Chapter 1 – The Human Body: An Orientation

Levels of Structural Organization

The human body is organized into hierarchical levels, each building upon the previous to form the complete organism.

• Chemical Level: Atoms combine to form molecules.

• Cellular Level: Cells are made up of molecules.

• Tissue Level: Tissues consist of similar types of cells.

• Organ Level: Organs are made up of different types of tissues.

• Organ System Level: Organ systems consist of different organs that work together closely.

• Organismal Level: The human organism is made up of many organ systems.

Example: Muscle cells (cellular level) form muscle tissue, which is part of the heart (organ level), contributing to the cardiovascular system (organ system level).

Necessary Functions of Life

• Maintaining boundaries (e.g., cell membranes, skin)

• Movement (muscular system, movement of substances)

• Responsiveness (ability to sense and respond to stimuli)

• Digestion (breakdown of ingested food)

• Metabolism (all chemical reactions in the body)

• Excretion (removal of wastes)

• Reproduction (cellular and organismal levels)

• Growth (increase in size and number of cells)

Survival Needs

• Nutrients (chemicals for energy and cell building)

• Oxygen (required for metabolic reactions)

• Water (most abundant chemical in the body)

• Normal body temperature (necessary for chemical reactions)

• Appropriate atmospheric pressure (for proper breathing and gas exchange)

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite changes in the external environment.

• Homeostatic Control Mechanisms: Involve a receptor (detects change), control center (processes information), and effector (responds to change).

• Feedback Mechanisms:

  • Negative Feedback: Reduces or shuts off the original stimulus (e.g., regulation of body temperature, blood glucose levels).

  • Positive Feedback: Enhances the original stimulus (e.g., blood clotting, labor contractions).

• Homeostatic Imbalance: Disturbance of homeostasis, often resulting in disease.

Chapter 2 – Chemistry Comes Alive

Common Elements in the Human Body

• The Big 4: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N)

• Other Important Elements: Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg), Iron (Fe)

Atomic Structure

• Subatomic Particles: Protons (+), Neutrons (0), Electrons (–)

• Nucleus: Contains protons and neutrons; electrons orbit the nucleus in shells (orbitals).

• Atomic Number: Number of protons in the nucleus (determines element identity).

• Atomic Mass: Number of protons + neutrons.

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

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Ions: Atoms that have gained or lost electrons.

  • Cation: Positively charged (lost electrons)

  • Anion: Negatively charged (gained electrons)

Example: Sodium (Na) loses one electron to become Na+ (cation); Chlorine (Cl) gains one electron to become Cl– (anion).

Reading the Periodic Table

• Each element is identified by its atomic number, symbol, and atomic mass.

• Groups and periods indicate similar chemical properties and electron configurations.

Molecules, Compounds, and Mixtures

• Molecule: Two or more atoms bonded together (e.g., O2).

• Compound: Two or more different elements bonded together (e.g., H2O).

• Mixtures: Physical combinations of substances.

  • Solutions: Homogeneous mixtures; solute dissolved in solvent.

    • Solute: Substance dissolved (e.g., salt).

    • Solvent: Substance doing the dissolving (e.g., water).

    • Concentration: Expressed as percent, molarity (M), or molality.

  • Colloid: Heterogeneous mixture with larger particles that do not settle (e.g., cytosol).

  • Suspension: Heterogeneous mixture with large particles that settle out (e.g., blood cells in plasma).

Chemical Bonds

• Role of Electrons: Electrons in the outer shell (valence electrons) determine chemical reactivity and bonding.

• Types of Bonds:

  • Ionic Bonds: Transfer of electrons from one atom to another, forming ions (e.g., NaCl).

  • Covalent Bonds: Sharing of electrons between atoms.

    • Nonpolar Covalent: Equal sharing of electrons (e.g., O2).

    • Polar Covalent: Unequal sharing, resulting in partial charges (e.g., H2O).

  • Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom (important in water and DNA structure).

Chemical Reactions

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

  • General equation:

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

  • General equation:

• Exchange (Displacement): Bonds are both made and broken.

  • General equation:

• Oxidation/Reduction (Redox): Involves transfer of electrons.

  • OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).

• Factors Influencing Reaction Rate: Temperature, concentration, particle size, catalysts (enzymes).

Dehydration Synthesis vs. Hydrolysis

• Dehydration Synthesis: Removal of water to join molecules together.

• Hydrolysis: Addition of water to break bonds between molecules.

Water

• Polar Molecule: Unequal sharing of electrons creates partial charges.

• Hydrogen Bonding: Responsible for water's high heat capacity, cohesion, and solvent properties.

Salts (Ionic Compounds)

• Characteristics: Dissociate in water to form electrolytes (conduct electricity).

• Examples: NaCl, CaCO3

Acids, Bases, and the pH Scale

• Acids: Release H+ ions in solution (proton donors).

• Bases: Accept H+ ions (proton acceptors); often release OH–.

• pH Scale: Measures concentration of H+ ions.

  • pH < 7: Acidic

  • pH = 7: Neutral

  • pH > 7: Basic (alkaline)

• Interpretation: Lower pH = higher [H+], more acidic; higher pH = lower [H+], more basic.

• Neutralization Reaction: Acid + base → salt + water.

• Buffers: Resist changes in pH by accepting or donating H+ ions.

Organic Compounds

• Monomers: Small building blocks.

• Polymers: Large molecules made from monomers.

• General Characteristics: Contain carbon, covalently bonded, often large and complex.

Carbohydrates

• Function: Main source of energy for cells.

• Classes:

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

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

  • Polysaccharides: Many monosaccharides (e.g., glycogen, starch).

Lipids

• Common Characteristic: Insoluble in water, nonpolar.

• Triglycerides: Glycerol + 3 fatty acids; energy storage.

  • Saturated Fatty Acids: No double bonds; solid at room temperature.

  • Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

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

• Steroids: Four fused carbon rings; includes cholesterol, hormones (e.g., estrogen, testosterone).

Proteins

• Monomer: Amino acids (20 types).

• Levels of Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha-helix or beta-sheet (hydrogen bonding).

  • Tertiary: 3D folding of a single polypeptide chain.

  • Quaternary: Multiple polypeptide chains combined.

• Enzymes: Biological catalysts that lower activation energy.

  • Active Site: Region where substrate binds.

  • Substrate: Reactant acted upon by enzyme.

  • Denaturation: Loss of structure (and function) due to high temperature or extreme pH.

Nucleic Acids

• Monomer: Nucleotide (composed of a sugar, phosphate group, and nitrogenous base).

• Functions: Store and transmit genetic information (DNA, RNA); energy transfer (ATP).

• DNA vs. RNA:

  • DNA: Double-stranded, deoxyribose sugar, bases A-T-C-G.

  • RNA: Single-stranded, ribose sugar, bases A-U-C-G.

• ATP: Main energy currency of the cell.

Additional info: This guide expands on the review outline by providing definitions, examples, and context for each topic, ensuring a comprehensive overview suitable for exam preparation in Anatomy & Physiology.