNA contains ribose.

ATP (Adenosine Triphosphate)

• Main energy currency of the cell.

• Provides energy for cellular processes.

HTML Table: Comparison of Chemical Bonds

HTML Table: Levels of Protein Structure

Key Equations

• General Synthesis Reaction:

• General Decomposition Reaction:

• General Exchange Reaction:

• pH Calculation:

Summary

• Chemistry underpins all biological processes in Anatomy & Physiology.

• Understanding matter, energy, elements, atoms, and chemical bonds is essential for grasping cellular and molecular functions.

• Biochemistry covers the structure and function of water, salts, acids, bases, carbohydrates, lipids, proteins, and nucleic acids.

• ATP is the primary energy molecule in cells.