General Biology Study Guide: Foundations of Life, Chemistry, Biological Molecules, and Cell Structure

Chapter 1: Introduction to Life on Earth

Characteristics and Organization of Life

This section introduces the fundamental properties that define living organisms and the hierarchical organization of life on Earth.

• Biology: The scientific study of living organisms and their processes.

• 7 Characteristics of Life:

  1. Order (organized structure)

  2. Acquire and use energy

  3. Homeostasis (maintaining internal balance)

  4. Respond to stimuli

  5. Growth

  6. Reproduction (DNA as hereditary material)

  7. Evolution (adaptation over generations)

• Levels of Organization (from smallest to largest):

  1. Atoms

  2. Molecules

  3. Organelles

  4. Cells

  5. Tissues

  6. Organs

  7. Organ systems

  8. Organisms

  9. Populations

  10. Communities

  11. Ecosystems

  12. Biosphere

• Autotrophs vs. Heterotrophs:

  • Autotrophs: Organisms that produce their own food (e.g., plants via photosynthesis).

  • Heterotrophs: Organisms that obtain food by consuming other organisms (e.g., animals).

• Homeostasis: The maintenance of stable internal conditions despite external changes.

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

• Domains of Life: Bacteria, Archaea, Eukarya.

• Binomial Nomenclature: The two-part scientific naming system for organisms (e.g., Homo sapiens).

• Scientific Method: A systematic approach to inquiry involving observation, hypothesis, experimentation, and theory development.

Example: Humans are heterotrophic, multicellular eukaryotes that maintain homeostasis and reproduce sexually.

Chapter 2: Atoms, Molecules, and Life

Basic Chemistry for Biology

This section covers the chemical principles essential for understanding biological processes, including atomic structure, chemical bonds, and water's properties.

• Atoms: The smallest units of matter, composed of protons, neutrons, and electrons.

• Subatomic Particles:

  • Protons: Positively charged, in nucleus

  • Neutrons: Neutral, in nucleus

  • Electrons: Negatively charged, orbit nucleus

• Elements and Isotopes:

  • Element: Substance made of one type of atom

  • Isotope: Atoms of the same element with different numbers of neutrons

• Chemical Bonds:

  • Ionic Bonds: Transfer of electrons between atoms (e.g., NaCl)

  • Covalent Bonds: Sharing of electrons (e.g., H2O)

  • Hydrogen Bonds: Weak attractions between polar molecules (e.g., between water molecules)

• Properties of Water:

  • Cohesion and adhesion

  • Surface tension

  • High specific heat

  • Solvent ability

  • Ice floats (less dense than liquid water)

• Acids, Bases, and Buffers:

  • Acid: Releases H+ ions in solution

  • Base: Accepts H+ ions or releases OH-

  • Buffer: Substance that minimizes pH changes

Example: Water's high specific heat helps organisms maintain stable internal temperatures.

Formula:

$\text{pH} = -\log_{10}[\text{H}^+]$

Chapter 3: Biological Molecules

Macromolecules and Their Functions

This section explores the four major classes of biological macromolecules, their structures, and their roles in living organisms.

• Organic Molecules: Carbon-based compounds found in living things.

• Functional Groups: Specific groups of atoms (e.g., hydroxyl, carboxyl, amino, phosphate) that confer properties to molecules.

• Dehydration Synthesis: Reaction that joins monomers by removing water.

• Hydrolysis: Reaction that breaks polymers into monomers by adding water.

• Macromolecules:

  • Carbohydrates: Energy storage and structure (monomer: monosaccharide)

  • Lipids: Energy storage, membranes, signaling (monomer: fatty acid/glycerol)

  • Proteins: Structure, enzymes, transport (monomer: amino acid)

  • Nucleic Acids: Genetic information (monomer: nucleotide)

• Levels of Protein Structure:

  1. Primary: Amino acid sequence

  2. Secondary: Alpha helices and beta sheets

  3. Tertiary: 3D folding

  4. Quaternary: Multiple polypeptides

• ATP (Adenosine Triphosphate): The main energy currency of the cell.

Example: Starch and glycogen are storage polysaccharides; cellulose and chitin are structural polysaccharides.

Chapter 4: Cell Structure and Function

Cell Types, Organelles, and Cellular Organization

This section describes the structure and function of cells, the differences between prokaryotic and eukaryotic cells, and the roles of various organelles.

• Cell: The smallest unit of life.

• Prokaryotes vs. Eukaryotes:

  • Prokaryotes: No nucleus, simple structure (e.g., bacteria, archaea)

  • Eukaryotes: Nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists)

• Plasma Membrane: Phospholipid bilayer that controls entry and exit of substances.

• Organelles:

  • Nucleus: Contains DNA

  • Ribosomes: Protein synthesis

  • Mitochondria: "Powerhouse" of the cell, site of cellular respiration

  • Chloroplasts: Photosynthesis (plants and algae)

  • Endoplasmic Reticulum (ER): Protein and lipid synthesis

  • Golgi Apparatus: Modifies and packages proteins

  • Lysosomes: Digestion of macromolecules

  • Vacuoles: Storage

  • Cytoskeleton: Structural support and movement

• Endomembrane System: Network of membranes involved in transport within the cell.

• Pathway of Protein Secretion: DNA → mRNA → Ribosome → ER → Golgi → Vesicle → Plasma membrane.

• Plasmids: Small, circular DNA in prokaryotes.

• Compartmentalization: Division of eukaryotic cells into organelles for specialized functions.

Example: Mitochondria and chloroplasts have their own DNA and ribosomes, supporting the endosymbiotic theory.

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
DNA Location	Nucleoid region	Nucleus
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists