Concepts to Know and Understand

Seven Properties of Life and Hierarchy of Organization

Biology is the study of living organisms, which share certain properties and are organized in a hierarchical manner.

• Properties of Life: Living things exhibit order, regulation, growth and development, energy processing, response to the environment, reproduction, and evolutionary adaptation.

• Hierarchy of Organization: Life is organized from the smallest to largest as follows: molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

• Example: A human is an organism, made up of organ systems, which are made of organs, and so on down to molecules.

Scientific Process: Hypotheses, Theories, and Experiments

The scientific method is a systematic approach to understanding the natural world.

• Hypothesis: A testable, falsifiable explanation for an observation.

• Theory: A broad, well-supported explanation for a wide range of phenomena.

• Controlled Experiment: An experiment in which only one variable is changed at a time.

• Variables: Independent variable (manipulated), dependent variable (measured), controlled variables (kept constant).

• Observational Data/Experiments: Data collected without manipulation, often used in field studies.

Elements, Atoms, and Compounds

All matter is composed of elements, which combine to form compounds essential for life.

• Element: A substance that cannot be broken down into simpler substances by chemical means.

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

• Atomic Number: Number of protons in an atom.

• Mass Number: Number of protons plus neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons; some are radioactive.

• Trace Elements: Elements required in very small amounts but essential for life (e.g., iron, iodine).

Chemical Bonds

Atoms combine through chemical bonds to form molecules and compounds.

• Ionic Bond: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions.

• Covalent Bond: Formed when two atoms share one or more pairs of electrons.

• How to Draw: Use Lewis dot structures to represent valence electrons and bonding.

• Unique Features: Ionic bonds create charged ions; covalent bonds create stable molecules.

Water: Properties and Importance

Water is essential for life due to its unique chemical and physical properties.

• Polarity: Water is a polar molecule, with partial positive and negative charges.

• Hydrogen Bonding: Weak bonds between the hydrogen of one water molecule and the oxygen of another.

• Cohesion and Adhesion: Cohesion is the attraction between water molecules; adhesion is attraction to other substances.

• Surface Tension: The result of cohesion at the surface of water.

• High Specific Heat and Evaporative Cooling: Water resists temperature change and cools surfaces as it evaporates.

• Solvent Properties: Water dissolves many substances, making it the "universal solvent." Equation:

Acids, Bases, and pH

Acids and bases are substances that alter the hydrogen ion concentration in solutions.

• Acid: Substance that increases the concentration of H+ ions in solution.

• Base: Substance that decreases the concentration of H+ ions (or increases OH-).

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Equation:

• Buffers: Substances that minimize changes in pH.

Organic Molecules and Functional Groups

Organic molecules are carbon-based and form the basis of life. Functional groups determine their properties.

• Hydrocarbons: Molecules consisting only of carbon and hydrogen.

• Functional Groups: Specific groups of atoms that confer characteristic properties (e.g., -OH, -COOH, -NH2, -PO42-).

• Isomers: Molecules with the same formula but different structures.

Macromolecules: Carbohydrates, Lipids, Proteins

Macromolecules are large, complex molecules essential for life. They are built from smaller subunits.

Carbohydrates

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

• Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose).

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

• Function: Energy storage and structural support.

• Dehydration Reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Lipids

• General Characteristics: Hydrophobic molecules, including fats, phospholipids, and steroids.

• Fats: Composed of glycerol and fatty acids; used for energy storage.

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

• Steroids: Lipids with a four-ring structure (e.g., cholesterol).

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

Proteins

• General Characteristics: Polymers of amino acids; perform a wide range of functions.

• Amino Acid Structure: Central carbon, amino group (-NH2), carboxyl group (-COOH), hydrogen, and R group.

• Peptide Bonds: Link amino acids to form polypeptides.

• Levels of Structure: Primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple polypeptides).

• Denaturation: Loss of protein structure and function due to environmental changes.

Table: Comparison of Macromolecules

Additional info:

• Be able to identify macromolecules by their structure and know their general functions.

• Review the differences between polar and nonpolar covalent bonds, and the significance of hydrophobic vs. hydrophilic molecules.

• Practice drawing and interpreting basic chemical structures and reactions.