General Biology Study Guide: Themes, Chemistry, Cells, and Membranes

Chapter 1: Themes in the Study of Life

Basic Properties of Life

The study of biology begins with understanding the fundamental characteristics that define living organisms.

• Order: Living things exhibit complex organization.

• Regulation: Organisms maintain stable internal environments (homeostasis).

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Energy Processing: Living things acquire and use energy.

• Response to Environment: Organisms respond to stimuli.

• Reproduction: Living things produce offspring.

• Evolutionary Adaptation: Populations evolve over generations.

Levels of Biological Organization

Biological systems are organized in a hierarchy from smallest to largest.

• Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Structure and Function Correlation

Biological structures are closely related to their functions. For example, the shape of a bird's wing enables flight.

The Scientific Process

• Observation → Question → Hypothesis → Experiment → Analysis → Conclusion

• Hypothesis: A testable explanation for an observation.

• Theory: A broader, well-supported explanation of natural phenomena.

Chapters 2 & 3: General Chemistry & Water

Basic Structure of Atoms

Atoms are the fundamental units of matter, composed of protons, neutrons, and electrons.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Sum of protons and neutrons.

• Atomic Mass: Weighted average mass of an atom.

Chemical Bonds

Atoms interact to form molecules through various types of chemical bonds.

• Covalent Bonds: Atoms share electrons.

• Ionic Bonds: Atoms transfer electrons, forming charged ions.

• Hydrogen Bonds: Weak attractions between polar molecules.

Biologically Important Elements

• Major Elements: Hydrogen (H), Oxygen (O), Nitrogen (N), Carbon (C)

Chemical and Physical Properties of Water

Water is essential for life due to its unique properties.

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

• High Specific Heat: Water resists temperature changes.

• Solvent Properties: Water dissolves many substances.

• Density of Ice: Ice is less dense than liquid water.

pH Scale and Buffers

The pH scale measures the concentration of hydrogen ions in a solution.

• pH Scale: Ranges from 0 (acidic) to 14 (basic); 7 is neutral.

• pOH: Measures hydroxide ion concentration.

• Buffers: Substances that minimize changes in pH.

Formula:

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

Chapters 4 & 5: Organic Chemistry & Large Biological Molecules

Functional Groups

Functional groups are specific groups of atoms within molecules that determine chemical properties.

• Hydroxyl (-OH)

• Carbonyl (C=O)

• Carboxyl (-COOH)

• Amino (-NH2)

• Sulfhydryl (-SH)

• Phosphate (-PO4)

• Methyl (-CH3)

Macromolecules

Large biological molecules are essential for structure and function in living organisms.

• Carbohydrates: Energy storage and structural support.

• Lipids: Energy storage, membrane structure.

• Proteins: Catalysis, structure, transport.

• Nucleic Acids: Genetic information storage and transfer.

Chapter 6: Cell Structure and Functions

Prokaryotic vs. Eukaryotic Cells

Cells are classified based on the presence or absence of a nucleus and membrane-bound organelles.

• Prokaryotic Cells: No nucleus, no membrane-bound organelles (e.g., bacteria).

• Eukaryotic Cells: Nucleus and organelles (e.g., plants, animals, fungi).

Functions of Eukaryotic Cell Parts

Eukaryotic cells contain specialized structures for various functions.

• Cell Wall: Structural support (plants, fungi).

• Cell Membrane: Controls entry/exit of substances.

• Nucleus: Contains genetic material.

• Nucleolus: Ribosome synthesis.

• Cytoplasm: Site of metabolic activity.

• Ribosomes: Protein synthesis.

• Endoplasmic Reticulum (Rough/Smooth): Protein and lipid synthesis.

• Vacuoles: Storage and waste disposal.

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

• Lysosomes: Digestion of macromolecules.

• Peroxisomes: Breakdown of fatty acids.

• Mitochondria: ATP production.

• Chloroplasts: Photosynthesis (plants).

• Cilia and Flagella: Movement.

• Plasmodesmata: Cell communication (plants).

• Intercellular Junctions: Cell-to-cell connections.

• ECM (Extracellular Matrix): Support and signaling (animals).

Plant vs. Animal Cells

Feature	Plant Cells	Animal Cells
Cell Wall	Present	Absent
Plastids (e.g., chloroplasts)	Present	Absent
Central Vacuole	Large, central	Small or absent
ECM	Absent	Present

Microscopy Techniques

• Light Microscopy: Uses visible light to observe cells.

• Electron Microscopy: Uses electrons for higher resolution; includes scanning and transmission types.

Chapter 7: Membrane Structure and Function

Cell Membranes

Cell membranes are composed of a phospholipid bilayer with embedded proteins, controlling the movement of substances.

• Phospholipid Bilayer: Hydrophilic heads and hydrophobic tails.

• Proteins: Transport, signaling, structural support.

Osmosis and Tonicity

Osmosis is the movement of water across membranes; tonicity describes the effect of solute concentration on cells.

• Hypertonic: Higher solute concentration outside the cell; cell shrinks.

• Hypotonic: Lower solute concentration outside; cell swells.

• Isotonic: Equal solute concentration; no net water movement.

Transport Mechanisms

Cells use various mechanisms to move substances across membranes.

• Diffusion: Movement from high to low concentration.

• Osmosis: Diffusion of water.

• Facilitated Diffusion: Transport via membrane proteins.

• Active Transport: Movement against concentration gradient; requires energy.

• Endocytosis/Exocytosis: Bulk transport into/out of the cell.

Formula:

$\text{Rate of diffusion} \propto \frac{\text{Surface Area} \times \text{Concentration Difference}}{\text{Distance}}$

Additional info: These notes are expanded from a syllabus outline and include academic context for clarity and completeness.