Introduction to Biology

What is Life?

Biology is the study of living organisms and their vital processes. Life is characterized by a constellation of phenomena including organization, metabolism, responsiveness, growth, and reproduction.

• Order/Organization: Living things exhibit complex but ordered organization.

• Energy Processing: Organisms obtain and use energy. For example, plants convert solar energy into chemical energy via photosynthesis.

• Regulation (Homeostasis): Internal conditions are maintained within certain limits despite external changes (e.g., body temperature regulation).

• Response to the Environment: Organisms sense and respond to environmental stimuli (e.g., sweating when hot).

• Reproduction: Organisms reproduce their own kind.

• Growth and Development: Organisms grow and develop according to specific instructions coded in their genes.

• Evolutionary Adaptation: Populations evolve over generations through adaptations that enhance survival and reproduction.

Emergent Properties: New properties arise at each level of biological organization that are not present at lower levels.

Chemistry of Life

Molecules and Bonds

Molecules are the simplest units of chemical compounds. Water is the solvent of life, and its unique properties are essential for biological processes.

• Covalent Bonds: Atoms share electron pairs. Example: H2O, where electrons are shared between hydrogen and oxygen.

• Nonpolar Covalent Bonds: Electrons are shared equally (e.g., between two carbon atoms).

• Polar Covalent Bonds: Electrons are shared unequally, resulting in partial charges (e.g., in water, oxygen is more electronegative than hydrogen).

• Hydrogen Bonds: Weak attractions between the partial positive charge of one molecule and the partial negative charge of another (e.g., between water molecules).

• Ions: Atoms or molecules with a net electric charge. Ions dissolve in water due to attraction to water's partial charges.

Example: Ammonia (NH3) has a partial negative charge on nitrogen and partial positive charges on hydrogens, allowing it to form hydrogen bonds with water.

Macromolecules and Functional Groups

• Hydrocarbons: Molecules consisting only of hydrogen and carbon; energy is stored in their chemical bonds.

• Functional Groups: Specific groups of atoms (e.g., -OH, -COOH, -NH2) that confer particular chemical properties to hydrocarbons, making them more versatile.

Organic Macromolecules

Monomers and Polymers

• Monomer: A single subunit that can join with others to form a polymer.

• Polymer: A large molecule made of many monomers.

Polymerization and Breakdown

• Dehydration Synthesis: Monomers are joined by covalent bonds with the removal of water.

• Hydrolysis: Polymers are broken down into monomers by the addition of water.

• Enzymes: Biological catalysts that speed up both dehydration synthesis and hydrolysis.

Types of Macromolecules

• Carbohydrates: Sugars and polymers of sugars (e.g., starch, glycogen, cellulose, chitin).

• Proteins: Polymers of amino acids with diverse functions (enzymes, structure, transport, etc.).

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

Carbohydrates

Classification and Functions

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

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

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

Major Polysaccharides

• Starch: Energy storage in plants.

• Glycogen: Energy storage in animals, found in liver and muscle cells.

• Cellulose: Structural component of plant cell walls; indigestible by humans.

• Chitin: Structural component in fungi cell walls and exoskeletons of arthropods.

Oligosaccharides: Carbohydrates composed of a small number (3-20) of monosaccharides.

Proteins

Structure and Properties

• Monomer: Amino acid (20 types, each with a unique R group).

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

• Peptide Bond: Covalent bond linking amino acids.

• Dipeptide: Two amino acids joined by a peptide bond.

• Polypeptide: Many amino acids joined in a chain.

Protein Folding and Structure

• Primary Structure: Sequence of amino acids in a polypeptide.

• Secondary Structure: Local folding due to hydrogen bonding (e.g., alpha helix, beta pleated sheet).

• Tertiary Structure: Overall 3D shape due to interactions among R groups.

• Quaternary Structure: Association of multiple polypeptide chains.

Hydrophilic R Groups: Polar or charged, interact with water. Hydrophobic R Groups: Nonpolar, avoid water.

Classification of Living Organisms

Domains and Kingdoms

• Bacteria and Archaea: Prokaryotic cells (no nucleus).

• Eukaryotes: Cells with a nucleus, divided into four kingdoms: Protista, Animalia, Fungi, Plantae.

Characteristics of Animals (Eukaryotic)

• Multicellular

• Heterotrophic (ingest food)

• Lack cell wall

• Cells organized into tissues

• Motility/mobility

• Specific development patterns/genes

Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells: Simple, lack a nucleus and membrane-bound organelles. Example: Bacteria, Archaea.

• Eukaryotic Cells: Have a nucleus and specialized organelles. Example: Plants, animals, fungi, protists.

Key Cell Components

• Cell Membrane: Lipid bilayer that controls movement of substances in and out of the cell.

• Nucleus: Contains genetic material (DNA).

• Mitochondria: Site of ATP (energy) production via cellular respiration.

• Chloroplasts: (In plants) Site of photosynthesis.

• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.

• Golgi Apparatus: Modifies, sorts, and packages proteins for secretion.

Cell Function

• Metabolism

• Energy conversion

• Response to environmental signals

• Reproduction (mitosis and meiosis)

Summary Table: Major Macromolecules

Key Equations

• Dehydration Synthesis:

• Hydrolysis:

Additional info: This study guide expands on the provided notes with definitions, examples, and a summary table for clarity and completeness.