AP Biology Review

AP Biology Study Guide

Key Exam Details

  • The AP Biology exam is a 3-hour, end-of-course test comprised of:   - 60 multiple-choice questions: 1 hour and 30 minutes (50% of score)   - 6 free-response questions: 1 hour and 30 minutes (50% of score)

Course Content Categories

  • Chemistry of Life: 8–11% of test questions

  • Cell Structure and Function: 10–13% of test questions

  • Cellular Energetics: 12–16% of test questions

  • Cell Communication and Cell Cycle: 10–15% of test questions

  • Heredity: 8–11% of test questions

  • Gene Expression and Regulation: 12–16% of test questions

  • Natural Selection: 13–20% of test questions

  • Ecology: 10–15% of test questions

  • Unit 1

Chemistry of Life

Overview

  • Covers approximately 8–11% of exam questions.

Water and the Elements of Life

  • Chemical Composition of Water: Water is comprised of two hydrogen atoms covalently bonded to an oxygen atom. The oxygen atom has a slight negative charge, whereas hydrogen atoms have a slight positive charge, making water a polar compound.

  • Polar Nature and Hydrogen Bonds: The polar nature allows water to form hydrogen bonds, which are weak interactions between a proton in one molecule and an electronegative atom of another molecule.

  • Importance to Life:   - Water acts as a solvent for many biological molecules, facilitating distribution throughout organisms.   - Cohesion (water molecules sticking together) contributes to surface tension, allowing phenomena like water droplets.   - Adhesion (attraction to dissimilar molecules) is significant for capillary action, enabling water movement against gravity in plants.

Organic Molecules

  • Basic Elements: Carbon, hydrogen, nitrogen, and oxygen make up 99% of all living matter.

  • Carbon's Unique Properties: Carbon can form four bonds, allowing diverse configurations like rings and chains, which are foundational to carbohydrates, proteins, lipids, and nucleic acids.

Macromolecules

  1. Polymers: Large biological molecules made of repeating smaller units called monomers.    - DNA: Made of nucleotides.    - Proteins: Made of amino acids.    - Carbohydrates: Made of sugars.

  2. Formation: Biological macromolecules are formed through dehydration synthesis (removing water) and broken down by hydrolysis (adding water).

  3. Energy Considerations: Synthesis requires energy, while hydrolysis releases energy for cellular use.

Proteins

  • Structure: Made of amino acids linked by peptide bonds.   - Amino Acid Structure: Contains a central carbon, amino group (NH₂), carboxyl group (COOH), hydrogen atom, and an R group.

  • Protein Structures:   - Primary Structure: Sequence of amino acids.   - Secondary Structure: Folding into α-helixes and β-sheets due to hydrogen bonding in the backbone.   - Tertiary Structure: 3D shape formed by interactions between R groups.   - Quaternary Structure: Formation of functional proteins through multiple polypeptide chains.

Carbohydrates

  • Formula: General formula is (CH₂O)ₙ.

  • Classification: Monosaccharides (glucose, fructose, galactose), disaccharides (sucrose, lactose, maltose), and polysaccharides (starch, cellulose, glycogen).

  • Bonding: Glycosidic bonds form by dehydration synthesis.

Lipids

  • Characteristics: Nonpolar macromolecules primarily made of hydrocarbon chains.

  • Types: Include fats (triglycerides), phospholipids (membrane components), and steroids.

  • Saturation: Saturated fatty acids have only single bonds, while unsaturated have one or more double bonds, leading to different physical properties (e.g. cis/trans configuration).

Structure of DNA and RNA

  • DNA: Composed of nucleotides (deoxyribose sugar, phosphate group, nitrogenous base). The DNA structure is a double helix formed by complementary base pairing via hydrogen bonds (A-T and C-G in DNA; A-U in RNA).

  • RNA: Typically single-stranded, uses ribose, and uracil instead of thymine.

Links to outside reading provide additional context on water properties, macromolecular structure, and nucleic acid functionality.

Sample Chemistry of Life Questions

  1. Complementary Base Pairs: The strongest complementary base pair in DNA?    - Correct Answer: D. Cytosine and Guanine (3 hydrogen bonds).

  2. Capillary Action: Water travels up a stem via?    - Correct Answer: B. Cohesion-tension.

  3. Carboxylic Acids: Which functional group indicates a carboxylic acid?    - Correct Answer: C. –COOH.

  • Unit 2

Cell Structure and Function

Overview

  • Covers approximately 10–13% of exam questions.

  • Cells are categorized as prokaryotic (no membrane-bound organelles) or eukaryotic (with organelles).

Prokaryotic vs Eukaryotic Cells

  • Prokaryotes: Include bacteria and archaea. Typically single-celled with a circular chromosome.

  • Eukaryotes: Include plants, animals, fungi. Have multiple linear chromosomes within a nucleus and various organelles like mitochondria, chloroplasts, etc.

Cell Components

  1. Nucleus: Contains genetic material as chromatin. Site of RNA processing.

  2. Mitochondria: Sites of ATP synthesis through cellular respiration.

  3. Chloroplasts: Sites of photosynthesis in plant cells.

  4. Endoplasmic Reticulum: Rough ER synthesizes proteins, Smooth ER synthesizes lipids.

  5. Golgi Apparatus: Modifies, sorts, and packages proteins.

  6. Ribosomes: Translate RNA into proteins; exist freely or on Rough ER.

  7. Lysosomes and Peroxisomes: Contain enzymes that degrade waste.

  8. Cytoskeleton: Provides structural support and mediates intracellular transport.

  9. Centrosomes: Organize microtubules and mitotic spindle.

  10. Vesicles: Transport materials within the cell.

Understanding organelle functions is essential for answering free response questions on the AP exam.

Cell Size and Surface Area

  • As cells grow, their surface area must support their metabolic needs.

  • Mathematically: Volume grows faster than surface area, limiting cell size.

  • Specific equations capture relationships for different shapes (sphere, cube, etc.).

Cell Membrane Structure and Function

  • The fluid mosaic model describes cell membranes as a phospholipid bilayer with embedded proteins.

  • Transport Mechanisms:   - Passive Transport: Includes diffusion and facilitated diffusion (e.g., via aquaporins).   - Active Transport: Requires energy (ATP).   - Endocytosis & Exocytosis: Methods for large molecule transport.

Osmosis and Tonicity

  • Osmosis: Movement of water across a semipermeable membrane.

  • Tonicity: Describes relative solute concentrations (isotonic, hypotonic, hypertonic).

Cellular Compartmentalization

  • Organelles keep processes separated to increase cell efficiency.

Evolution of Membrane-Bound Organelles

  • Theory of endosymbiosis suggests that some organelles originated from prokaryotic cells engulfed by eukaryotes.

Links provide additional insights on cell organization and transport mechanisms.

Sample Cell Structure and Function Questions

  1. Protein Production: Cell producing many proteins would likely have:    - Correct Answer: A. Extensive Rough ER.

  2. Hypotonic Solutions: A solution with lower solute concentration:    - Correct Answer: A. Hypotonic.

  3. Plant Cell Properties: Prevents bursting in aqueous solutions:    - Correct Answer: C. Cell wall.

  • Unit 3

Cellular Energetics

Overview

  • Accounts for about 12–16% of questions.

Enzyme Function

  • Activation Energy: The minimum energy required for a reaction.

  • Enzymes: Biological catalysts that lower activation energy.   - Mechanisms: Binding occurs at the active site, forming enzyme-substrate complexes.   - Environmental Effects: Temperature, pH, substrate concentration, and the presence of inhibitors can affect enzyme activity.

Energy in Living Systems

  • Metabolism: Sum of all energy transformations.   - Anabolism vs. Catabolism: Anabolic reactions build up and store energy; catabolic reactions break down and release energy.

  • ATP: Main energy currency in cells, can be generated through various metabolic pathways.

Photosynthesis

  • Equation:   6CO2+6H2O+extLightightarrowC6H12O6+6O26CO_2 + 6H_2O + ext{Light} ightarrow C_6H_{12}O_6 + 6O_2

  • Two Main Phases:   - Photolysis: Light-dependent reactions that produce ATP and NADPH.   - Calvin Cycle: Light-independent reactions that use ATP and NADPH to synthesize glucose.

Cellular Respiration

  • Processes by which cells break down glucose for energy.

  1. Glycolysis: Converts glucose to pyruvate, producing some ATP and NADH.

  2. Pyruvate Oxidation: Converts pyruvate to Acetyl-CoA in mitochondria.

  3. Krebs Cycle: Produces ATP, NADH, and FADH₂.

  4. Oxidative Phosphorylation: Uses electron transport chain to produce ATP, with oxygen as the final electron acceptor. If oxygen is absent, fermentation occurs.

Further links provide insights into cellular energetics and metabolic pathways.

Sample Cellular Energetics Questions

  1. Enzymatic Function: Enzymes lower the:    - Correct Answer: B. Activation energy.

  2. Photosynthesis Product: Light-dependent reactions produce:    - Correct Answer: D. Electrons.

  3. Anaerobic Respiration Product: End product of anaerobic respiration:    - Correct Answer: B. Lactic acid.

  • Unit 4

Cell Communication and Cell Cycle

Overview

  • Covers approximately 10–15% of questions.

Cell Communication Mechanisms

  • Four methods: Paracrine, Autocrine, Endocrine, and Cell-Cell Contact.

  • Signal Transduction: The pathway that begins with ligand-receptor binding, includes intracellular signaling pathways for cellular response.

Cell Cycle Summary

  1. Interphase: Cell grows and replicates DNA (G1, S, G2 phases).

  2. Mitosis: Division of the nucleus (Prophase, Prometaphase, Metaphase, Anaphase, Telophase).

  3. Cytokinesis: Division of the cytoplasm.

Regulation of Cell Cycle

  • Control mechanisms include checkpoint systems that ensure conditions are favorable for division (G1, G2, M checkpoints).

Links provide context regarding signaling pathways and cell cycle dynamics.

Sample Cell Communication and Cell Cycle Questions

  1. Interphase Includes:    - Correct Answer: C. S, G1, and G2 phases only.

  2. First Step in Mitosis:    - Correct Answer: A. Chromatin condenses into chromosomes.

  • Unit 5

Heredity

Overview

  • Covers approximately 8–11% of questions.

Meiosis

  • Process that results in gamete formation.

  • Has two divisions: Meiosis I (homologous chromosomes separate) and Meiosis II (sister chromatids separate).

Genetic Diversity

  • Generated through Independent Assortment, Crossing Over, and Random Fertilization.

Mendel’s Laws

  1. Law of Segregation: Allele pairs separate during gamete formation.

  2. Law of Independent Assortment: Genes are inherited independently of one another.

  3. Law of Dominance: Dominant alleles mask the effects of recessive alleles.

Genotype and Phenotype

  • Genotype: Genetic makeup; Phenotype: Physical characteristics.

  • Use of Punnett squares to predict inheritance patterns and probabilities of traits.

Non-Mendelian Inheritance

  • Includes exceptions like linked genes, X-linked traits, and polygenic traits.

Links provide insights into genetics and inheritance patterns.

Sample Heredity Questions

  1. Heterozygote Phenotype: When intermediate phenotypes occur:    - Correct Answer: B. Incomplete dominance.

  2. Test Cross Purpose: To determine genotype of the dominant phenotype:    - Correct Answer: D. Test cross.

  • Unit 6

Gene Expression and Regulation

Overview

  • Covers approximately 12–16% of questions.

Roles of DNA and RNA

  • DNA: Contains genetic blueprints for protein synthesis.

  • RNA: Involved in translating genetic information into proteins,   - Transcription: DNA to mRNA.   - Translation: mRNA to proteins via tRNA.

Gene Regulation

  • Transcription Factors: Proteins that control gene expression.

  • Operons: Groups of genes regulated together in prokaryotes (e.g., lac operon).

Links provide context on molecular biology techniques and gene control.

Sample Gene Expression and Regulation Questions

  1. Primary Variation for Natural Selection:    - Correct Answer: C. Mutation.

  2. Example of Prokaryotic Organism:    - Correct Answer: C. Bacterium.

  • Unit 7

Natural Selection

Overview

  • Covers approximately 13–20% of questions.

Evolution and Natural Selection

  • Evolution: Change in heritable traits through genetic changes over generations.

  • Natural Selection: Process that enhances reproductive success of advantageous traits.

Evidence for natural selection includes fossil records, comparative anatomy, and genetic data.

Mechanisms of Variation

  • Gene Migration, Genetic Drift, and mutation contribute to population changes.

  • Hardy-Weinberg Equilibrium: Describes allele frequencies under stable conditions.

  • Conditions for Equilibrium: Large population, no migration, no mutations, no selection, random mating.

Links provide further details on evolutionary principles.

Sample Natural Selection Questions

  1. Vestigial Structures: True statement about vestigial structures?    - Correct Answer: C. They may be useless.

  2. Oparin-Haldane Hypothesis: Early Earth had a reducing atmosphere because?    - Correct Answer: B. Oxygen was absent.

  3. Diverse Species Formation: What describes many diverse species arising from a single species?    - Correct Answer: C. Adaptive radiation.

  • Unit 8

Ecology

Overview

  • Covers approximately 10–15% of questions.

Ecology Definitions

  • Organisms: Individuals of a species with adaptations for environment.

  • Populations: Groups of organisms living together; studied through size, density, and structure analysis.

  • Communities: All populations in a given area; interactions shape community structures.

  • Ecosystems: Communities plus their non-living environment; focus on energy flow and nutrient cycling.

  • Biosphere: Global level, including interactions across all ecosystems.

Links provide additional studies on ecology and species interaction dynamics.

Sample Ecology Questions

  1. Example of Density-Dependent Factor:    - Correct Answer: C. Scarcity of food.

  2. Factors in Population Dynamics:    - Correct Answer: A. The birth and death rates influence population change.

Thank you for utilizing this AP Biology study guide. For in-depth understanding, consider engaging with the hyperlinks provided for further study materials and resources.