General Biology: Core Concepts and Foundations Study Guide

Five Unifying Themes of Biology

Overview of Biological Themes

• Core Theme: Evolution is the central, unifying concept that explains the unity and diversity of life.

• Emergent Properties: New properties arise at each level of biological organization that are not present at the preceding level.

• Levels of Biological Organization: Ranges from molecules to the biosphere, including cells, tissues, organs, organisms, populations, communities, ecosystems, and the biosphere.

Genetics and Gene Expression

Gene Expression

• Definition: The process by which information from a gene is used to synthesize a functional gene product, usually a protein.

• Central Dogma: DNA → RNA → Protein

Scientific Method and Experimental Design

Experiments and Variables

• Predictions and Hypotheses: Hypotheses are testable statements; predictions are specific outcomes expected if the hypothesis is true.

• Control Variables: Variables kept constant to ensure a fair test.

• Independent Variable: The variable that is changed or controlled in a scientific experiment.

• Dependent Variable: The variable being tested and measured.

Theories vs. Hypotheses

• Theory: A broad, well-substantiated explanation of some aspect of the natural world.

• Hypothesis: A specific, testable prediction.

Chemistry of Life

Atoms, Elements, and Compounds

• Atoms: The smallest unit of matter that retains the properties of an element.

• Elements: Substances that cannot be broken down into other substances by chemical means.

• Compounds: Substances formed from two or more elements in fixed ratios.

Subatomic Particles

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Atomic Number and Mass Number

• Atomic Number: Number of protons in an atom.

• Mass Number: Sum of protons and neutrons.

Periodic Table and Valence Electrons

• Periodic Table: Organizes elements by increasing atomic number and recurring chemical properties.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Chemical Bonds and Water

Types of Chemical Bonds

• Covalent Bonds: Atoms share electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

• Ionic Bonds: Transfer of electrons from one atom to another, creating charged ions.

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

Properties of Water

• Cohesion and Adhesion: Water molecules stick to each other and to other substances.

• High Specific Heat: Water can absorb a lot of heat before changing temperature.

• Solvent Properties: Water dissolves many substances due to its polarity.

Acids, Bases, and pH

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

• Base: Substance that reduces H+ concentration.

• pH Scale: Measures acidity or basicity; ranges from 0 (acidic) to 14 (basic).

Significance of Stanley-Miller Experiment

• Demonstrated that organic molecules could be synthesized abiotically under early Earth conditions.

Organic Molecules and Isomerism

Organic Molecules and Carbon Bonds

• Organic Molecules: Molecules containing carbon, often complex and diverse.

• Isomers: Compounds with the same molecular formula but different structures.

• Types of Isomers: Structural, cis-trans (geometric), and enantiomers (mirror images).

Macromolecules

Classes of Biological Molecules

• Carbohydrates: Sugars and polymers of sugars; energy storage and structural roles.

• Lipids: Fats, oils, phospholipids, steroids; energy storage, membrane structure.

• Proteins: Polymers of amino acids; diverse functions including enzymes, structure, transport.

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

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Saturated vs. Unsaturated Fats

• Saturated Fats: No double bonds; solid at room temperature.

• Unsaturated Fats: One or more double bonds; liquid at room temperature.

Protein Structure

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (α-helix, β-sheet).

• Tertiary Structure: 3D shape of a polypeptide.

• Quaternary Structure: Association of multiple polypeptides.

DNA vs. RNA

• DNA: Double-stranded, deoxyribose sugar, stores genetic information.

• RNA: Single-stranded, ribose sugar, involved in protein synthesis.

Cell Structure and Function

Cell Membrane Structure

• Fluid Mosaic Model: Membrane is a fluid structure with proteins embedded in or attached to a double layer of phospholipids.

• Hydrophobic vs. Hydrophilic: Hydrophobic molecules repel water; hydrophilic molecules attract water.

Membrane Transport

• Passive Transport: Movement of substances down their concentration gradient (diffusion, osmosis, facilitated diffusion).

• Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP).

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Tonicity: The ability of a solution to cause a cell to gain or lose water (isotonic, hypotonic, hypertonic).

Bulk Transport

• Exocytosis: Export of materials out of the cell by vesicle fusion with the membrane.

• Endocytosis: Import of materials into the cell by vesicle formation.

Cell Types and Organelles

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria).

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

Organelle Structure and Function

• Nucleus: Contains genetic material.

• Mitochondria: Site of cellular respiration.

• Chloroplasts: Site of photosynthesis (plants and algae).

• Endoplasmic Reticulum: Protein and lipid synthesis.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Digestion and waste removal.

Plant vs. Animal Cells

• Plant Cells: Have cell walls, chloroplasts, and large central vacuoles.

• Animal Cells: Lack cell walls and chloroplasts, have smaller vacuoles.

Endosymbiont Theory

Origin of Eukaryotic Organelles

• Endosymbiont Theory: Proposes that mitochondria and chloroplasts originated as free-living prokaryotes that were engulfed by ancestral eukaryotic cells.

• Evidence: Double membranes, their own DNA, and similarities to prokaryotes.

Summary Table: Key Differences Between Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists