IB Biology SL/HL Comprehensive Review and Study Guide

Water and the Foundations of Life (Sections 2.8-2.13)

• Polarity and Hydrogen Bonding: Water molecules are polar due to the unequal sharing of electrons between oxygen and hydrogen. This polarity allows for the formation of hydrogen bonds between water molecules.

• Properties of Water:     * Solvent Properties: Water's polarity makes it an excellent solvent for polar and ionic substances.     * Thermal Properties: Includes high specific heat capacity and high latent heat of vaporization, providing temperature stability for organisms.     * Cohesion and Adhesion: Cohesion is the attraction between water molecules (surface tension); adhesion is the attraction between water molecules and other surfaces (capillary action).

Molecules to Metabolism (Sections 3.1-3.3)

• Monomers and Polymers: Biological macromolecules are built from repeating subunits (monomers) into larger chains (polymers).

• Metabolic Reactions:     * Hydrolysis (Catabolic): The chemical breakdown of a compound due to reaction with water; it breaks polymers into monomers.     * Condensation/Dehydration (Anabolic): The joining of monomers to form a polymer with the removal of a water molecule.

• Macromolecule Diagrams: Identification and diagramming of reactions for carbohydrates, lipids, and proteins.

• Peptide Bonds: Identifying the specific bond formed between amino acids in a dipeptide or polypeptide chain.

Carbohydrates, Lipids, Proteins, and Nucleic Acids (Sections 3.4-3.15)

• Chemical Composition: Identification of the specific atoms composing these macromolecules, including Nucleic Acids.

• Carbohydrates:     * Categories: Monosaccharides (simple sugars), disaccharides (two sugars), and polysaccharides (complex chains).     * Functions: Specific roles of glucose, starch, glycogen, and cellulose.

• Lipids:     * Fatty Acids: Classification into saturated (no double bonds) vs. unsaturated (double bonds present), and unsaturated into Cis vs. Trans isomers.     * Types: Triglycerides (energy storage), phospholipids (membrane structure), and steroids (hormone signaling).

• Proteins: Composed of amino acid monomers joined by peptide bonds. They perform diverse biological functions.

• Nucleic Acids: Includes Nucleotides, DNA, RNA, and ATP.

Introduction to Cells and Ultrastructure (Sections 4.2-4.15)

• Cell Theory: The fundamental principle that all living things are composed of cells, the cell is the basic unit of life, and cells come from pre-existing cells.

• Characteristics of Life: Shared traits of all life forms, including unicellular organisms that perform every life process individually.

• Cell Size Limitations: The significance of the surface area to volume ratio ($SA:V$) in limiting cell size; as a cell grows, volume increases faster than surface area, making material exchange inefficient.

• Cell Types:     * Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes contain a nucleus and specialized organelles.     * Organelles: Functions of specific structures in animal and plant cells.     * Plant vs. Animal Cells: Differences such as cell walls and chloroplasts in plants vs. centrioles in animals.

• Endosymbiotic Theory: The theory explaining the origin of eukaryotic organelles (chloroplasts and mitochondria) through the engulfing of prokaryotes.

Membrane Structure and Transport (Sections 5.1-5.9)

• Membrane Components: Includes phospholipids (hydrophobic tails/non-polar and hydrophilic heads/polar), peripheral and integral proteins, glycoproteins, enzymes, and transport proteins.

• Transport Mechanisms:     * Passive Transport: Diffusion and osmosis (movement of water).     * Active Transport: Movement against the concentration gradient requiring energy.     * Vesicle Transport: Endocytosis (moving materials into the cell) and exocytosis (moving materials out of the cell).

• Tonicity (Sections 5.4-5.5):     * Hypotonic: Lower solute concentration outside; water moves in (cell becomes turgid or lysed).     * Hypertonic: Higher solute concentration outside; water moves out (cell becomes plasmolyzed).     * Isotonic: Equal solute concentration; no net water movement (cell is flaccid).     * Case Study: Identifying states in onion cells (plasma membrane, cell wall, and cytoplasm labels).

Enzymes (Sections 5.13-5.15)

• Terminology:     * Catalyst: A substance that speeds up a chemical reaction without being consumed.     * Active Site: The specific region on the enzyme where the substrate binds.     * Enzyme vs. Substrate: The enzyme is the biological catalyst; the substrate is the reactant it acts upon.

• Specificity: The "Lock and Key" model describes how an enzyme's active site is specific to a particular substrate.

• Factors Affecting Enzyme Action:     * Temperature.     * pH levels.     * Substrate concentration.

• Enzyme Inhibition:     * Competitive Inhibition: Inhibitor binds to the active site.     * Non-competitive Inhibition: Inhibitor binds to an allosteric site, changing the active site shape.     * End-product Inhibition: The final product of a pathway inhibits an earlier enzyme.

Cell Division and Meiosis (Sections 8.4-8.18)

• The Cell Cycle: Comprised of Interphase, Mitosis, and Cytokinesis; regulated by proteins called cyclins.

• Mitosis: Identifying stages (Prophase, Metaphase, Anaphase, Telophase) in onion root tips.

• Meiosis: The process of creating haploid gametes from diploid cells.     * Genetic Variation: Driven by crossing over (Prophase I) and random alignment/independent assortment (Metaphase I).     * Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to genetic disorders.

Molecular Genetics (Sections 10.4-10.15)

• Structure of DNA and RNA:     * Nucleotide structure: Sugar, phosphate, and nitrogenous base.     * Bases: Adenine (A), Thymine (T - DNA only), Uracil (U - RNA only), Cytosine (C), Guanine (G).     * DNA is double-stranded and antiparallel ($3'$ and $5'$ ends); RNA is single-stranded.     * Complementary base pairing rules (A with T/U, C with G).

• DNA Replication:     * Model: Semi-conservative (proven by the Meselson & Stahl experiment).     * Enzymes: Helicase (unwinds), Primase (adds primers), DNA Polymerase III (adds nucleotides), DNA Polymerase I (removes primers), Ligase (seals fragments).     * Strands: Leading strand (continuous) vs. Lagging strand (discontinuous/Okazaki fragments).

• Transcription and Translation:     * Transcription: Process of making mRNA from DNA via RNA polymerase.     * Translation: mRNA is read by ribosomes; tRNA brings amino acids based on mRNA codons.

Inheritance (Chapter 9 and Section 11.2)

• Definitions: Genotype, phenotype, dominant, recessive, codominant, locus, homozygous, heterozygous, test cross, carrier, pure breeding.

• Genetic Conditions: Human diseases caused by autosomal recessive alleles (e.g., Sickle Cell Anemia).

• Inheritance Patterns:     * Mendelian Monohybrid and Dihybrid crosses.     * Incomplete dominance, Codominance (e.g., Blood Typing).     * Sex-linked traits, Polygenic inheritance, and Linked genes.

• Tools: Punnett squares and Pedigree charts.

Evolution and Speciation (Sections 13.4, 13.6)

• Core Concepts: Natural Selection, Artificial Selection, Homologous structures (evidence of common ancestry), Analogous structures, and Adaptive radiation.

• Examples of Natural Selection:     * Darwin’s finches (beak variation).     * Industrial melanism (peppered moths).     * Antibiotic resistance in bacteria.

• Phylogenetics: Clades, Cladistics, and interpreting Cladograms.

• Speciation: Sympatric (same area) vs. Allopatric (geographically separated).

Ecology and Environmental Science (Chapters 36, 37, 38)

• Terminology: Autotroph (producer), Heterotroph (consumer), Saprotroph, Decomposer, Species, Population, Community, Ecosystem, Abiotic vs. Biotic factors.

• Trophic Levels: Diagramming food webs including primary, secondary, tertiary, and quaternary consumers.

• Energy and Nutrients: Energy flows one-way through an ecosystem, while nutrients cycle.

• Atmospheric Science:     * Greenhouse Effect: Diagramming how greenhouse gases trap heat.     * Carbon Cycle: Diagramming carbon movement and the link between atmospheric $CO_2$ and global temperatures.

• Populations:     * Growth Curves: Exponential vs. Sigmoid (S-shaped) growth.     * Factors: Density-dependent vs. Density-independent factors.     * Estimation: Random sampling and the Lincoln Index ($Capture-Mark-Release$).     * Statistics: Using Chi-Square to determine if species association is statistically significant.

Biotechnology and Methodology (Chapter 12)

• PCR (Polymerase Chain Reaction): Process used to amplify DNA sequences.

• Gel Electrophoresis: Separating DNA fragments by size for crime scene investigation or paternity tests.

• Genetic Modification: Using plasmids for transgenics (e.g., human insulin production).

• Karyotyping: Visualizing an individual's chromosomal complement.

Key Bio-Chemical Equations

• Cellular Respiration:     $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (ATP)}$

• Photosynthesis:     $6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2$

• Connections: Cellular respiration occurs in the mitochondria (releasing $CO_2$); photosynthesis occurs in the chloroplast (using $CO_2$).