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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

  • Observation

  • Question

  • Hypothesis

  • Experiment

  • Data analysis

  • 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

Example: A human (organism) is made of organ systems, which are made of organs, tissues, cells, and so on.

3. Basic Chemistry

Atoms and Elements

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

  • Atomic number: Number of protons

  • Isotopes: Same element, different number of 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

  • Carbon forms 4 bonds, allowing for 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 molecules

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

  • Functions: Energy storage, membranes, hormones

Proteins

  • Monomer: Amino acids (20 types)

  • Bond: Peptide bond

  • Levels of structure:

    • Primary (sequence)

    • Secondary (α-helix, β-sheet)

    • Tertiary (3D shape)

    • Quaternary (multiple polypeptides)

  • Denaturation: Loss of structure due to heat, pH, or salt

Nucleic Acids

  • DNA vs. RNA

  • Monomer: Nucleotide (sugar, phosphate, base)

  • 5' → 3' directionality

  • 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 (e.g., bacteria)

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

Organelles (structure & function)

  • Nucleus: Contains DNA

  • Ribosome: Protein synthesis

  • Rough/Smooth ER: Protein/lipid synthesis

  • Golgi: Modifies, sorts, ships proteins

  • Lysosome: Digestion

  • Vacuole: Storage

  • Mitochondria: ATP production

  • Chloroplast: Photosynthesis (plants)

  • Cytoskeleton: Structure, movement

8. Cell Membranes

Structure

  • Fluid-mosaic model: Phospholipid bilayer with embedded proteins

  • Selectively permeable

Transport

  • Passive: Diffusion, osmosis, facilitated diffusion (no energy required)

  • Active: Pumps (require ATP)

  • Bulk: Endocytosis, exocytosis

9. Metabolism & Enzymes

Metabolic Pathways

  • Catabolism: Breaks down molecules, releases energy

  • Anabolism: Builds molecules, requires energy

  • Free energy equation:

  • Exergonic: (spontaneous)

  • Endergonic: (requires energy)

  • ATP couples reactions

Enzymes

  • Lower activation energy

  • Affected by temperature, pH

  • Regulation: Allosteric, competitive inhibition, feedback inhibition

10. Cellular Respiration

Overview

Stages

  1. Glycolysis: In cytosol; glucose → 2 pyruvate, 2 ATP, 2 NADH

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

  3. Citric Acid Cycle (Krebs): Acetyl-CoA → 2 ATP, 6 NADH, 2 FADH2, 4 CO2

  4. Electron Transport Chain (ETC) & Chemiosmosis: NADH/FADH2 donate electrons, create proton gradient, ATP synthase makes ATP, O2 is final electron acceptor (forms water)

Total theoretical yield: 38 ATP per glucose (in prokaryotes; eukaryotes yield slightly less)

11. Photosynthesis

Equation

Light Reactions

  • Occur in thylakoid membrane

  • Split water, release O2

  • Produce ATP & NADPH

Calvin Cycle

  • Occurs in stroma

  • Uses ATP & NADPH to fix CO2

  • Produces G3P (used to make glucose)

  • RuBisCO: Enzyme that fixes CO2, but can also bind O2 (photorespiration)

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

  • Function: Growth and repair

Meiosis

  • Produces 4 non-identical haploid cells (gametes)

  • Meiosis I: Homologous chromosomes separate

  • Meiosis II: Sister chromatids separate

  • Key: Crossing over in Prophase I increases genetic variation

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 type

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 (mosaic females, e.g., calico cats)

14. Chromosomes & Disorders

Nondisjunction

  • Failure of chromosomes to separate during meiosis

  • Results:

    • Trisomy 21 (Down syndrome)

    • XO (Turner syndrome)

    • XXY (Klinefelter syndrome)

Structural Changes

  • Deletion (e.g., Cri du chat)

  • Duplication

  • Inversion

  • Translocation

Exam Preparation Tips

  • Expect pathway input/output questions

  • Be able to compare/contrast concepts

  • Practice 'What happens if...' scenarios

  • Work through genetics crosses

  • Interpret diagrams

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