Atoms and Atomic Structure

Levels of Organization in Humans

The human body is organized into a hierarchy of structural levels, from the simplest to the most complex. Understanding these levels is fundamental to the study of anatomy and physiology.

• Chemical Level: Atoms and molecules (e.g., water, glucose)

• Cellular Level: Cells, the basic unit of life (e.g., muscle cell)

• Tissue Level: Groups of similar cells (e.g., muscle tissue)

• Organ Level: Structures composed of two or more tissue types (e.g., heart)

• Organ System Level: Groups of organs working together (e.g., circulatory system)

• Organismal Level: The complete living being (e.g., a human)

Key Definitions

• Matter: Anything that has mass and occupies space.

• Element: A pure substance consisting of one type of atom (e.g., oxygen, carbon).

• Atom: The smallest unit of an element that retains its properties.

• Molecule: Two or more atoms chemically bonded together (e.g., H2O).

Elements in the Human Body

The human body is primarily composed of a few key elements:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

• Calcium (Ca)

• Phosphorus (P)

These elements make up about 96% of body mass. Trace elements (e.g., iron, iodine, zinc) are required in small amounts for vital functions.

Atomic Structure

• Subatomic Particles: Protons (positive, in nucleus), neutrons (neutral, in nucleus), electrons (negative, in electron shells).

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons.

• Electron Shells: Electrons occupy energy levels around the nucleus; the arrangement determines chemical reactivity.

• Isotopes: Atoms of the same element with different numbers of neutrons. Radioactive isotopes are unstable and emit radiation; used in medical imaging and cancer treatment.

• Octet Rule: Atoms are stable when their outermost electron shell is full (usually 8 electrons).

Metric System Lab

Measurement in Science

Accurate measurement is essential in anatomy and physiology labs. The metric system is used for consistency and precision.

• Volume: Measured in liters (L) or milliliters (mL)

• Weight: Measured in grams (g) or kilograms (kg)

• Length: Measured in meters (m), centimeters (cm), or millimeters (mm)

• Temperature: Measured in degrees Celsius (°C)

Laboratory equipment includes graduated cylinders (volume), balances (weight), rulers (length), and thermometers (temperature). Graduated cylinders provide the most precise volume measurements.

Metric Conversions

• Common prefixes: kilo- (1000), centi- (0.01), milli- (0.001), micro- (0.000001)

• To convert Celsius to Fahrenheit:

• Water freezes at 0°C (32°F) and boils at 100°C (212°F).

Graphing

Variables and Data Representation

• Independent Variable: The variable that is changed or controlled (plotted on the x-axis).

• Dependent Variable: The variable being tested or measured (plotted on the y-axis).

• Accurate graphing requires labeling axes, using appropriate scales, and plotting data points clearly.

Chemical Reactions and Bonds

Molecules vs. Compounds

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

• Compound: A molecule containing two or more different elements (e.g., H2O).

Chemical Bonds

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

• Covalent Bonds: Sharing of electrons between atoms (e.g., H2O).

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and biological molecules.

• Ions: Charged atoms or molecules (cations: positive, anions: negative).

• Electronegativity: The tendency of an atom to attract electrons in a bond.

Lewis Dot Structures and the Octet Rule

• Lewis dot structures represent valence electrons as dots around atomic symbols.

• The Octet Rule helps predict atom stability: atoms tend to gain, lose, or share electrons to achieve 8 in their outer shell.

Chemical Reactions

• Reactants are transformed into products.

• Factors affecting reaction rate: temperature, concentration, catalysts, and surface area.

Importance of Water and pH

Properties of Water

• Solvent: Dissolves many substances, facilitating chemical reactions.

• Hydrophilic vs. Hydrophobic: Hydrophilic substances dissolve in water; hydrophobic do not.

• Cohesion: Water molecules stick together (surface tension).

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water resists temperature change.

• High Heat of Vaporization: Requires much energy to evaporate.

• Lower Density as a Solid: Ice floats on water.

pH and Buffers

• pH: Measures hydrogen ion concentration; scale from 0 (acidic) to 14 (basic), 7 is neutral.

• Acid: Substance that increases H+ concentration.

• Base: Substance that decreases H+ concentration.

• Buffers: Substances that minimize changes in pH.

• Average pH of human blood: 7.4 (slightly basic).

Water Modeling – Examining Properties of Water Lab

• Hydrogen Bonds: Hold water molecules together, responsible for cohesion and surface tension.

• Phases of Water: Solid (ice), liquid (water), gas (vapor); hydrogen bonding affects phase transitions.

• Polar Covalent Bonds: Within water molecules, create partial charges that allow hydrogen bonding.

Classes of Compounds and Introduction to Organic Chemistry

Inorganic vs. Organic Compounds

• Inorganic Compounds: Do not contain both carbon and hydrogen (e.g., water, salts, acids, bases).

• Organic Compounds: Contain carbon and hydrogen (e.g., carbohydrates, lipids, proteins, nucleic acids).

Bonding in Organic Compounds

• Covalent Bonds: Present in all organic compounds; carbon forms four covalent bonds to be stable.

• Valence Electrons: Carbon has 4; forms 4 bonds.

Functional Groups

• Specific groups of atoms that confer characteristic properties (e.g., hydroxyl, carboxyl, amino, phosphate).

• Important for the structure and function of organic molecules.

Monomers and Polymers

• Monomer: Small building block molecule (e.g., glucose).

• Polymer: Large molecule made of repeating monomers (e.g., starch).

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Building Molecules with Molecular Models Lab

• Identify and name hydrocarbons (up to 10 carbons) by model, molecular, or structural formula.

• Recognize functional groups and name molecules containing them.

• Calculate molecular weight from molecular or structural formula.

Carbohydrates, Lipids, and Proteins

Carbohydrates

• Atoms: Carbon, hydrogen, oxygen (C:H:O ratio ~1:2:1).

• Monomer: Monosaccharide (e.g., glucose).

• Categories: Monosaccharides, disaccharides, polysaccharides.

• Isomers: Molecules with the same formula but different structures (e.g., glucose and fructose).

• Functions: Energy source, storage (glycogen in animals, starch in plants), structure (cellulose in plant cell walls).

Lipids

• Atoms: Carbon, hydrogen, oxygen (less oxygen than carbohydrates).

• Types: Triglycerides, phospholipids, steroids.

• Hydrophobic: Lipids do not dissolve in water.

• Building Blocks: Fatty acids and glycerol (triglycerides); phosphate group (phospholipids).

• Saturated vs. Unsaturated: Saturated fats have no double bonds; unsaturated have one or more.

• Functions: Energy storage, insulation, protection, cell membrane structure, hormones (steroids).

Proteins

• Atoms: Carbon, hydrogen, oxygen, nitrogen (sometimes sulfur).

• Monomer: Amino acid (20 different types).

• Structure: Four levels—primary (amino acid sequence), secondary (alpha helices, beta sheets), tertiary (3D folding), quaternary (multiple polypeptides).

• Denaturation: Loss of protein shape due to heat or pH changes.

• Functions: Enzymes, structure, transport, defense, signaling.

Enzyme Lab

• Catalyst: Substance that speeds up a chemical reaction without being consumed.

• Enzyme: Biological catalyst, usually a protein.

• Substrate: The reactant on which an enzyme acts.

• Active Site: Region of enzyme where substrate binds.

• Factors Affecting Enzyme Activity: pH, temperature, substrate concentration.

• Optimal Conditions: Each enzyme has a specific pH and temperature at which it works best.

• Denaturation: Extreme pH or temperature can alter enzyme shape and function.

Root Words 1-18

• Know the meaning and an example of a word containing each root (e.g., 'cardio' means heart, as in 'cardiology').

*Additional info: Some explanations and examples were expanded for clarity and completeness based on standard Anatomy & Physiology curricula.*