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AP Biology Study Guide

1. Introduction to AP Biology

AP Biology provides a deep understanding of key biological concepts, principles, and processes. Students develop skills in scientific inquiry, investigation, and reasoning, while exploring cellular biology, genetics, evolution, ecology, and more.

Exam Format:

  • Multiple-choice questions: Test comprehension of biological concepts and principles.
  • Free-response questions: Assess the ability to analyze and interpret experimental data, construct logical explanations, and apply biological principles.

2. Biochemistry and the Molecular Biology of Cells

Macromolecules:

  • Carbohydrates: Organic compounds composed of carbon, hydrogen, and oxygen. Serve as energy sources and structural components.
    • Monosaccharides (e.g., glucose)
    • Polysaccharides (e.g., starch, glycogen, cellulose)
  • Proteins: Made of amino acids linked by peptide bonds. Enzymes are a type of protein that catalyze biochemical reactions.
    • Structure: Primary, secondary, tertiary, and quaternary structures.
  • Lipids: Hydrophobic molecules that include fats, oils, and phospholipids. Serve as energy storage and membrane components.
  • Nucleic Acids: DNA and RNA store and transmit genetic information.
    • DNA is double-stranded and stores genetic information.
    • RNA is single-stranded and aids in protein synthesis.

Cell Membrane:

  • The cell membrane is made of a phospholipid bilayer with embedded proteins that control the movement of substances into and out of the cell.
  • Active Transport: Movement of substances against their concentration gradient using energy (e.g., sodium-potassium pump).
  • Passive Transport: Movement of substances down their concentration gradient without energy (e.g., diffusion, osmosis).

3. Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells:

  • Prokaryotic cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria).
  • Eukaryotic cells: Have a nucleus and membrane-bound organelles (e.g., plant and animal cells).

Organelles and Their Functions:

  • Nucleus: Contains DNA and controls cell activities.
  • Mitochondria: The powerhouse of the cell, generating ATP through cellular respiration.
  • Endoplasmic Reticulum (ER): The rough ER synthesizes proteins, and the smooth ER synthesizes lipids.
  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
  • Lysosomes: Contain enzymes that break down waste materials and cellular debris.
  • Chloroplasts (in plants): Conduct photosynthesis, converting solar energy into chemical energy.

4. Genetics and Heredity

Mendelian Genetics:

  • Dominant and Recessive Traits: Dominant alleles mask the expression of recessive alleles.
  • Genotype vs. Phenotype:
    • Genotype is the genetic makeup (e.g., AA, Aa, aa).
    • Phenotype is the physical expression of the genotype.
  • Punnett Squares: A tool used to predict the probability of offspring inheriting specific alleles.

Genetic Disorders:

  • Cystic Fibrosis: Caused by a recessive allele; affects the lungs and digestive system.
  • Sickle Cell Anemia: Caused by a mutation in the hemoglobin gene; results in abnormally shaped red blood cells.

DNA Structure and Replication:

  • Structure: DNA is a double helix made of nucleotides (adenine, thymine, cytosine, and guanine).
  • Replication: The process by which DNA makes an exact copy of itself during cell division. Enzymes like DNA polymerase facilitate this process.

5. Evolution and Natural Selection

Theory of Evolution:

  • Charles Darwin proposed that species evolve through natural selection. Individuals with traits that are better suited to their environment are more likely to survive and reproduce, passing on these advantageous traits.

Mechanisms of Evolution:

  • Mutation: Changes in DNA sequences that can lead to new traits.
  • Gene Flow: The movement of genes between populations through migration.
  • Genetic Drift: Random changes in allele frequencies due to chance.
  • Natural Selection: Favoring of advantageous traits.
  • Sexual Selection: Preference of mates with certain traits.

Evidence for Evolution:

  • Fossils: Show the progression of life forms over time.
  • Homologous Structures: Similar structures in different species, indicating common ancestry.
  • Vestigial Structures: Non-functional remnants of organs that were useful to ancestors.
  • Molecular Evidence: Similarities in DNA, RNA, and protein sequences across species.

6. Ecology and the Environment

Ecological Levels of Organization:

  • Individual Organism: A single organism.
  • Population: A group of individuals of the same species living in an area.
  • Community: Different populations of species living together.
  • Ecosystem: A community and its physical environment.
  • Biome: Large ecosystems defined by climate and dominant vegetation (e.g., desert, rainforest).

Energy Flow in Ecosystems:

  • Trophic Levels: Producers (plants) → Primary consumers (herbivores) → Secondary consumers (carnivores).
  • Food Chains and Food Webs: Models showing the flow of energy through an ecosystem.
  • Energy Pyramids: Illustrate the amount of energy available at each trophic level, with energy decreasing as it moves up the pyramid.

Biogeochemical Cycles:

  • Water Cycle: Describes the movement of water through the environment (evaporation, condensation, precipitation).
  • Carbon Cycle: The movement of carbon between the atmosphere, organisms, and the earth (photosynthesis, respiration, decomposition).
  • Nitrogen Cycle: The process by which nitrogen is converted between different chemical forms, making it accessible to living organisms (nitrogen fixation, nitrification, denitrification).

7. Cellular Respiration and Photosynthesis

Cellular Respiration:

  • Glycolysis: The breakdown of glucose into pyruvate, producing a small amount of ATP.
  • Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondria, producing electron carriers (NADH and FADH2) and small amounts of ATP.
  • Electron Transport Chain (ETC): Uses electron carriers to produce ATP in the mitochondria. Oxygen is the final electron acceptor, forming water.

Photosynthesis:

  • Light-dependent Reactions: Occur in the thylakoid membranes of the chloroplasts, converting light energy into chemical energy (ATP and NADPH).
  • Calvin Cycle: Occurs in the stroma of the chloroplasts, using ATP and NADPH to convert carbon dioxide into glucose.