🧬AP Biology AP Cram Sessions 2020

Key Concepts and Theories

• Cell theory states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells
• Gene theory proposes that genes are the functional units of heredity, are located on chromosomes, and consist of DNA
• Evolution by natural selection explains how populations change over time due to genetic variation, differential reproduction, and inheritance of favorable traits
• Homeostasis maintains stable internal conditions in an organism through various feedback mechanisms (thermoregulation)
• Structure and function are correlated at all levels of biological organization from molecules to ecosystems
  • Enzymes have specific active sites that bind to substrates, lowering the activation energy of reactions
• Energy flows through ecosystems from producers to consumers and decomposers, while nutrients cycle between biotic and abiotic components
• DNA replication, transcription, and translation are the central dogma of molecular biology, explaining how genetic information is stored, copied, and expressed

Biological Processes and Systems

• Photosynthesis converts light energy into chemical energy (glucose) in plants and other autotrophs, releasing oxygen as a byproduct
  • Light-dependent reactions occur in thylakoid membranes and produce ATP and NADPH
  • Light-independent reactions (Calvin cycle) use ATP and NADPH to fix carbon dioxide into organic compounds
• Cellular respiration breaks down organic molecules to release energy (ATP) in the presence of oxygen
  • Glycolysis occurs in the cytoplasm and produces a small amount of ATP
  • Citric acid cycle takes place in the mitochondrial matrix, generating high-energy electrons for the electron transport chain
  • Oxidative phosphorylation involves the electron transport chain and chemiosmosis to produce the majority of ATP
• Cell cycle consists of interphase (G1, S, G2) and mitosis (prophase, metaphase, anaphase, telophase) leading to cell division
• Meiosis produces haploid gametes through two rounds of cell division, introducing genetic variation via crossing over and independent assortment
• Mendelian genetics involves the inheritance of discrete traits controlled by single genes (Mendel's pea plant experiments)
• Nervous system transmits signals through neurons via electrical impulses (action potentials) and chemical synapses (neurotransmitters)
• Immune system defends against pathogens using innate (non-specific) and adaptive (specific) responses
  • Humoral immunity involves B cells producing antibodies to neutralize antigens
  • Cell-mediated immunity involves T cells directly attacking infected or cancerous cells

Important Experiments and Studies

• Griffith's experiment demonstrated the transformation of bacteria, suggesting the existence of a "transforming principle" later identified as DNA
• Avery, MacLeod, and McCarty's experiments confirmed that DNA, not proteins, was the genetic material responsible for transformation
• Hershey and Chase's phage experiments using radioactive labeling showed that DNA, not protein, enters bacterial cells during infection
• Meselson and Stahl's experiment using heavy nitrogen isotopes provided evidence for the semiconservative replication of DNA
• Miller and Urey's experiment simulated early Earth conditions, producing amino acids and suggesting a possible origin of life scenario
• Watson and Crick's discovery of the double helix structure of DNA, based on Franklin's X-ray crystallography data, revolutionized our understanding of genetics
• Mendel's pea plant experiments uncovered the fundamental principles of inheritance, including the concepts of dominant and recessive alleles, segregation, and independent assortment

Diagrams and Visual Aids

• Cell structure diagrams illustrate the major organelles and their functions in eukaryotic cells (nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus)
• Punnett squares are used to predict the probability of genotypes and phenotypes in genetic crosses
• Pedigree charts depict the inheritance of traits within families across generations
• Phylogenetic trees represent evolutionary relationships among species based on shared derived characteristics
• Food webs and energy pyramids demonstrate the flow of energy and matter through trophic levels in ecosystems
• Action potential graphs show the changes in membrane potential during the depolarization and repolarization of neurons
• Karyotypes display the number and appearance of chromosomes in a cell, used to identify chromosomal abnormalities (Down syndrome)

Equations and Calculations

• Hardy-Weinberg equation ($p^2 + 2pq + q^2 = 1$) predicts genotype frequencies in populations at genetic equilibrium
  • $p$ represents the frequency of the dominant allele, and $q$ represents the frequency of the recessive allele
• Population growth equations, such as exponential growth ($dN/dt = rN$) and logistic growth ($dN/dt = rN(1-N/K)$), model changes in population size over time
• Chi-square ($\chi^2$) test is used to determine if observed data deviate significantly from expected values in genetic crosses or population studies
• Mendelian inheritance ratios (3:1 for monohybrid crosses, 9:3:3:1 for dihybrid crosses) predict the expected phenotypic outcomes of genetic crosses
• Standard deviation ($\sigma = \sqrt{\frac{\sum(x - \mu)^2}{n}}$) measures the dispersion of data points from the mean in a population

Lab Techniques and Procedures

• Microscopy (light, electron) allows for the observation of cells, tissues, and microorganisms at various magnifications
• Gel electrophoresis separates DNA, RNA, or proteins based on size and charge, often used in DNA fingerprinting or protein analysis
• Polymerase chain reaction (PCR) amplifies specific DNA sequences using primers, DNA polymerase, and thermal cycling
• Spectrophotometry measures the absorption of light by a sample, used to quantify the concentration of biomolecules (DNA, proteins)
• Chromatography (paper, thin-layer, column) separates mixtures based on the differential solubility of components in a mobile and stationary phase
• Enzyme-linked immunosorbent assay (ELISA) detects the presence of specific antigens or antibodies in a sample using antibody-enzyme conjugates
• Gram staining differentiates bacteria based on cell wall composition (gram-positive vs gram-negative)

Common Exam Questions

• Describe the structure and function of the major macromolecules in living organisms (carbohydrates, lipids, proteins, nucleic acids)
• Compare and contrast the processes of mitosis and meiosis, including their roles in the cell cycle and reproduction
• Explain the concept of gene expression, including the roles of transcription factors and post-transcriptional modifications
• Discuss the evidence supporting the theory of evolution by natural selection, such as fossil records, comparative anatomy, and molecular homology
• Analyze the relationship between structure and function in the human respiratory and circulatory systems
• Predict the outcomes of genetic crosses using Mendel's laws of inheritance and Punnett squares
• Describe the process of DNA replication, including the roles of enzymes such as DNA polymerase and helicase

Study Tips and Strategies

• Create concept maps or flowcharts to visualize connections between related topics and processes
• Use mnemonic devices to memorize key terms, processes, or sequences (King Philip Came Over For Good Soup for taxonomic hierarchy)
• Practice drawing and labeling diagrams of important structures or processes (cell organelles, stages of mitosis)
• Work through practice problems and past exam questions to familiarize yourself with the types of questions asked and to identify areas for improvement
• Teach complex concepts to a classmate or study partner to reinforce your understanding and identify gaps in your knowledge
• Break down large amounts of information into smaller, manageable chunks and focus on one topic at a time
• Utilize active recall techniques, such as flashcards or self-quizzing, to test your knowledge and retention of key concepts
• Seek help from your teacher, tutor, or study group when you encounter difficult concepts or need clarification