AP Biology – Semester 1 Final Exam Study Guide

AP Biology – Semester 1 Final Exam Study Guide

This study guide outlines all major content areas and skills assessed on the Semester 1 Final Exam.

I. Cell Structure & Function

  • Prokaryotic vs. Eukaryotic Cells

    • Definition: Prokaryotic cells lack a nucleus and membrane-bound organelles whereas eukaryotic cells have both.

    • Examples: Prokaryotic cells include bacteria and archaea, while eukaryotic cells include plant, animal, fungal, and protist cells.

  • Functions of Major Organelles

    • Nucleus: Stores genetic material and coordinates cell activities such as growth and reproduction.

    • Ribosomes: Sites of protein synthesis, found free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (ER).

    • Rough Endoplasmic Reticulum (RER): Studded with ribosomes; involved in protein synthesis and processing.

    • Smooth Endoplasmic Reticulum (SER): Synthesizes lipids, metabolizes carbohydrates, and detoxifies drugs.

    • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

    • Lysosomes: Contain enzymes for digestion; breakdown of waste materials and cellular debris.

    • Vacuoles: Storage sacs that hold various substances; large central vacuole in plant cells maintains turgor pressure.

    • Peroxisomes: Contain enzymes that oxidize fatty acids and amino acids; detoxify harmful substances.

    • Mitochondria: Powerhouse of the cell; site of ATP (energy) production through cellular respiration.

    • Chloroplasts: Site of photosynthesis in plant cells; contain chlorophyll and convert light energy into chemical energy.

    • Structure-Function Relationships: The structure of each organelle relates directly to its function (e.g. the double membrane of mitochondria facilitates ATP generation).

  • Endosymbiotic Theory and Supporting Evidence

    • Definition: The theory that eukaryotic cells evolved from a symbiotic relationship between prokaryotic cells.

    • Evidence: Similarities between mitochondria/chloroplasts and prokaryotes, double membranes, own DNA, and ribosomes.

  • Surface Area-to-Volume Ratio

    • Definition: A measurement that describes how much surface area is available relative to the volume of an object.

    • Importance: Higher ratios allow for more efficient exchange of materials; cells optimize this ratio to maximize metabolic efficiency.

  • Cell Size and Shape

    • Relation to Diffusion and Material Exchange: Smaller cells generally have an easier and more efficient time with diffusion due to a larger surface area-to-volume ratio.

  • Differences Among Plant, Animal, Fungal, and Bacterial Cells

    • Plant Cells: Have a cell wall, chloroplasts, and large central vacuoles.

    • Animal Cells: No cell wall, usually have smaller vacuoles.

    • Fungal Cells: Have cell walls made of chitin, unique cellular structure.

    • Bacterial Cells: Lack nucleus and organelles, characterized by peptidoglycan cell walls.

  • Cell Walls: Composition and Function Across Kingdoms

    • Plant Cell Walls: Composed primarily of cellulose; provide structure and support.

    • Fungal Cell Walls: Composed of chitin; gives rigidity.

    • Bacterial Cell Walls: Composed of peptidoglycan; essential for survival and shape.

II. Membrane Structure & Transport

  • Phospholipid Bilayer Structure and Properties

    • Composition: Two layers of phospholipids with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward.

    • Properties: Semi-permeable, allowing selective transfer of substances.

  • Hydrophilic vs. Hydrophobic Regions of Membranes

    • Hydrophilic Regions: Attracted to water, form the exterior of the membrane.

    • Hydrophobic Regions: Repel water, form the interior of the membrane, affecting permeability.

  • Membrane Proteins and Their Functions

    • Types: Integral (span the membrane) and peripheral (sit on the surface).

    • Functions: Transport, receptor activity, cell recognition, and signaling.

  • Passive Transport

    • Diffusion: Movement of molecules from an area of higher concentration to lower concentration.

    • Facilitated Diffusion: Passive transport aided by membrane proteins.

    • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Active Transport and ATP Use

    • Definition: Movement of substances against their concentration gradient; requires energy (ATP).

    • Examples: Sodium-potassium pump, proton pump.

  • Electrochemical Gradients

    • Definition: A gradient that combines both the concentration gradient and the electric potential across a membrane; crucial for processes like nerve impulses.

  • Water Potential and Movement of Water in Cells

    • Concept: Water potential determines the direction of water movement across cell membranes.

  • Tonicity

    • Definitions:

    • Hypotonic Solution: Lower solute concentration compared to the cell; may cause swelling.

    • Hypertonic Solution: Higher solute concentration than the cell; may cause shrinking.

    • Isotonic Solution: Equal solute concentration between the cell and solution; stable condition.

  • Dialysis Tubing Experiments as Membrane Models

    • Used to demonstrate selectively permeable membranes and the principles of diffusion and osmosis in a controlled environment.

III. Enzyme Structure & Function

  • Enzyme Specificity and Active Sites

    • Definition: Enzymes are highly specific in the substrates they bind; the active site is the region where substrate molecules bind to the enzyme.

  • Induced Fit Model

    • Explanation: The active site of an enzyme changes shape to better fit the substrate upon binding, enhancing catalysis.

  • Effects of Temperature and pH on Enzyme Activity

    • Temperature: Each enzyme has an optimal temperature; deviations can lead to decreased activity or denaturation.

    • pH: Each enzyme also has an optimal pH range; outside this range, activity can be harmed.

  • Enzyme Denaturation

    • Definition: Loss of enzyme structure (and function) due to extreme conditions (high temperature, extreme pH), leading to an inactive enzyme.

  • Role of Enzymes in Metabolism

    • Enzymes catalyze biochemical reactions, lowering the activation energy needed for those reactions.

  • Relationship Between Structure and Function in Proteins

    • The shape of a protein is directly related to its function; changes in structure can significantly impact activity.

  • Tertiary Protein Structure and R-group Interactions

    • Tertiary structure is determined by interactions among various side chains (R-groups) of amino acids, resulting in a 3D shape critical for function.

IV. Cellular Energetics

  • ATP Structure and Function

    • Structure: Composed of adenine, ribose, and three phosphate groups.

    • Function: ATP serves as the primary energy currency of the cell, releasing energy when phosphate groups are hydrolyzed.

  • Chemiosmosis and Electron Transport Chains

    • Chemiosmosis: Process where ATP is synthesized using the proton gradient created by electron transport chains in mitochondria and chloroplasts.

  • Cellular Respiration Overview

    • Glycolysis: Breakdown of glucose into pyruvate, producing ATP and NADH. Occurs in the cytoplasm.

    • Citric Acid Cycle (Krebs Cycle): Occurs in mitochondria; processes pyruvate to produce more NADH and FADH2, releasing CO2.

    • Oxidative Phosphorylation: Utilizes electron transport chains and chemiosmosis to produce ATP; requires oxygen.

  • Oxygen’s Role in Aerobic Respiration

    • Oxygen is the final electron acceptor in the electron transport chain, essential for producing ATP in aerobic conditions.

  • Photosynthesis Overview

    • Light-Dependent Reactions: Convert light energy into chemical energy, producing ATP and NADPH. Occur in the thylakoid membranes of chloroplasts.

    • Calvin Cycle: Uses ATP and NADPH to convert CO2 into glucose; occurs in the stroma of chloroplasts.

  • Inputs and Outputs of Photosynthesis and Respiration

    • Photosynthesis:

    • Inputs: Solar energy, water, CO2

    • Outputs: Glucose, oxygen

    • Cellular Respiration:

    • Inputs: Glucose, oxygen

    • Outputs: CO2, water, ATP

  • Relationship Between Respiration and Photosynthesis

    • They are interconnected; the products of one are the reactants of the other, creating a cycle crucial for life.

V. Cell Communication & Signal Transduction

  • Types of Signaling

    • Autocrine: Cells respond to signals they produce themselves.

    • Paracrine: Cells communicate with nearby cells through signals.

    • Endocrine: Hormones are secreted into the bloodstream to affect distant cells.

    • Juxtacrine: Direct communication through cell-to-cell contact.

  • Ligands and Receptors

    • Ligands: Signal molecules that bind to receptors.

    • Receptors: Proteins that bind to ligands, initiating a cellular response.

  • Cell-Surface vs. Intracellular Receptors

    • Cell-Surface Receptors: Bind to hydrophilic ligands and trigger signal transduction pathways.

    • Intracellular Receptors: Bind to hydrophobic ligands that can cross the plasma membrane and activate directly in the cell.

  • Signal Transduction Pathways

    • Series of events initiated by the binding of a ligand to a receptor, resulting in a cellular response.

  • Second Messengers (e.g., cAMP)

    • Small molecules that relay signals inside the cell after activation by a receptor; amplify the strength of the signal.

  • Amplification of Signals

    • Process by which a small signal leads to a large response in the cell, often involving second messengers and cascade reactions.

  • Feedback Mechanisms (Positive vs. Negative)

    • Positive Feedback: Response enhances the signal (e.g., childbirth).

    • Negative Feedback: Response diminishes the signal, maintaining homeostasis (e.g., blood glucose regulation).

  • Hormonal Signaling Examples (e.g., Insulin, Epinephrine)

    • Insulin: Regulates glucose uptake and lowers blood glucose levels.

    • Epinephrine: Increases heart rate and energy availability during stress (fight-or-flight response).

VI. Cell Cycle, Mitosis & Apoptosis

  • Phases of the Cell Cycle

    • G1 Phase: Cell grows and conducts normal metabolic activities.

    • S Phase: DNA is replicated.

    • G2 Phase: Preparation for mitosis, further growth.

    • M Phase: Mitosis and cytokinesis occur, resulting in cell division.

  • Mitosis Stages and Their Purposes

    • Prophase: Chromatin condenses into chromosomes; nuclear envelope breaks down.

    • Metaphase: Chromosomes line up at the metaphase plate.

    • Anaphase: Sister chromatids are pulled apart toward opposite poles.

    • Telophase: Nuclear envelopes reform; chromosomes de-condense.

  • Cytokinesis

    • Definition: Division of the cytoplasm, resulting in two daughter cells.

    • Mechanism: In animal cells, a cleavage furrow forms; in plant cells, a cell plate forms.

  • Cell Cycle Checkpoints

    • Control mechanisms that ensure the proper division of the cell; include G1, G2, and M checkpoints.

  • Regulation of the Cell Cycle

    • Involves cyclins and cyclin-dependent kinases (CDKs) that regulate progression through the cycle.

  • Apoptosis and Its Cellular Mechanisms

    • Programmed cell death that is vital for development and maintaining homeostasis.

    • Mechanisms include caspase activation and DNA fragmentation.

  • Consequences of Cell Cycle Disruption

    • Can lead to uncontrolled cell growth or cancer.

VII. Meiosis & Genetic Variation

  • Purpose of Meiosis

    • To produce gametes (sperm and eggs) with half the genetic material for sexual reproduction, increasing genetic diversity.

  • Stages of Meiosis I and Meiosis II

    • Meiosis I: Homologous chromosomes separate; generates two haploid cells.

    • Meiosis II: Sister chromatids separate; produces four haploid gametes.

  • Synapsis and Crossing Over

    • Synapsis: Pairing of homologous chromosomes during Prophase I.

    • Crossing Over: Exchange of genetic material between homologous chromosomes, contributing to genetic diversity.

  • Independent Assortment

    • The random distribution of maternal and paternal chromosomes during meiosis, resulting in genetic variation in gametes.

  • Nondisjunction and Chromosomal Abnormalities

    • Nondisjunction: Failure of chromosomes to separate properly during meiosis, leading to an abnormal number of chromosomes in gametes (e.g., Down syndrome).

  • Comparison of Mitosis and Meiosis

    • Mitosis: Produces two identical diploid cells; involved in growth and repair.

    • Meiosis: Produces four non-identical haploid cells; involved in sexual reproduction.

  • Haploid vs. Diploid Cells

    • Haploid Cells: Contain one set of chromosomes (n), found in gametes.

    • Diploid Cells: Contain two sets of chromosomes (2n), found in somatic cells.

VIII. Mendelian & Non-Mendelian Genetics

  • Dominant and Recessive Alleles

    • Dominant Alleles: Expressed in the phenotype if at least one copy is present.

    • Recessive Alleles: Expressed in the phenotype only if two copies are present.

  • Genotype vs. Phenotype

    • Genotype: The genetic makeup of an organism.

    • Phenotype: The observable characteristics of an organism.

  • Monohybrid and Dihybrid Crosses

    • Monohybrid Cross: Examination of one trait; involves one pair of alleles.

    • Dihybrid Cross: Examination of two traits; involves two pairs of alleles.

  • Independent Assortment

    • Mendel's principle that states alleles for different traits segregate independently of one another during gamete formation.

  • Gene Linkage

    • Genes located close to each other on the same chromosome tend to be inherited together.

  • Sex-Linked Inheritance

    • Genes located on sex chromosomes; often exhibit different inheritance patterns in males and females.

  • Carrier Status and Inheritance Patterns

    • Carriers: Individuals who have one copy of a recessive allele that does not manifest phenotypically but can be passed to offspring.

  • Incomplete Dominance and Codominance

    • Incomplete Dominance: A case where heterozygotes show a blend of traits (e.g., red and white flower producing pink flowers).

    • Codominance: Both alleles are fully expressed in the phenotype (e.g., AB blood type).

  • Interpreting Pedigrees

    • Identifying patterns of inheritance, determining if traits are dominant or recessive, autosomal or sex-linked, and deducing genotypes of individuals based on known phenotypes.

IX. Molecular Biology & Macromolecules

  • Structure and Function of:

    • Carbohydrates: Organic compounds made of carbon, hydrogen, and oxygen; provide energy and structural support (e.g., glucose, cellulose).

    • Lipids: Nonpolar molecules; include fats, oils, and phospholipids. Energy storage, membrane structure, and signaling.

    • Proteins: Comprised of amino acids; perform a variety of functions: catalysis (enzymes), transport, structure, and signaling.

    • Nucleic Acids: DNA and RNA; store and transmit genetic information.

  • Dehydration Synthesis and Hydrolysis

    • Dehydration Synthesis: Reaction that combines monomers into polymers with the release of water.

    • Hydrolysis: Reaction that breaks down polymers into monomers, using water.

  • Relationship Between Molecular Structure and Function

    • The specific arrangement of atoms in molecules determines their properties and functionality in biological systems.

  • Chemical Composition of Macromolecules (Elements, Monomers)

    • Carbohydrates: Composed of C, H, O; monomers are monosaccharides.

    • Lipids: Made of C, H (and sometimes O); no true monomers.

    • Proteins: Composed of C, H, O, N; monomers are amino acids.

    • Nucleic Acids: Composed of C, H, O, N, P; monomers are nucleotides.

X. Experimental Design & Data Analysis

  • Identifying Independent and Dependent Variables

    • Independent Variable: The factor that is manipulated or changed in an experiment.

    • Dependent Variable: The factor that is measured or observed in response to the independent variable.

  • Controls and Constants

    • Controls: Conditions that remain constant throughout the experiment to ensure valid results.

    • Constants: Factors that are kept the same to eliminate confounding variables.

  • Interpreting Tables and Graphs

    • Skills required to understand and analyze data; includes recognizing trends, drawing conclusions, and identifying anomalies.

  • Evaluating Models and Simulations

    • Assessing the reliability and accuracy of scientific models in representing real-world phenomena.

  • Chi-square Goodness-of-Fit Tests

    • Statistical test assessing how well observed data fits expected data.

    • Null Hypothesis: Assumes no significant difference between observed and expected data.

    • Degrees of Freedom: Calculated as the number of categories minus one.

    • How to Find the Critical Value from the Chart: Look up the significance level (e.g., p=0.05) and use the degrees of freedom to find the critical value.

    • Interpreting Results: Determine whether to reject or fail to reject the null hypothesis based on comparison of the calculated value to the critical value.

XI. Evolution & Evidence for Common Ancestry

  • Shared Metabolic Pathways (e.g., Glycolysis)

    • Glycolysis is a common metabolic pathway shared among diverse organisms, indicating a common ancestry.

  • Molecular and Cellular Evidence for Evolution

    • Includes DNA sequence homology, similarities in cellular structure, and metabolic functions.

  • Adaptation and Natural Selection

    • Process where organisms better adapted to their environment tend to survive and produce more offspring; a key mechanism of evolution.

  • Changes in Populations Over Time

    • Observations of populations providing evidence for gradual evolution and speciation.

  • Interpreting Real Biological Data Sets

    • Skills to analyze and draw conclusions from experimental and observational data regarding evolutionary processes.

XII. Plant Structure & Transport

  • Transpiration and Water Movement Due to Capillary Action (Cohesion/Adhesion)

    • Transpiration: Process of water movement through a plant and its evaporation from aerial parts, especially leaves.

    • Cohesion: Attraction between water molecules; allows water to be pulled up through xylem.

    • Adhesion: Attraction between water molecules and the walls of xylem vessels, aiding water movement.

  • Water Potential Gradients in Plants

    • Water potential is a measure of the potential energy in water, driving the movement of water from regions of high to low potential (e.g., from roots to leaves).

Study Tips

  • Focus on processes, not memorization.

  • Be able to explain why biological mechanisms work.

  • Practice interpreting data, graphs, and models.

  • Review vocabulary in context.

  • Connect structure to function whenever possible.