Chapter 1 – Introduction to Biology

Characteristics of Living Things

All living organisms share a set of fundamental characteristics that distinguish them from non-living matter.

• Made of cells: All living things are composed of one or more cells, which are the basic units of life. Example: Humans are multicellular; bacteria are unicellular.

• Use energy: Organisms require energy to carry out life processes. Example: Plants use photosynthesis; humans eat food.

• Respond to environment: Living things detect and respond to stimuli. Example: Plants grow toward light.

• Grow and develop: Organisms increase in size and complexity over time. Example: A puppy becomes a dog.

• Reproduce: Organisms produce offspring, either sexually or asexually.

• Maintain homeostasis: Internal conditions are regulated to remain stable. Example: Sweating to cool the body.

• Evolve as a population: Populations change over generations through adaptation. Example: Antibiotic resistance in bacteria.

Homeostasis

• Definition: The maintenance of a stable internal environment despite external changes.

• Example: Humans maintain body temperature at approximately 98.6°F (37°C).

Three Domains of Life

All life is classified into three domains based on cellular structure and genetics.

• Bacteria: Prokaryotic, unicellular, no nucleus, cell walls. Example: E. coli.

• Archaea: Prokaryotic, unicellular, often found in extreme environments. Example: Halophiles.

• Eukarya: Eukaryotic, nucleus and organelles. Examples: Humans, plants, fungi.

Levels of Organization (small → large)

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

1. Atom – e.g., Hydrogen atom

2. Molecule – e.g., Water (H2O)

3. Organelle – e.g., Mitochondria

4. Cell – e.g., Muscle cell

5. Tissue – e.g., Nervous tissue

6. Organ – e.g., Stomach

7. Organ system – e.g., Digestive system

8. Organism – e.g., Human

Scientific Method

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

1. Observation

2. Question

3. Hypothesis

4. Experiment

5. Collect data

6. Analyze results

7. Conclusion

• Independent variable: Manipulated factor (e.g., fertilizer type).

• Dependent variable: Measured outcome (e.g., plant height).

• Inductive reasoning: Specific observations to general patterns (hypothesis formation).

• Deductive reasoning: General theory to specific predictions.

Terminology

• Placebo: Fake treatment.

• Double blind: Neither subject nor experimenter knows who receives treatment.

• Informed consent: Participants agree with full understanding.

• Control group: Baseline group, no treatment.

• Experimental group: Receives treatment.

Chapter 2 – Chemistry of Life

Atoms

Atoms are the smallest units of matter, composed of subatomic particles.

• Protons (+)

• Neutrons (0)

• Electrons (–)

Key Terms

• Element: Pure substance (e.g., Carbon).

• Isotope: Same element, different number of neutrons (e.g., C-12 vs. C-14).

• Compound: Two or more elements chemically bonded (e.g., NaCl).

• Molecule: Smallest unit of a compound (e.g., H2O).

Chemical Bonds

• Ionic bond: Transfer of electrons (e.g., NaCl).

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

  • Polar: Unequal sharing (e.g., H2O).

  • Nonpolar: Equal sharing (e.g., O2).

• Hydrogen bond: Weak attraction between molecules (e.g., water molecules stick together).

pH Scale

The pH scale measures the acidity or basicity of a solution.

• 0–6 = Acidic (high H+) – e.g., Stomach acid

• 7 = Neutral – e.g., Pure water

• 8–14 = Basic/alkaline (high OH–) – e.g., Bleach

• Body protection: Buffers (e.g., bicarbonate buffer in blood) help maintain pH homeostasis.

Macromolecules

Macromolecules are large, complex molecules essential for life.

• Carbohydrates

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

  • Disaccharides: Two sugars (e.g., sucrose)

  • Polysaccharides: Many sugars (e.g., starch, glycogen, cellulose)

  • Formed by dehydration synthesis

• Lipids

  • Triglycerides: Fats for energy storage

  • Phospholipids: Make up cell membranes

  • Steroids: Hormones (e.g., testosterone, estrogen, cholesterol)

• Proteins

  • Made of amino acids

  • Peptide bonds: Link amino acids

  • Denaturation: Protein loses shape (due to heat, pH)

• Nucleic Acids

  • Made of nucleotides (sugar, phosphate, base)

  • DNA: Genetic code

  • RNA: Protein synthesis

  • ATP: Cellular energy

Chapter 3 – Cells

Prokaryotes vs. Eukaryotes

• Prokaryotes: No nucleus or organelles (e.g., bacteria)

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

Cell Membrane

• Composed of a phospholipid bilayer and proteins

Passive Transport (no energy required)

• Facilitated diffusion: Molecules move via protein channels (e.g., glucose)

• Passive diffusion: Molecules move directly (e.g., O2, CO2)

• Osmosis: Water movement

Osmosis Examples

• Isotonic: Equal water, no change (e.g., IV fluids)

• Hypotonic: Water in, cell swells (e.g., red blood cell in pure water)

• Hypertonic: Water out, cell shrinks (e.g., salt water)

Active Transport (requires energy)

• Exocytosis: Vesicle releases contents outside the cell

• Endocytosis: Cell takes material inside

• Phagocytosis: "Cell eating" solids (e.g., WBC engulfing bacteria)

• Pinocytosis: "Cell drinking" fluids

Organelles & Functions

• Nucleus: Stores DNA

• Mitochondria: Makes ATP (energy)

• Ribosomes: Make proteins

• ER (rough): Makes proteins

• ER (smooth): Makes lipids

• Golgi apparatus: Packages proteins

• Lysosome: Breaks down toxins

• Vacuole: Storage

• Cytoskeleton: Structure and transport

• Centrioles: Cell division

• Cilia: Short movement hairs (e.g., respiratory tract)

• Flagella: Long whip tail (e.g., sperm cell)

Cellular Respiration

Cellular respiration is the process by which cells extract energy from glucose.

1. Glycolysis (cytoplasm)

   • Breaks glucose into 2 pyruvate

   • Produces 2 ATP and NADH

2. Citric Acid Cycle (mitochondria)

   • Pyruvate → CO2

   • Produces 2 ATP, NADH, FADH2

3. Electron Transport Chain (mitochondrial inner membrane)

   • Uses NADH/FADH2 to make ATP

   • Produces ~34 ATP and water

Fermentation

• Occurs when no oxygen is available

• Produces lactic acid (muscles) or ethanol (yeast)

• Only 2 ATP produced