The Chemical Level of Organization

The Chemical Level of Organization

Overview of Chemistry

  • Chemistry is defined as the science of change.

  • Topics covered in this chapter include:

    • The structure of atoms

    • The basic chemical building blocks

    • How atoms combine to form increasingly complex structures

Hierarchy of Body Structures

  • Levels of Organization:

    • Atomic Level:

    • Explanation: Atoms are the smallest unit of an element that retains the element's properties.

    • Example: Carbon, Hydrogen, Oxygen.

    • Molecular Level:

    • Explanation: Atoms combine to form molecules, which can have properties different from the atoms they contain.

    • Example: Water, DNA, Carbohydrates.

    • Cellular Level:

    • Explanation: Cells are the smallest units of life, enclosed by a membrane or cell wall and often performing specific functions in multicellular organisms.

    • Example: Muscle cells, Skin cells, Neurons.

    • Tissue Level:

    • Explanation: Tissues are groups of cells with similar functions.

    • Examples: Muscle, Epithelial, Connective tissues.

    • Organ Level:

    • Explanation: Organs consist of two or more types of tissues working together for specific tasks.

    • Examples: Heart, Liver, Stomach.

    • Organ System Level:

    • Explanation: An organ system comprises a group of organs that manage a more generalized set of functions.

    • Examples: Digestive System, Circulatory System.

    • Organismal Level:

    • Explanation: An organism comprises several organ systems functioning together.

    • Example: Humans.

Atoms and Atomic Structure

  • Matter:

    • Made up of atoms.

    • Atoms combine to form chemicals with different characteristics, influencing physiology at molecular and cellular levels.

Atomic Structure

  • Atoms: The smallest stable units of matter.

  • Composition: Made up of subatomic particles:

    • Protons (p+): Positive charge.

    • Neutrons (n or n⁰): Electrically neutral (no charge).

    • Electrons (e-): Negative charge, much smaller than protons or neutrons (approximately 1/1836 the mass).

Mass Distribution in the Universe

  • Atoms account for approximately:

    • 4.9% of matter

    • 26.8% dark matter

    • 68.3% dark energy.

Structure within the Atom

  • Nucleus:

    • Central part of the atom containing protons and possibly neutrons.

    • The mass of the atom is primarily determined by the number of protons and neutrons present.

  • Electron Cloud:

    • Formed by electrons orbiting the nucleus.

Interaction of Atoms

  • Atoms interact through their electrons to form larger structures, such as compounds or molecules.

Atomic Characteristics

  • Atomic Number: The number of protons in an atom.

  • Isotopes: Atoms with the same number of protons but different numbers of neutrons; identical chemical properties yet different mass numbers.

  • Atomic Mass: Actual mass of an atom of a specific isotope, measured in atomic mass units (amu) or daltons.

    • Example: One amu ≈ 1/12 mass of a carbon-12 atom.

  • Atomic Weight: The average mass of an element, taking into account different isotopes. Example: Hydrogen has an atomic weight of 1.0079 with some isotopes having neutrons.

Chemical Elements

  • All elements represent a chemical symbol based on their names.

    • Example: O for oxygen, C for carbon, Na for sodium (from Latin natrium).

Principal Elements of the Human Body

  • Element Composition (% of total body weight):

    • Oxygen (O): 65% - Component of water and essential for respiration.

    • Carbon (C): 18.6% - Found in all organic compounds.

    • Hydrogen (H): 9.7% - Component of water and other compounds in the body.

    • Nitrogen (N): 3.2% - Found in proteins and nucleic acids.

    • Calcium (Ca): 1.8% - Found in bones and important for various bodily functions.

    • Phosphorus (P): 1.0% - Found in nucleic acids and high-energy compounds.

    • Potassium (K): 0.4% - Important for nerve impulses.

    • Sodium (Na): 0.2% - Regulates blood volume and nerve impulses.

Electrons and Energy Levels

  • Energy Levels:

    • The outermost energy level (valence shell) represents the atom's surface.

    • Atoms with unfilled outer shells are reactive.

    • Example Atoms: Hydrogen, Lithium.

    • Atoms with full outer shells are inert (non-reactive).

    • Example Elements: Helium, Neon (noble gases).

Ion Formation

  • Atoms that lose or gain electrons form ions:

    • Cations: Positively charged ions created when an atom loses electrons (e.g., Na+).

    • Anions: Negatively charged ions created when an atom gains electrons (e.g., Cl–).

Chemical Bonds

  • The two most common types of chemical bonds are:

    • Ionic Bonds:

    • Created by electrical attraction between cations and anions.

    • Involves the transfer of electrons to achieve stability.

    • Example: Formation of sodium chloride (NaCl).

    • Covalent Bonds:

    • Involve the sharing of electrons between atoms, forming molecules.

    • Types include:

      • Single Covalent Bonds: Share one pair of electrons.

      • Double Covalent Bonds: Share two pairs of electrons.

Molecular Characteristics

  • Hydrophilic: Molecules that readily interact with water; examples include sugars.

  • Hydrophobic: Nonpolar molecules that do not readily interact with water; examples include fats and oils.

States of Matter

  • Matter exists in three states:

    1. Solid: Particles are tightly packed; maintains volume and shape.

    2. Liquid: Particles held less tightly; has a constant volume determined by the container's shape.

    3. Gas: Particles are independent; has neither a constant volume nor a fixed shape, can be compressed or expanded.

Chemical Reactions and Energy Transfer

  • Chemical reactions are critical for cellular functions, involving the formation and breaking of chemical bonds.

  • Reactants: The atoms and molecules participating in a reaction.

  • Products: The resulting substances after a reaction.

  • Metabolism: The total of all chemical reactions occurring in the body.

Energy in Chemical Reactions

  • Kinetic Energy: Energy of motion, can be transferred to perform work (e.g., muscles contracting).

  • Potential Energy: Stored energy with the potential to do work (e.g., stretched springs).

  • Energy conversion is not 100% efficient; some energy is lost as heat.

Chemical Notation

  • Molecular Representation:

    • Subscripts indicate the number of atoms in a molecule.

    • Example: H2 = hydrogen molecule (2 hydrogen atoms).

    • Chemical Equations:

    • Represent chemical reactions with reactants on the left and products on the right.

    • Example: 2 H + O → H2O.

Types of Chemical Reactions

  • Decomposition Reactions: Break molecules into smaller fragments, including hydrolysis, which involves water.

  • Synthesis Reactions: Assemble smaller molecules into larger ones, such as dehydration synthesis, where water is removed.

  • Exchange Reactions: Involve shuffling parts of reacting molecules to form new products.

Enzymes

  • Enzymes lower the activation energy necessary for reactions, promoting their occurrence under life-compatible conditions. Enzymes act as catalysts and are not permanently altered.

  • Metabolites: Substances synthesized or broken down in the body via enzymatic reactions.

Water in the Body

  • Water is the most important body component, making up about 2/3 of total body weight.

  • It acts as a chemical reactant and solvent; necessary for various physiological processes.

Properties of Water

  • Solvent: Dissolves inorganic and organic molecules (aqueous solutions).

  • Forms hydration spheres around ions, with anions surrounded by positive poles and cations surrounded by negative poles of water.

pH Regulation

  • pH: A measure of H+ concentration in solutions, influencing body fluid functions.

  • Ranges from 0 (acidic) to 14 (alkaline), with 7 being neutral.

  • Buffers: Compounds that help stabilize pH by removing or adding H+ ions.

Organic Compounds

  • Definition: Compounds containing carbon and hydrogen.

  • Includes functional groups, which determine the behavior and properties of the compounds, such as:

    • Amino Group (-NH2): Acts as a base.

    • Carboxyl Group (-COOH): Acts as an acid.

    • Hydroxyl Group (-OH): Impacts solubility and can link molecules.

    • Phosphate Group (-PO4²-): Involved in energy transfer and storage.

Carbohydrates

  • Organic molecules consisting mostly of carbon, hydrogen, and oxygen.

  • Types include:

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

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

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

Lipids

  • Composed primarily of carbon, hydrogen, and oxygen, with ratios differing from carbohydrates.

  • Include fatty acids, which can be saturated or unsaturated.

Diverse Functions of Lipids

  • Important for cell membranes, energy reserves, and additional biological functions such as steroid hormones.

Proteins

  • Composed of amino acids, the most abundant organic molecules in the body.

  • Proteins have four structural levels: primary, secondary, tertiary, and quaternary structures that determine their functions.

Nucleic Acids

  • Include DNA and RNA, vital for storing and transferring genetic information.

  • Composed of nucleotides, consisting of a phosphate group, sugar, and nitrogenous bases (A, T, C, G for DNA; A, U, C, G for RNA).