Basic Chemistry for Anatomy & Physiology

Basic Chemistry

Introduction to Matter and Energy

Chemistry is foundational to understanding anatomy and physiology, as all body processes depend on chemical interactions. Matter is anything that occupies space and has mass, and it exists in three states: solid, liquid, and gas. Energy is the ability to do work and exists in various forms within the body.

• States of Matter:

  • Solid: Definite shape and volume.

  • Liquid: Definite volume, shape of container.

  • Gas: Neither definite shape nor volume.

• Physical vs. Chemical Changes:

  • Physical changes do not alter the basic nature of a substance (e.g., melting ice).

  • Chemical changes alter the chemical composition (e.g., burning wood).

• Forms of Energy:

  • Chemical energy: Stored in bonds of substances (e.g., ATP).

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

  • Mechanical energy: Directly moves matter (e.g., muscle contraction).

  • Radiant energy: Travels in waves (e.g., light, X-rays).

• Energy Conversion: ATP (adenosine triphosphate) stores and releases energy for cellular work.

Composition of Matter

All matter is composed of elements, which are substances that cannot be broken down into simpler substances by ordinary chemical means. The human body is primarily made of four elements: oxygen, carbon, hydrogen, and nitrogen.

• Elements: Fundamental units of matter; listed in the periodic table.

• Major Elements in the Body: Oxygen (65%), Carbon, Hydrogen, Nitrogen (total 96%).

• Lesser and Trace Elements: Include calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iron, and trace elements like zinc and copper, which are essential in small amounts for enzyme function.

Element Type	Examples	Body Function
Major	O, C, H, N	Structure, metabolism
Lesser	Ca, P, K, S, Na, Cl, Mg, Fe	Bone, nerve, muscle, blood
Trace	Zn, Cu, Se, etc.	Enzyme activation

Atomic Structure

Atoms are the smallest units of elements, consisting of protons, neutrons, and electrons. The arrangement of these subatomic particles determines the chemical properties of an element.

• Protons: Positively charged, in the nucleus.

• Neutrons: Neutral, in the nucleus.

• Electrons: Negatively charged, orbit the nucleus.

• Atomic Number: Number of protons; unique to each element.

• Atomic Mass Number: Protons + neutrons.

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

• Radioisotopes: Unstable isotopes that decay, emitting radiation; used in medical imaging and tracing biological processes.

Molecules and Compounds

Molecules are formed when two or more atoms bond together. Compounds are molecules composed of different elements. Chemical bonds hold atoms together and determine the properties of substances.

• Molecule: Two or more atoms of the same element (e.g., O2).

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

• Chemical Bonds: Energy relationships between electrons of reacting atoms.

Types of Chemical Bonds

• Ionic Bonds: Formed by transfer of electrons; create ions (cations and anions) that attract each other.

• Covalent Bonds: Formed by sharing electrons; can be nonpolar (equal sharing) or polar (unequal sharing).

• Hydrogen Bonds: Weak bonds between hydrogen and electronegative atoms (e.g., in water, proteins, DNA).

Chemical Reactions

Chemical reactions involve the making or breaking of bonds. They are essential for all physiological processes.

• Synthesis (Anabolic) Reactions: Build larger molecules from smaller ones; energy is absorbed.

• Decomposition (Catabolic) Reactions: Break down molecules; energy is released.

• Exchange Reactions: Involve both synthesis and decomposition; atoms are rearranged.

• Reversible Reactions: Can proceed in both directions; indicated by double arrows.

Inorganic Compounds

Inorganic compounds do not contain carbon (with some exceptions) and include water, salts, acids, and bases.

• Water: Most abundant inorganic compound; high heat capacity, solvent, reactive, cushioning.

• Salts: Ionic compounds that dissociate in water; vital for nerve and muscle function.

• Acids: Release hydrogen ions (H+); proton donors.

• Bases: Release hydroxyl ions (OH-); proton acceptors.

• pH Scale: Measures hydrogen ion concentration; 0-14 scale, 7 is neutral, below 7 acidic, above 7 basic.

• Buffers: Chemicals that resist changes in pH.

Organic Compounds

Organic compounds contain carbon and are typically large, covalently bonded molecules. They include carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Sugars and starches; provide energy.

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

  • Disaccharides: Two monosaccharides joined (e.g., sucrose).

  • Polysaccharides: Long chains (e.g., glycogen, starch).

• Lipids: Fats and oils; energy storage, cell membranes, hormones.

  • Triglycerides: Glycerol + 3 fatty acids; saturated (solid) or unsaturated (liquid).

  • Phospholipids: Main component of cell membranes.

  • Steroids: Cholesterol-based molecules (e.g., hormones).

• Proteins: Made of amino acids; structure, enzymes, hormones, antibodies.

  • Levels of Structure: Primary, secondary, tertiary, quaternary.

  • Fibrous proteins: Structural (e.g., collagen).

  • Globular proteins: Functional (e.g., enzymes).

• Nucleic Acids: DNA and RNA; genetic information and protein synthesis.

  • Nucleotides: Building blocks (sugar, phosphate, base).

  • DNA: Double helix, genetic code.

  • RNA: Single strand, protein synthesis.

• ATP (Adenosine Triphosphate): Main energy carrier in cells; energy released by breaking phosphate bonds. $\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$