Basic Chemistry

Matter and Energy

Understanding the chemical basis of life is essential for studying anatomy and physiology. Matter and energy are foundational concepts in chemistry and biology.

• Matter: Anything that occupies space and has mass.

• Energy: The capacity to do work or cause change (not detailed in the provided notes, but essential context).

Composition of Matter

• Elements: Fundamental units of matter; cannot be broken down by ordinary chemical means.

• 96% of the human body is composed of four elements:

  • Oxygen (O): 65% of body mass; most abundant element in the body.

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

• The periodic table lists all known elements.

Atoms and Atomic Structure

Atoms are the smallest units of elements that retain their properties.

• Atomic symbol: Chemical shorthand for each element (e.g., H for hydrogen).

• Subatomic particles:

  • Protons (p+): Positively charged; found in the nucleus.

  • Neutrons (n0): Neutral (no charge); found in the nucleus.

  • Electrons (e-): Negatively charged; orbit the nucleus in electron shells.

• Atoms are electrically neutral: number of protons equals number of electrons.

• Ions: Atoms that have gained or lost electrons, resulting in a net charge.

• Electrons determine chemical behavior and bonding properties.

Molecules and Compounds

• Molecule: Two or more atoms of the same element chemically combined.

  • Example:

• Compound: Two or more atoms of different elements chemically combined.

  • Example: (methane)

Chemical Bonds and Chemical Reactions

Chemical bonds form when atoms interact to achieve stable electron configurations, especially in their outermost (valence) shells.

• Electron shells:

  • Shell 1: max 2 electrons

  • Shell 2: max 8 electrons

  • Shell 3: max 18 electrons

  • Subsequent shells can hold more electrons

• Valence shell: Outermost electron shell; determines bonding behavior.

• Rule of eights (Octet rule): Atoms are stable when their valence shell has 8 electrons (except for the first shell, which is stable with 2).

• Atoms with incomplete valence shells are reactive and will gain, lose, or share electrons to achieve stability.

Types of Chemical Bonds

• Ionic bonds: Formed when electrons are completely transferred from one atom to another.

  • Creates ions:

    • Anion: Negatively charged (gains electrons)

    • Cation: Positively charged (loses electrons)

  • Opposite charges attract, holding ions together.

• Covalent bonds: Formed when atoms share electrons.

  • Electrons are shared in pairs.

  • Nonpolar covalent bonds: Electrons shared equally; molecule is electrically neutral (e.g., carbon dioxide).

  • Polar covalent bonds: Electrons shared unequally; molecule has positive and negative poles (e.g., water).

Patterns of Chemical Reactions

• Synthesis reaction: Atoms/molecules combine to form a larger molecule; energy is absorbed.

  • General form:

• Decomposition reaction: Molecule is broken down into smaller molecules; energy is released.

  • General form:

Biochemistry: The Chemical Composition of Living Matter

Inorganic Compounds

• Inorganic compounds: Do not contain carbon (with some exceptions); usually small and simple.

  • Examples: water, salts, many acids and bases

• Water: Most abundant inorganic compound; about two-thirds of body weight.

• Salts: Ionic compounds (cations other than H+, anions other than OH-); dissociate in water to form electrolytes.

  • Vital for nerve impulses (e.g., sodium and potassium ions).

• Acids: Electrolytes that release hydrogen ions (H+); proton donors.

  • Example:

• Bases: Electrolytes that release hydroxyl ions (OH-); proton acceptors.

  • Example:

• pH: Measures the concentration of hydrogen ions in solution.

  • Scale: 0 (most acidic) to 14 (most basic); 7 is neutral.

  • Each pH unit represents a tenfold change in H+ concentration.

  • Acidic: pH < 7 (more H+ than OH-)

  • Basic: pH > 7 (fewer H+ than OH-)

  • Buffers: Chemicals that help regulate pH changes.

Organic Compounds

• Organic compounds: Contain carbon; large, covalently bonded molecules.

  • Include carbohydrates, lipids, proteins, and nucleic acids.

• Polymers: Chainlike molecules made of repeating units (monomers).

• Dehydration synthesis: Joins monomers to form polymers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

• Contain carbon, hydrogen, and oxygen.

• Include sugars and starches.

• Classified by size:

  • Monosaccharides: Simple sugars; single-chain or ring structures (3–7 carbons).

    • Examples: glucose, fructose, galactose, ribose, deoxyribose

  • Disaccharides: Two monosaccharides joined by dehydration synthesis.

    • Examples: sucrose, lactose, maltose

  • Polysaccharides: Long, branching chains of monosaccharides; storage molecules.

    • Examples: starch (plants), glycogen (animals)

Lipids

• Contain carbon, hydrogen, and oxygen (less oxygen than carbohydrates).

• Insoluble in water; soluble in other lipids.

• Main types:

  • Triglycerides (neutral fats): Composed of glycerol and three fatty acids; energy storage.

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

    • Hydrophilic ("water-loving") head; hydrophobic ("water-fearing") tails.

  • Steroids: Four fused carbon rings (e.g., cholesterol, hormones; not detailed in the notes).

Proteins

• Contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Built from amino acids (monomers).

• Functions:

  • Structural (e.g., collagen, keratin)

  • Functional (e.g., enzymes, hormones, antibodies)

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

• Globular proteins: Functional roles (e.g., enzymes, antibodies); have complex tertiary structure.

Nucleic Acids

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

• Largest biological molecules; form genes.

• Monomer: Nucleotide, composed of:

  1. Nitrogenous base

  2. Pentose (five-carbon) sugar

  3. Phosphate group

• Two major types:

  • DNA (Deoxyribonucleic acid): Genetic material in the nucleus; instructions for protein synthesis.

  • RNA (Ribonucleic acid): Carries out DNA's instructions for protein synthesis.

Adenosine Triphosphate (ATP)

• Composed of ribose sugar, adenine base, and three phosphate groups.

• Primary energy carrier in cells.

• Energy is released by breaking high-energy phosphate bonds.

Summary Table: Major Classes of Organic Compounds

Additional info: Some explanations (e.g., energy, steroids, and the role of ATP) were expanded for clarity and completeness.