Atoms and Atomic Structure

Levels of Organization in Humans

The human body is organized into hierarchical levels, each with distinct structural and functional properties. Understanding these levels is fundamental to anatomy and physiology.

• Key Point 1: The major levels of organization are: chemical, cellular, tissue, organ, organ system, and organism.

• Key Point 2: Each level builds upon the previous, increasing in complexity and specialization.

• Example: Muscle tissue (tissue level) is composed of muscle cells (cellular level) and contributes to the muscular system (organ system level).

Definitions: Matter, Element, Atom, Molecule

Basic chemical concepts are essential for understanding biological processes.

• Matter: Anything that has mass and occupies space.

• Element: A pure substance consisting of only one type of atom; cannot be broken down by chemical means.

• Atom: The smallest unit of an element, composed of protons, neutrons, and electrons.

• Molecule: Two or more atoms chemically bonded together.

• Example: Water (H2O) is a molecule made of hydrogen and oxygen atoms.

Common Elements in the Human Body

Most of the human body is composed of a few key elements, each with specific chemical properties.

• Key Point 1: The most common elements are oxygen, carbon, hydrogen, and nitrogen (constituting about 96% of body mass).

• Key Point 2: Trace elements (e.g., iron, iodine) are present in small amounts but are essential for health.

• Example: Iron is a trace element necessary for hemoglobin function.

Atomic Structure

Atoms consist of subatomic particles arranged in specific ways, determining their chemical behavior.

• Key Point 1: Subatomic particles include protons (positive charge), neutrons (neutral), and electrons (negative charge).

• Key Point 2: The atomic number equals the number of protons; the mass number equals protons plus neutrons.

• Key Point 3: Electrons occupy energy shells; the first shell holds up to 2 electrons, the second up to 8.

• Example: Carbon (C) has 6 protons, 6 neutrons, and 6 electrons.

Metric System

Measurement in Science

The metric system is used for scientific measurements due to its consistency and ease of conversion.

• Key Point 1: Common metric units include meter (length), liter (volume), gram (weight), and Celsius (temperature).

• Key Point 2: Prefixes such as kilo-, centi-, milli-, and micro- indicate multiples or fractions of base units.

• Example: 1 kilometer = 1000 meters; 1 milliliter = 0.001 liters.

Temperature Conversion

• Key Point: Water freezes at 0°C and boils at 100°C.

• Formula:

• Example: 25°C = 77°F

Chemical Reactions and Bonds

Molecules and Compounds

Molecules and compounds are formed by chemical bonds between atoms.

• Molecule: Two or more atoms bonded together (can be same or different elements).

• Compound: A molecule containing atoms of different elements.

• Example: Oxygen gas (O2) is a molecule; water (H2O) is a compound.

Chemical Reactions

Chemical reactions involve the making and breaking of bonds, resulting in new substances.

• Key Point 1: Reactants are transformed into products.

• Key Point 2: Factors affecting reaction rate include temperature, concentration, and catalysts.

• Example: Cellular respiration is a chemical reaction converting glucose and oxygen into carbon dioxide and water.

Chemical Bonds

Bonds hold atoms together in molecules and compounds, with different types affecting properties.

• Ionic Bonds: Formed by transfer of electrons between atoms, creating charged ions.

• Covalent Bonds: Formed by sharing electrons between atoms.

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

• Example: Sodium chloride (NaCl) is held together by ionic bonds; water molecules are attracted by hydrogen bonds.

Lewis Dot Structures and Electronegativity

Lewis dot structures represent valence electrons and help predict bonding behavior.

• Key Point: Electronegativity is the tendency of an atom to attract electrons in a bond.

• Example: Oxygen is more electronegative than hydrogen, leading to polar covalent bonds in water.

Water Modeling – Properties of Water

Intermolecular Bonds in Water

Water's unique properties arise from hydrogen bonding between molecules.

• Key Point 1: Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another.

• Key Point 2: These bonds give water high cohesion, adhesion, surface tension, and heat capacity.

• Example: Water beads on a surface due to surface tension.

Phases of Water

• Key Point: Water exists as solid (ice), liquid, and gas (vapor), with hydrogen bonds affecting each phase.

• Example: Ice floats because hydrogen bonds hold water molecules apart, making ice less dense than liquid water.

Classes of Compounds, pH, and Introduction to Organic Chemistry

Organic vs. Inorganic Compounds

Compounds in the body are classified as organic (carbon-based) or inorganic.

• Organic Compounds: Contain carbon and hydrogen; include carbohydrates, lipids, proteins, and nucleic acids.

• Inorganic Compounds: Do not contain both carbon and hydrogen; include water, salts, acids, and bases.

• Example: Glucose is organic; sodium chloride is inorganic.

pH, Acids, and Bases

pH measures the concentration of hydrogen ions in a solution, indicating acidity or alkalinity.

• Definition:

• Acid: Substance that increases H+ concentration; pH < 7.

• Base: Substance that decreases H+ concentration; pH > 7.

• Buffer: Solution that resists changes in pH.

• Example: Blood has a pH of about 7.4 (slightly basic).

Valence Electrons and Functional Groups

Valence electrons determine bonding capacity; functional groups confer specific chemical properties.

• Key Point 1: Carbon has 4 valence electrons and can form up to 4 covalent bonds.

• Key Point 2: Common functional groups include hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and phosphate (-PO4).

• Example: The carboxyl group is found in amino acids.

Organic Compounds: Carbohydrates, Lipids, and Proteins

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, serving as energy sources and structural components.

• Atoms: C, H, O

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

• Categories: Monosaccharides (one sugar), disaccharides (two sugars), polysaccharides (many sugars)

• Functions: Energy storage (glycogen in humans, starch in plants), structural support (cellulose in plants)

• Example: Sucrose is a disaccharide; glycogen is a polysaccharide stored in the liver.

Lipids

Lipids are hydrophobic organic molecules, including fats, phospholipids, and steroids.

• Atoms: Mostly C, H, O

• Types: Triglycerides, phospholipids, steroids

• Properties: Insoluble in water; nonpolar

• Functions: Energy storage, cell membrane structure, hormone production

• Example: Phospholipids form the bilayer of cell membranes.

Proteins

Proteins are polymers of amino acids, performing diverse functions in the body.

• Atoms: C, H, O, N, (sometimes S)

• Monomer: Amino acid

• Functions: Enzymes, structural support, transport, signaling

• Example: Hemoglobin transports oxygen in blood.

HTML Table: Comparison of Bond Types

HTML Table: Common Functional Groups

Additional info: Academic context and examples have been added to clarify and expand upon the original question prompts, ensuring the notes are self-contained and suitable for exam preparation.