AP Biology Review Notes

AP Biology Review Notes

UNIT I: CHEMISTRY OF LIFE

A. Elements
  • All life forms are made up of matter, which is composed of elements.
  • Elements: Substances that cannot be broken down into smaller substances by chemical means.
B. Essential Elements of Life
  • 96% of the mass of all living things is made up of four elements:
    • Oxygen (O)
    • Carbon (C)
    • Hydrogen (H)
    • Nitrogen (N)
  • Other essential elements (4% of biomass):
    • Calcium (Ca)
    • Phosphorus (P)
    • Potassium (K)
    • Sulfur (S)
    • Sodium (Na)
    • Chlorine (Cl)
    • Magnesium (Mg)
  • Trace elements:
    • Iron (Fe)
    • Iodine (I)
    • Copper (Cu)
C. Subatomic Particles
  • Atom: Smallest unit of an element; building blocks of the physical world.
  • Subatomic Particles:
    • Protons:
    • Positively charged, found in nucleus, number of protons = atomic number.
    • Neutrons:
    • No charge, also found in the nucleus.
    • Isotopes: Same element with different amounts of neutrons (vary in mass).
    • Electrons:
    • Negatively charged, orbit around the nucleus, exist in varying energy levels.
    • Valence Electrons: Electrons in the outermost shell, crucial for chemical behavior.
D. Compounds
  • Compounds: Result from the combination of two or more elements in a fixed ratio, leading to different properties from individual elements.
  • Chemical Bonds:
    • Ionic Bonds: Atoms transfer electrons; results in oppositely charged ions (cations and anions).
    • Covalent Bonds: Atoms share electrons; can be polar or nonpolar depending on electronegativity.
    • Hydrogen Bonds: Weak attractions between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.
    • Van der Waals Interactions: Weak attractions due to asymmetrical electron distributions in molecules.
E. Water: The Versatile Molecule
  • Water is polar due to unequal sharing of electrons between hydrogen and oxygen.
  • Properties of Water:
    • Cohesion: Water molecules stick to each other.
    • Adhesion: Water molecules stick to other substances.
    • Surface Tension: Due to cohesion.
    • High Heat Capacity: Water can absorb a lot of heat before changing temperature.
    • Expansion Upon Freezing: Ice is less dense than liquid water, allowing it to float.
    • Versatility as a Solvent: Water can dissolve many substances due to its polarity, making it an excellent solvent.
F. Acids and Bases
  • Acidic Solution: High in H+
  • Alkaline Solution: High in OH-
  • Measured on the pH scale (1-14). Acids are 1-7, bases are 7-14.
  • Buffers: Solutions that stabilize pH by absorbing excess H+ or OH-.
G. Organic Molecules
  • Organic Compounds contain Carbon; Inorganic Compounds do not.
  • Carbon: Versatile atom capable of forming four covalent bonds.
  • Functional Groups: Specific groups of atoms that determine the characteristics and chemistry of organic compounds.
Functional Groups and Their Characteristics:
  • Hydroxyl: -OH; polar, forms hydrogen bonds, and is involved in dehydration reactions.
  • Carbonyl: >C=O; involved in sugar chemistry (ketoses and aldoses).
  • Carboxyl: -COOH; acts as an acid.
  • Amino: -NH2; acts as a base.
  • Sulfhydryl: -SH; stabilizes protein structure.
  • Phosphate: -OPO32-; important in energy transfer and signaling.
  • Methyl: -CH3; affects gene expression and shape/function of hormones.
H. Macromolecules
1. Carbohydrates
  • Monosaccharides: Simple sugars (e.g., glucose and fructose).
  • Disaccharides: Formed from two monosaccharides via dehydration synthesis (glycosidic linkage).
  • Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
2. Proteins
  • Amino Acids: Building blocks of proteins (20 different types).
  • Structure Levels:
    • Primary: Sequence of amino acids.
    • Secondary: Alpha helices or beta sheets formed via hydrogen bonding.
    • Tertiary: Overall 3D shape; stabilized by various interactions (hydrogen bonds, ionic bonds, disulfide bridges).
    • Quaternary: Interaction of multiple polypeptide chains.
  • Enzymatic Functions: Speed up reactions, highly specific.
3. Lipids
  • Diverse group; non-polar; includes fats, phospholipids, and steroids.
  • Triglycerides: Glycerol + 3 fatty acids (storage form).
  • Phospholipids: Major component of cell membranes; amphipathic.
  • Steroids: Structure characterized by four fused rings, e.g., cholesterol.
4. Nucleic Acids
  • DNA and RNA: Carriers of genetic information.
  • Components: Nucleotides (sugar, phosphate group, nitrogenous base).
  • DNA is double-stranded, RNA is single-stranded with Uracil instead of Thymine.
I. The Origin of Life
  • Oparin and Haldane's Theory: Primitive atmosphere contained methane, ammonia, hydrogen, water; no free oxygen.
  • Miller-Urey Experiment: Simulated primitive conditions; produced organic compounds.
  • RNA World Hypothesis: Original life-forms were likely based on RNA.
J. Cells
  • Cell Theory: All living things are composed of cells; cells are the basic unit of life.
  • Prokaryotic Cells: Lack nucleus, simpler structure (bacteria).
  • Eukaryotic Cells: Have nucleus and organelles (plant and animal cells).
  • Organelles: Specialized structures within cells each performing specific functions (e.g., nucleus, mitochondria, ER, golgi apparatus, etc.).

UNIT II: CELLS

A. Cell Structure and Function
  • Plasma Membrane: Semi-permeable, consists of a phospholipid bilayer; regulates movement in/out of the cell.
  • Nucleus: Contains genetic material; regulates cell activities and reproduction.
  • Ribosomes: Sites of protein synthesis.
  • Endoplasmic Reticulum (ER): Rough ER synthesizes proteins, Smooth ER synthesizes lipids.
  • Golgi Apparatus: Processes and packages proteins for secretion.
  • Mitochondria: Powerhouse of the cell; ATP production.
  • Lysosomes: Digestive enzymes, breakdown waste.
B. Transport Across the Plasma Membrane
  • Diffusion: Movement of substances down their concentration gradient.
  • Osmosis: Movement of water across a semi-permeable membrane.
  • Active Transport: Movement against concentration gradient requiring energy.
  • Endocytosis and Exocytosis: Processes to transport large molecules in and out of cells, respectively.

UNIT III: CELLULAR ENERGETICS

A. Bioenergetics
  • First Law of Thermodynamics: Energy cannot be created or destroyed.
  • Second Law of Thermodynamics: Energy transfer leads to increased entropy.
B. Cellular Respiration
  • Glycolysis: Breakdown of glucose to pyruvate; occurs in the cytoplasm.
  • Citric Acid Cycle (Krebs Cycle): Completes glucose oxidation, producing ATP, NADH, FADH2.
  • Oxidative Phosphorylation: Produces the majority of ATP through the electron transport chain.
C. Photosynthesis
  • Light Reactions: Convert solar energy into chemical energy (ATP, NADPH).
  • Calvin Cycle: Uses ATP and NADPH to convert CO2 into glucose.
D. Feedback Mechanisms
  • Negative Feedback: Reduces the output of a system to stabilize the system.
  • Positive Feedback: Enhances the output to produce a result.

UNIT IV: MOLECULAR BIOLOGY

A. DNA and RNA
  • Structure of DNA: Double helix formed by nucleotides; A-T, C-G base pairing.
  • DNA Replication: Semi-conservative process; involves enzymes like helicase and DNA polymerase.
B. Gene Regulation
  • Regulatory sequences control expression; involves transcription factors and enhancers.

UNIT V: CELL REPRODUCTION

A. Mitosis and Meiosis
  • Mitosis: Produces two identical daughter cells; functions include growth and repair.
  • Meiosis: Produces gametes; introduces genetic diversity via crossing over.

UNIT VI: HEREDITY

A. Mendelian Genetics
  • Laws of Inheritance: Dominance, Segregation, and Independent Assortment.
  • Phenotype vs. Genotype: Phenotype refers to observable traits; genotype is genetic makeup.

UNIT VII: EVOLUTIONARY BIOLOGY

A. Natural Selection
  • Mechanism of evolution where advantageous traits become more common.
B. Speciation
  • Formation of new and distinct species through processes such as allopatric and sympatric speciation.
C. Genetic Variability and Drift
  • Importance of genetic variation in populations; mechanisms include mutations and gene flow.

UNIT VIII: ANIMAL STRUCTURE AND FUNCTION

A. Homeostasis
  • Mechanisms maintain stable internal environments through feedback regulation.
B. Organ Systems
  • Each organ system plays roles in maintaining homeostasis and survival.

UNIT IX: BEHAVIOR AND ECOLOGY

A. Behavior
  • Instinct vs. Learning: Different forms of behavior in animals.
B. Communication
  • Mechanisms used by animals to interact and signal information.
C. Ecosystems
  • Interactions between living organisms and their environment.
D. Population Dynamics
  • Factors affecting population size, density, growth, and carrying capacity.
E. Human Impact
  • Understanding ecological issues like pollution, deforestation, and climate change.