Biology Study Guide: Foundations, Chemistry, Cells, Genetics, and Molecular Biology

Chapter 1: Introduction to Biology and the Scientific Method

The Scientific Method

The scientific method is a systematic approach used to investigate natural phenomena. It involves making observations, forming hypotheses, making predictions, conducting experiments, and analyzing results.

• Observation: Gathering information about phenomena or events.

• Hypothesis: A testable explanation for an observation. It is specific and can be supported or refuted by experiments.

• Prediction: A logical statement about what will happen if the hypothesis is correct.

• Experiment: A controlled procedure to test the hypothesis.

• Analysis: Interpreting data to determine if it supports or refutes the hypothesis.

• Hypothesis vs. Theory: A hypothesis is a specific, testable statement; a theory is a broad explanation supported by extensive evidence.

• Dependent Variable: The variable being measured or tested.

• Independent Variable: The variable that is changed or controlled.

• Controls: Conditions kept constant to ensure a fair test.

• Treatments: The experimental conditions applied to test subjects.

Example: Testing the effect of sunlight on plant growth: sunlight exposure is the independent variable, plant growth is the dependent variable, and plants not exposed to sunlight serve as controls.

Unifying Qualities of Life

• Taxonomic Ranks: Hierarchical classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Levels of Organization: Molecule → Organelle → Cell → Tissue → Organ → Organism → Population → Community → Ecosystem → Biosphere.

• Emergent Properties: New properties that arise at each level of organization due to interactions among components.

• Unifying Features: All living things are composed of cells, use DNA, obtain and use energy, grow, reproduce, respond to stimuli, and evolve.

Chapter 2: The Chemical Context of Life

Atomic Structure and Properties

• Atoms: Composed of protons (positive), neutrons (neutral), and electrons (negative).

• Atomic Number: Number of protons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Atomic Mass: Sum of protons and neutrons.

• Valence Shells: Outermost electron shell; determines chemical reactivity.

Chemical Bonding

• Ionic Bonds: Transfer of electrons between atoms (e.g., NaCl).

• Polar Covalent Bonds: Unequal sharing of electrons (e.g., H2O).

• Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., O2).

• Metallic Bonds: Electrons shared among many atoms (common in metals).

pH and Water

• pH Scale: Measures hydrogen ion concentration; logarithmic scale.

• Acidic: pH < 7; higher H+ concentration.

• Basic: pH > 7; lower H+ concentration.

• Water's Properties: Cohesion, adhesion, high specific heat, solvent abilities, ice floats.

• Hydrogen Bonding: Weak bonds between polar molecules, crucial for water's properties.

Equation:

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

Chapter 3: Carbon and the Molecular Diversity of Life

Functional Groups

• Hydroxyl (-OH): Polar

• Carbonyl (C=O): Polar

• Carboxyl (-COOH): Acidic, negatively charged

• Amine (-NH2): Basic, positively charged

• Phosphate (-PO4): Acidic, negatively charged

• Sulfhydryl (-SH): Polar

• Methyl (-CH3): Nonpolar

Macromolecules

• Carbohydrates: Monomers are monosaccharides (e.g., glucose); polymers are polysaccharides (e.g., starch, cellulose).

• Proteins: Monomers are amino acids; polymers are polypeptides.

• Lipids: Glycerol and fatty acids form fats; phospholipids and cholesterol are key components.

• Nucleic Acids: DNA and RNA; monomers are nucleotides.

Example: Starch is a polysaccharide made of glucose monomers.

Chapter 4: A Tour of the Cell

Eukaryotic Organelles and Their Functions

• Nucleus: Contains DNA; site of transcription.

• Endoplasmic Reticulum (ER):

  • Rough ER: Studded with ribosomes; protein synthesis.

  • Smooth ER: Lipid synthesis, detoxification.

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

• Vesicles and Vacuoles: Storage and transport.

• Cell Membrane: Phospholipid bilayer; controls entry/exit of substances.

• Cell Wall: Provides structure (plants, fungi, some protists, bacteria).

• Chloroplasts: Photosynthesis (plants, some protists).

• Mitochondria: Cellular respiration (most eukaryotes).

Example: Animal cells have mitochondria but not chloroplasts; plant cells have both.

Chapter 5: Membrane Structure and Function

Membrane Properties

• Membrane Coherence: Maintained by hydrophobic interactions among phospholipids.

• Fluidity: Affected by temperature, fatty acid chain length, saturation, and cholesterol content.

• Proteins in Membranes: Serve as channels, carriers, receptors, and enzymes.

Transport Mechanisms

• Simple Diffusion: Movement of small, nonpolar molecules down their concentration gradient.

• Facilitated Diffusion: Movement via membrane proteins; no energy required.

• Osmosis: Diffusion of water across a selectively permeable membrane.

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

Chapter 6: Metabolism and Enzymes

Thermodynamics and Metabolism

• First Law: Energy cannot be created or destroyed, only transformed.

• Second Law: Every energy transfer increases entropy (disorder).

• Metabolism: All chemical reactions in a cell.

• Anabolic Pathways: Build complex molecules; require energy.

• Catabolic Pathways: Break down molecules; release energy.

• Exergonic: Release energy ($\Delta G < 0$).

• Endergonic: Require energy ($\Delta G > 0$).

• Hydration: Addition of water.

• Hydrolysis: Breaking bonds using water.

• ATP: Main energy currency of the cell.

Equation:

$\Delta G = \Delta H - T\Delta S$

Enzymes and Regulation

• Enzymes: Biological catalysts; speed up reactions by lowering activation energy.

• Cofactors: Non-protein helpers (metal ions, vitamins).

• Competitive Inhibitors: Bind active site, block substrate.

• Noncompetitive Inhibitors: Bind elsewhere, change enzyme shape.

• Activators: Increase enzyme activity.

Chapter 7: Cellular Respiration and Fermentation

Overview and Equations

• Aerobic Respiration: $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \text{ATP}$

• Anaerobic Respiration: Similar, but final electron acceptor is not oxygen.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

Stages and Locations

• Glycolysis: Cytoplasm; glucose to pyruvate; 2 ATP produced.

• Fermentation: Cytoplasm; lactic acid or alcohol; regenerates NAD+.

• Pyruvate Oxidation: Mitochondrial matrix; pyruvate to acetyl-CoA.

• Krebs Cycle: Mitochondrial matrix; completes glucose breakdown; 2 ATP per glucose.

• Electron Transport Chain: Inner mitochondrial membrane; produces most ATP via oxidative phosphorylation.

ATP Yield: Up to 38 ATP per glucose (aerobic); much less in fermentation.

Chapter 8: Photosynthesis

Overview and Equations

• Photosynthesis: $6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2$

Evolutionary Origins

• Chloroplasts and Mitochondria: Originated via endosymbiosis.

Chloroplast Structure and Processes

• Light Reactions: Occur in thylakoid membranes; inputs: light, water, NADP+, ADP + Pi; outputs: NADPH, ATP, O2.

• Calvin Cycle: Occurs in stroma; inputs: CO2, NADPH, ATP; outputs: glucose, water, NADP+, ADP + Pi.

• Photosystems I and II: Capture light energy; drive electron transport chains.

• Chemiosmotic Gradient: Drives ATP synthesis.

Comparison to Cellular Respiration: Both involve electron transport chains and chemiosmosis, but photosynthesis stores energy, while respiration releases it.

Chapters 9 & 10: The Cell Cycle, Mitosis, and Meiosis

Key Concepts

• Haploid (n): One set of chromosomes.

• Diploid (2n): Two sets of chromosomes.

• Mitosis: Produces genetically identical cells (clones).

• Meiosis: Produces genetically unique gametes or spores.

Phases

• Mitosis: Prophase, Metaphase, Anaphase, Telophase.

• Meiosis I: Homologous chromosomes separate.

• Meiosis II: Sister chromatids separate.

Mechanisms

• Spindles, Microtubules, Centrosomes: Organize chromosome movement.

• Centrosomes: Present in most protists, some fungi, animals, mosses, ferns; absent in most fungi, conifers, flowering plants.

• Cytokinesis: Animal cells: cleavage furrow; plant cells: cell plate.

• Binary Fission: Prokaryotic cell division.

Chapter 11: Mendelian Genetics

Key Concepts

• Punnett Squares: Predict offspring genotypes and phenotypes.

• One-gene and Two-gene Systems: Monohybrid and dihybrid crosses.

• Dominant vs. Recessive: Dominant alleles mask recessive ones; recessive alleles can skip generations.

• Pedigrees: Family trees showing inheritance patterns.

Complex Inheritance

• Codominance: Both alleles expressed (e.g., AB blood type).

• Incomplete Dominance: Intermediate phenotype (e.g., pink flowers from red and white parents).

• Polygenic Inheritance: Multiple genes affect a trait.

• Pleiotropy: One gene affects multiple traits.

Chapter 12: Chromosomal Basis of Inheritance

Sex Chromosomes and Inheritance

• Mammalian/Fruit Fly Sex Chromosomes: X and Y; autosomes are non-sex chromosomes.

• X-linked Traits: Genes on X chromosome; can be dominant or recessive.

• Y-linked Traits: Genes on Y chromosome; only in males.

• Barr Bodies: Inactivated X chromosomes in females.

Gene Linkage and Chromosomal Mapping

• Linkage: Genes on the same chromosome tend to be inherited together.

• Recombination: Crossing over during meiosis increases genetic diversity.

• Chromosomal Maps: Show gene positions based on recombination frequencies.

Nondisjunction and Non-nuclear Inheritance

• Nondisjunction: Failure of chromosomes to separate; leads to aneuploidy.

• Non-nuclear Traits: Inherited via mitochondria, chloroplasts, or prokaryotes.

Chapter 13: The Molecular Basis of Inheritance

Viruses and DNA Replication

• Viruses: Infectious particles; require host cells to replicate.

• DNA Replication: Semi-conservative; each new DNA has one old and one new strand.

• Base Pairing: A-T, G-C; Chargaff's rules: %A = %T, %G = %C.

• Antiparallel Strands: 5' to 3' and 3' to 5' orientation.

• Replication Forks and Bubbles: Sites where DNA is unwound for replication.

• Key Proteins: Helicase (unwinds), Primase (RNA primer), DNA polymerases (synthesize DNA), Ligase (joins fragments), repair enzymes.

• DNA Polymerases: Three main types in prokaryotes: I, II, III.

• Telomeres: Repetitive DNA at chromosome ends; protect from degradation.

Equation:

$\text{DNA Replication:} \quad \text{(Parent DNA)} \rightarrow \text{(2 Daughter DNAs)}$

Chapter 14: Gene Expression: From Gene to Protein

Transcription and Translation

• Transcription: DNA to mRNA; occurs in nucleus; RNA polymerase is key enzyme.

• Translation: mRNA to protein; occurs in cytoplasm/ribosome.

• Genetic Code: Redundant (multiple codons per amino acid), but not ambiguous.

Practice Problems

• Be able to transcribe DNA to mRNA, translate mRNA to tRNA, and use codon tables to determine amino acids.

Mutations

• Point Mutations:

  • Silent: No amino acid change.

  • Missense: Changes one amino acid.

  • Nonsense: Creates a stop codon.

• Chromosomal Rearrangements: Deletions, insertions, inversions, translocations, polyploidy.

Example: Sickle cell anemia is caused by a missense mutation in the hemoglobin gene.