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General Biology I: Core Concepts and Processes

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1. What Is Science & Biology

Definition and Scope

  • Science: A systematic way of knowing based on observation, experimentation, and testing explanations.

  • Biology: The scientific study of life and living organisms.

  • Hypothesis-based science: Uses testable, falsifiable hypotheses to explain natural phenomena.

Scientific Method

  • 1. Observation

  • 2. Question

  • 3. Hypothesis

  • 4. Experiment

  • 5. Data analysis

  • 6. Conclusion

  • Theory: A broad explanation supported by extensive evidence (not a guess).

2. Levels of Biological Organization

Hierarchy of Life

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

3. Basic Chemistry

Atoms and Elements

  • Protons (+), Neutrons (0), Electrons (−)

  • Atomic number: Number of protons

  • Isotopes: Same element, different neutrons

  • Half-life: Time for half of a radioactive isotope to decay

Bonds

  • Strong: Covalent, Ionic

  • Weak: Hydrogen bonds, Van der Waals forces

  • Polar covalent: Unequal sharing of electrons (water)

  • Nonpolar covalent: Equal sharing of electrons (O2)

4. Water & pH

Properties of Water

  • Cohesion, adhesion

  • High specific heat

  • Ice is less dense than liquid water

  • Excellent solvent

Acids & Bases

  • Acid: Donates H+

  • Base: Accepts H+

  • pH scale: 0–14 (7 is neutral)

  • Buffers: Resist changes in pH

5. Organic Chemistry & Biomolecules

Carbon and Functional Groups

  • 4 bonds → diverse molecules (chains, rings, isomers)

Functional Groups (structure & function)

  • Hydroxyl (–OH)

  • Carbonyl (–CO)

  • Carboxyl (–COOH)

  • Amino (–NH2)

  • Sulfhydryl (–SH)

  • Phosphate (–PO4)

  • Methyl (–CH3)

6. Biomolecules

Carbohydrates

  • Monomer: Monosaccharide

  • Ratio: C : H : O = 1 : 2 : 1

  • Glycosidic linkages: α-linkages (starch, glycogen), β-linkages (cellulose)

  • Functions: Energy, structure, recognition

Lipids

  • Hydrophobic

  • Types: Fats (saturated vs. unsaturated), phospholipids (membranes), steroids (cholesterol)

  • Functions: Energy storage, membranes, hormones

Proteins

  • Monomer: Amino acids (20 types)

  • Bond: Peptide bond

  • Levels:

    • Primary (sequence)

    • Secondary (α-helix, β-sheet)

    • Tertiary (3D shape)

    • Quaternary (multiple polypeptides)

  • Denaturation: Heat, pH, salt

Nucleic Acids

  • DNA vs. RNA

  • Monomer: Nucleotide (sugar, phosphate, base)

  • 5' → 3' direction

  • Complementary base pairing

7. Cell Structure

Cell Theory

  • All living things are made of cells

  • Cells are the basic unit of life

  • Cells come from pre-existing cells

Prokaryotes vs. Eukaryotes

  • Prokaryotes: No nucleus

  • Eukaryotes: Nucleus, organelles

Organelles (structure & function)

  • Nucleus

  • Ribosome

  • Rough/Smooth ER

  • Golgi apparatus

  • Lysosome

  • Vacuole

  • Mitochondria

  • Chloroplast

  • Cytoskeleton

8. Cell Membranes

Structure and Function

  • Fluid-mosaic model: Phospholipid bilayer with proteins

  • Selectively permeable

Transport Mechanisms

  • Passive: Diffusion, osmosis, facilitated diffusion

  • Active: Pumps (require ATP)

  • Bulk: Endocytosis, exocytosis

9. Metabolism & Enzymes

Metabolic Pathways

  • Catabolism: Breaks down molecules

  • Anabolism: Builds up molecules

  • Exergonic: Releases energy ()

  • Endergonic: Requires energy ()

  • ATP couples reactions

Enzymes

  • Lower activation energy

  • Affected by temperature, pH

  • Regulation: Allosteric, feedback inhibition, competitive inhibition

10. Cellular Respiration

Overview

  • Glucose + O2 → CO2 + H2O + ATP

Stages

  1. Glycolysis: Cytosol; input: glucose; output: 2 ATP, 2 NADH, 2 pyruvate

  2. Pyruvate Oxidation: Pyruvate → Acetyl-CoA + CO2 + NADH

  3. Citric Acid Cycle: Output per glucose: 2 ATP, 6 NADH, 2 FADH2, 4 CO2

  4. ETC & Chemiosmosis: Final electron acceptor: oxygen; produces most ATP

  • Total theoretical yield: 38 ATP

11. Photosynthesis

Equation

  • 6 CO2 + 12 H2O + light → C6H12O6 + 6 H2O + 6 O2

Light Reactions

  • Location: Thylakoid membrane

  • Split water → O2 released

  • Make ATP & NADPH

Calvin Cycle

  • Location: Stroma

  • Uses ATP & NADPH to fix CO2

  • Produces G3P (used to make glucose)

C3, C4, CAM Plants

Type

Strategy

C3

Normal

C4

Spatial separation

CAM

Temporal separation

12. Cell Cycle & Division

Mitosis

  • Produces 2 identical diploid cells

  • Stages: Prophase → Metaphase → Anaphase → Telophase

  • Growth & repair

Meiosis

  • Produces 4 non-identical haploid cells

  • Sexual reproduction

  • Meiosis I: Homologous chromosomes separate

  • Meiosis II: Sister chromatids separate

  • Produces haploid gametes

13. Genetics

Mendelian Principles

  • Law of Segregation: Alleles separate during gamete formation

  • Law of Independent Assortment: Genes assort independently if unlinked

Inheritance Patterns

Pattern

Example

Incomplete dominance

Pink flowers

Codominance

AB blood

Polygenic

Height

Epistasis

Labrador coat color

Sex-Linked Traits

  • Males: XY

  • Females: XX

  • Males express recessive X-linked traits more often (e.g., color blindness, hemophilia)

  • X-inactivation: One X becomes Barr body (e.g., calico cats)

14. Chromosomes & Disorders

Nondisjunction

  • Failure of chromosomes to separate

  • Results:

    • Trisomy 21 (Down syndrome)

    • XO (Turner syndrome)

    • XXY (Klinefelter syndrome)

Structural Changes

  • Deletion

  • Duplication

  • Inversion

  • Translocation

Exam Preparation Tips

  • Pathway input/output questions

  • Compare/contrast

  • "What happens if..." scenarios

  • Genetics crosses

  • Diagram interpretation

Additional info: Where content was brief, standard academic context and definitions were added for clarity and completeness.

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