General Biology Chapters 1–4: Comprehensive Study Notes with Diagrams

Chapter 1: The Themes of Biology and the Scientific Method

Key Concepts

Biology is the scientific study of life, encompassing the regulation, growth, development, energy processing, response to stimuli, reproduction, and evolutionary adaptation of living organisms.

• Levels of Organization: Biological systems are organized hierarchically from the smallest to largest units.

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

• Emergent Properties: New traits appear as complexity increases.

• Structure–Function Relationship: Biological structures are shaped to perform specific functions (e.g., enzymes fit specific substrates).

• Information Flow: DNA → RNA → Protein → Trait.

• Energy and Matter: Energy flows; matter cycles.

• Evolution: The unifying principle of biology, explaining both unity and diversity of life.

Scientific Method Diagram

The scientific method is a systematic approach to investigation and discovery in biology.

• Steps: Observation → Question → Hypothesis → Prediction → Experiment → Analysis → Conclusion → Share

• Variables:

  • Independent: Manipulated variable

  • Dependent: Measured variable

  • Control: Baseline for comparison

  • Constants: Factors kept unchanged

Must Know

• Define life’s characteristics.

• Describe levels of organization.

• Explain evolution’s role in unity and diversity.

Chapter 2: The Chemical Basis of Life

Atomic Structure

Atoms are the basic units of matter, composed of protons, neutrons (in the nucleus), and electrons (orbiting in shells).

p⁺ n⁰ (Nucleus) Electrons (–) orbit in shells

Bonds Overview

Chemical bonds form between atoms to create molecules. The main types are:

Bond Type	Description	Example
Covalent	Shared electrons	H₂O, CH₄
Ionic	Electron transfer	NaCl
Hydrogen	Attraction between polar molecules	Between H₂O molecules

Water’s Unique Properties

Water is essential for life due to its unique chemical and physical properties, largely resulting from hydrogen bonding.

δ– O —— H δ+ | H δ+ —— O δ–

Property	Description	Biological Role
Cohesion	Water sticks to itself	Surface tension, plant transport
Adhesion	Water sticks to other surfaces	Capillary action
High specific heat	Resists temperature change	Stabilizes body temp
Ice floats	Solid less dense	Aquatic life survives winter
Solvent	Dissolves polar/ionic compounds	Enables reactions in cells

pH Scale

The pH scale measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• Acidic: pH < 7

• Neutral: pH = 7

• Basic: pH > 7

Chapter 3: The Molecules of Cells

Functional Groups Overview

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

Group	Structure	Function
Hydroxyl	–OH	Polar; alcohols
Carboxyl	–COOH	Acidic; fatty acids, proteins
Amino	–NH₂	Basic; amino acids
Phosphate	–PO₄	Energy transfer (ATP)
Methyl	–CH₃	Gene expression

Building and Breaking Polymers

Polymers are large molecules made by joining monomers. Two key reactions are:

• Dehydration: Monomer + Monomer → Polymer + H₂O

• Hydrolysis: Polymer + H₂O → Monomer + Monomer

Macromolecule Summary

Cells contain four major types of macromolecules:

Type	Monomer	Function	Example
Carbohydrates	Monosaccharide	Energy, structure	Starch, cellulose
Lipids	Glycerol + Fatty acids	Energy, membrane	Fats, phospholipids
Proteins	Amino acids	Enzymes, structure	Hemoglobin
Nucleic acids	Nucleotide	Genetic code	DNA, RNA

Protein Structure Levels

• Primary: Linear chain of amino acids

• Secondary: α-helix or β-sheet

• Tertiary: 3D folded shape

• Quaternary: Multiple subunits

Diagram: Phospholipid Bilayer

O = hydrophilic head ||||| = hydrophobic tails O ||||| ||||| O

Chapter 4: A Tour of the Cell

Cell Types Overview

Cells are classified as prokaryotic or eukaryotic based on their structure and complexity.

Feature	Prokaryote	Eukaryote
Nucleus	No	Yes
Organelles	No	Yes
Size	1–10 μm	10–100 μm
Example	Bacteria	Animal/Plant cells

Diagram: Prokaryotic Cell (Simplified)

[Cell wall] [Plasma membrane] [Cytoplasm] [DNA in nucleoid] [Ribosomes] [Flagella (sometimes)]

Diagram: Eukaryotic Animal Cell

[Plasma membrane] [Golgi apparatus] [Rough ER] [Smooth ER] [Nucleus (with nucleolus)] [Mitochondrion] [Peroxisome] [Cytoskeleton]

Diagram: Eukaryotic Plant Cell

[Cell wall] [Chloroplast] [Large central vacuole] [Nucleus] [Mitochondrion] [Golgi apparatus] [ER] [Plasma membrane]

Cytoskeleton Overview

Component	Structure	Function
Microtubules	Hollow tubes	Support, movement, spindle
Microfilaments	Actin chains	Shape, contraction
Intermediate filaments	Fiber cables	Strength, anchors

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts in eukaryotic cells.

[Ancestral eukaryote] + [Engulfed aerobic bacterium] → Mitochondrion [Ancestral eukaryote] + [Engulfed photosynthetic bacterium] → Chloroplast

Plant vs Animal Cells Quick View

Structure	Plant	Animal
Cell wall	✔️	❌
Chloroplast	✔️	❌
Central vacuole	✔️	❌
Lysosomes	❌	✔️
Shape	Boxy	Round

Self-Quiz & Review

1. List the seven properties of life.

2. Explain why water is called the solvent of life.

3. Describe the four major macromolecules and their monomers.

4. Draw and label a prokaryotic and eukaryotic cell.

5. Trace a protein’s path: nucleus → ER → Golgi → plasma membrane.

6. Give two evidences for the endosymbiotic theory.

7. Explain why small cell size improves efficiency.

Study Tip: Draw each diagram from memory until you can label every structure and describe its function aloud. Engaging multiple senses (seeing, saying, writing) helps concepts stick.