General Biology Exam 1 Study Guide: Core Concepts and Molecular Foundations

Themes in the Study of Life

Organization and Diversity of Life

The study of biology begins with understanding the diversity and organization of living systems. Life is classified into major domains and kingdoms, each with unique characteristics.

• Eukaryotes vs. Prokaryotes: Prokaryotes are unicellular organisms lacking a nucleus (e.g., Bacteria, Archaea). Eukaryotes possess a nucleus and membrane-bound organelles (e.g., Plants, Animals, Fungi).

• Order of Organization: Biological systems are organized hierarchically: atoms → molecules → organelles → cells → tissues → organs → organisms → populations → communities → ecosystems → biosphere.

• Evolution and Natural Selection: Evolution is the process by which populations change over time through natural selection, where advantageous traits become more common.

• Unity and Diversity: All living organisms share fundamental molecular and genetic features (e.g., DNA structure), yet exhibit vast diversity in form and function.

• Scientific Method: Steps include observation, hypothesis formation, experimentation, data analysis, and conclusion.

The Chemical Context of Life

Elements and Atomic Structure

Life is composed primarily of a few key elements and their interactions form the basis of biological molecules.

• Essential Elements: Four elements—carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)—make up about 96% of living matter.

• Atomic Structure: Atoms consist of protons (positive charge), neutrons (neutral), and electrons (negative charge). Atomic number is the number of protons; atomic mass is the sum of protons and neutrons.

Chemical Bonds

Atoms interact through chemical bonds to form molecules essential for life.

• Covalent Bonds: Atoms share electrons. Nonpolar covalent bond: electrons shared equally. Polar covalent bond: electrons shared unequally, creating partial charges.

• Hydrogen Bonds: Weak attractions between a hydrogen atom (partially positive) and an electronegative atom (e.g., oxygen or nitrogen).

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions.

Water and the Fitness of the Environment

Properties of Water

Water's unique properties make it essential for life and biological processes.

• Charges of Water Molecule: Water (H2O) is polar, with partial negative charge near oxygen and partial positive charge near hydrogens.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Surface Tension: Cohesion at the surface allows water to resist external force.

• Adhesion: Water molecules stick to other substances.

• pH: Measures hydrogen ion concentration. $\text{pH} = -\log_{10}[\text{H}^+]$

• Bonding: Hydrogen bonding is responsible for water's high specific heat, solvent properties, and ice formation.

Carbon and the Molecular Diversity of Life

Carbon's Role in Biological Molecules

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds.

• Carbon Dioxide and Acidification: CO2 dissolves in water, forming carbonic acid, which can lower pH and affect marine life.

• Carbon's Importance: Carbon forms the skeleton of all organic molecules, enabling complex structures.

Isomers and Functional Groups

• Isomers: Molecules with the same molecular formula but different structures. Types: Enantiomers: Mirror-image isomers. Cis-trans isomers: Differ in spatial arrangement around double bonds. Structural isomers: Differ in covalent arrangement of atoms.

• Functional Groups: Groups of atoms that confer specific chemical properties. Examples: Carboxyl group (-COOH): Acidic properties. Carbonyl group (C=O): Found in sugars.

Monomers and Polymers

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

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

The Structure and Function of Large Biological Molecules

Major Biological Polymers

Biological macromolecules are essential for structure, function, and regulation of the body's tissues and organs.

Polymer	Monomer	Main Function
Carbohydrates	Monosaccharides	Energy storage, structural support
Proteins	Amino acids	Catalysis (enzymes), structure, transport, signaling
Lipids	Fatty acids, glycerol	Energy storage, membrane structure, signaling
Nucleic Acids	Nucleotides	Genetic information storage and transfer

• Carbohydrates: Provide energy and structural support (e.g., cellulose in plants).

• Proteins: Made of amino acids; perform diverse functions including catalysis (enzymes), transport, and signaling.

• Lipids: Include fats, oils, and phospholipids; important for energy storage and cell membranes.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

Additional info: Academic context and definitions have been expanded for clarity and completeness.