Cumulative Biology Final Study Guide: Core Concepts and Integrative Themes (Chapters 1–16, 26)

The Science of Biology

Characteristics and Organization of Life

• Life Characteristics: All living things exhibit cellular organization, complexity, sensitivity to stimuli, growth and reproduction, energy use, homeostasis, and evolutionary adaptation.

• Biological Hierarchy: Life is organized from atoms → molecules → organelles → cells → tissues → organs → organ systems → organisms → populations → ecosystems → biosphere.

Scientific Inquiry

• Scientific Method: Involves observation, hypothesis formation, experimentation, data collection, and drawing conclusions.

• Reasoning: Deductive (general to specific) and inductive (specific to general) reasoning are used to develop and test hypotheses.

• Theories vs. Laws: Theories are well-supported, interconnected explanations; laws describe universal relationships but do not explain them.

The Chemical Context of Life

Atoms, Elements, and Bonds

• Atoms: Composed of protons, neutrons, and electrons. Isotopes differ in neutron number; ions have gained or lost electrons.

• Chemical Bonds:

  • Ionic Bonds: Transfer of electrons between atoms.

  • Covalent Bonds: Sharing of electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

  • Hydrogen Bonds: Weak attractions between polar molecules, especially important in water and biological macromolecules.

  • Van der Waals Interactions: Weak, transient attractions between molecules.

• Atomic Number vs. Mass Number: Atomic number = protons; mass number = protons + neutrons.

• Electron Shells: 2-8-8 rule describes the filling of electron shells.

Water and pH

• Properties of Water: Cohesion, adhesion, high specific heat, high heat of vaporization, excellent solvent, hydrophobic interactions, and lower density as ice.

• pH Scale: Measures hydrogen ion concentration; acids donate H+, bases accept H+. Buffers stabilize pH.

• Negative Feedback: Maintains homeostasis, e.g., pH regulation.

Carbon and the Molecular Diversity of Life

Organic Molecules and Functional Groups

• Carbon: Forms four covalent bonds, allowing for diverse organic molecules.

• Functional Groups: Specific groups of atoms (e.g., hydroxyl, carboxyl, amino, phosphate) confer unique properties to molecules.

The Structure and Function of Large Biological Molecules

Macromolecules

• Carbohydrates: Monosaccharides (e.g., glucose), disaccharides, polysaccharides (starch, glycogen for storage; cellulose, chitin for structure).

• Lipids: Triglycerides (saturated/unsaturated), phospholipids (form bilayers), steroids, waxes. Not true polymers.

• Proteins: Polymers of amino acids (20 types), joined by peptide bonds. Four levels of structure: primary, secondary, tertiary, quaternary. Denaturation disrupts structure; chaperones assist folding.

• Nucleic Acids: DNA and RNA are polymers of nucleotides (A, G = purines; C, U, T = pyrimidines). ATP is the energy currency.

A Tour of the Cell

Cell Structure and Function

• Prokaryotes: Lack nucleus and membrane-bound organelles; DNA is circular.

• Eukaryotes: Have nucleus, membrane-bound organelles, and cytoskeleton. Endomembrane system includes ER, Golgi, lysosomes, etc.

• Endosymbiosis: Mitochondria and chloroplasts originated from symbiotic bacteria.

• Cell Walls: Plants (cellulose), fungi (chitin), bacteria (peptidoglycan).

• Cell Junctions: Tight, adhesive, gap junctions (animals); plasmodesmata (plants).

Membrane Structure and Function

Membrane Models and Transport

• Fluid Mosaic Model: Membrane is a dynamic structure of phospholipids, proteins, and cholesterol.

• Transport Mechanisms:

  • Passive Transport: Diffusion, osmosis, facilitated diffusion (channels/carriers).

  • Active Transport: Requires ATP (e.g., Na+/K+ pump, coupled transport).

  • Bulk Transport: Endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis.

• Tonicity: Hypertonic, hypotonic, isotonic solutions affect water movement.

An Introduction to Metabolism

Energy, Thermodynamics, and Enzymes

• First Law of Thermodynamics: Energy cannot be created or destroyed.

• Second Law of Thermodynamics: Entropy (disorder) increases in spontaneous processes.

• Free Energy (ΔG):

  • Spontaneous if ΔG < 0; nonspontaneous if ΔG > 0.

  • Equation: $\Delta G = \Delta H - T\Delta S$

• Enzymes: Biological catalysts that lower activation energy, have specificity, and can be regulated (competitive/noncompetitive inhibitors, allosteric regulation, cofactors/coenzymes).

• ATP Cycle: $\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i}$ releases energy for cellular work.

Cellular Respiration and Fermentation

Stages of Aerobic Respiration

• Glycolysis: Occurs in cytosol; 1 glucose → 2 pyruvate, 2 ATP, 2 NADH.

• Pyruvate Oxidation: In mitochondrial matrix; pyruvate → acetyl-CoA, NADH, CO2.

• Citric Acid Cycle: Acetyl-CoA → 3 NADH, 1 FADH2, 1 ATP, CO2 per turn.

• Electron Transport Chain (ETC) & Chemiosmosis: Inner mitochondrial membrane; proton gradient drives ATP synthase.

• Total ATP Yield: ~36–38 ATP per glucose.

• Anaerobic Respiration: Fermentation regenerates NAD+ (produces lactate or ethanol).

• Regulation: ATP and NADH inhibit key enzymes (feedback inhibition).

Photosynthesis

Light Reactions and the Calvin Cycle

• Overall Equation: $6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2$

• Light Reactions: Occur in thylakoid membranes; produce ATP, NADPH, and O2 (from water splitting).

• Calvin Cycle: Occurs in stroma; uses ATP and NADPH to fix CO2 into G3P (sugar).

• Photorespiration: Rubisco uses O2 instead of CO2, wasting carbon; C4 and CAM plants have adaptations to minimize this.

Cell Communication

Signaling Mechanisms

• Types of Signals: Direct contact, paracrine, autocrine, endocrine, synaptic.

• Receptors: Intracellular (e.g., steroid hormones) or cell-surface (ion channels, enzyme-linked receptors, GPCRs).

• Second Messengers: cAMP, IP3, DAG, Ca2+.

• Signal Transduction: Reception → transduction → response. RTKs activate kinase cascades; GPCRs activate G proteins and effector enzymes.

The Cell Cycle and Mitosis

Phases and Regulation

• Phases: G1, S, G2, M (mitosis and cytokinesis).

• Checkpoints: G1/S, G2/M, spindle checkpoint ensure proper progression.

• Regulation: Cyclin-dependent kinases (Cdks) and cyclins; MPF triggers mitosis.

• Mitosis Stages: Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.

Meiosis and Sexual Life Cycles

Reduction Division and Genetic Variation

• Meiosis I: Homologous chromosomes separate; crossing over and independent assortment increase genetic diversity.

• Meiosis II: Sister chromatids separate.

• Products: Four genetically distinct haploid gametes.

• Sources of Variation: Crossing over, independent assortment, random fertilization.

• Errors: Nondisjunction leads to aneuploidies (e.g., Down syndrome).

Mendelian Genetics

Inheritance Patterns

• Principles:

  • Segregation: Alleles separate during gamete formation.

  • Independent Assortment: Genes on different chromosomes assort independently.

• Monohybrid Cross: 3:1 phenotype, 1:2:1 genotype ratio.

• Testcross: Cross with homozygous recessive to determine genotype.

• Extensions: Incomplete dominance, codominance, multiple alleles (e.g., ABO blood types), pleiotropy, epistasis, polygenic traits, environmental effects.

The Chromosomal Basis of Inheritance

Chromosomes and Human Genetics

• X-linked Inheritance: Males more likely to express recessive X-linked traits.

• Dosage Compensation: X inactivation (Barr bodies) in females.

• Chromosomal Disorders: Autosomal trisomies (e.g., trisomy 21), sex chromosome aneuploidies (Turner syndrome XO, Klinefelter syndrome XXY).

• Gene Linkage & Mapping: Recombination frequency (in map units) estimates gene distance.

The Molecular Basis of Inheritance

DNA Structure and Replication

• DNA Structure: Double helix, antiparallel strands, complementary base pairing (A–T, G–C).

• Replication: Semiconservative (each new DNA has one old and one new strand; Meselson-Stahl experiment).

• Key Enzymes: Helicase (unwinds), primase (RNA primer), DNA polymerase III (synthesis), DNA polymerase I (primer removal), ligase (joins fragments), topoisomerase (relieves tension).

• Leading vs. Lagging Strand: Lagging strand synthesized in Okazaki fragments.

• Telomeres & Telomerase: Protect chromosome ends from degradation.

• DNA Repair: Mismatch repair, excision repair, photorepair.

Gene Expression: From Gene to Protein

Transcription and Translation

• Central Dogma: DNA → RNA → protein.

• Transcription: Initiation (promoter, RNA polymerase), elongation, termination.

• Eukaryotic mRNA Processing: 5’ cap, poly-A tail, splicing (removal of introns by spliceosome).

• Genetic Code: Triplet, universal, degenerate; start codon (AUG), stop codons (UAA, UAG, UGA).

• Translation: Initiation (small ribosomal subunit, tRNA-Met), elongation (A, P, E sites), termination (release factors).

• Mutations: Point (silent, missense, nonsense), frameshift, trinucleotide repeat expansions, structural variants.

Regulation of Gene Expression

Control Mechanisms in Eukaryotes

• Post-transcriptional: Alternative splicing, RNA editing, miRNA/siRNA (RISC complex).

• Translational & Post-translational: mRNA stability, protein degradation (ubiquitin-proteasome system).

Integrative Themes and Exam Strategies

Key Connections and Common Pitfalls

• Location Matters: Know where processes occur (e.g., transcription in nucleus, translation in cytoplasm, ETC in inner mitochondrial membrane).

• Order of Steps: Processes must occur in correct sequence (e.g., cell communication: reception → transduction → response).

• Inputs vs. Outputs: Distinguish what goes into and comes out of processes (e.g., light reactions produce ATP/NADPH; Calvin cycle uses them).

• Structure vs. Function: Structure determines function (e.g., mitochondria produce ATP, nucleus stores DNA).

• Similar Terms: Do not confuse terms (e.g., transcription ≠ translation, gene ≠ protein).

• Question Analysis: Read carefully for what is being asked; application questions may require deeper understanding.

Table: Comparison of Key Biological Processes

Process	Location	Main Inputs	Main Outputs
Glycolysis	Cytosol	Glucose, 2 ATP, 2 NAD+	2 Pyruvate, 4 ATP (net 2), 2 NADH
Citric Acid Cycle	Mitochondrial Matrix	Acetyl-CoA, NAD+, FAD	CO2, NADH, FADH2, ATP
ETC & Chemiosmosis	Inner Mitochondrial Membrane	NADH, FADH2, O2	ATP, H2O
Light Reactions	Thylakoid Membrane	Light, H2O, NADP+, ADP	O2, ATP, NADPH
Calvin Cycle	Stroma	CO2, ATP, NADPH	G3P (sugar), ADP, NADP+
Transcription	Nucleus (eukaryotes)	DNA, RNA nucleotides	pre-mRNA (processed to mRNA)
Translation	Cytoplasm (ribosomes)	mRNA, tRNA, amino acids	Polypeptide (protein)

Additional Info

• Be able to explain the sequence, location, and regulation of major processes.

• Practice distinguishing similar terms and understanding the consequences of changing the order of steps.

• Review enzyme names and functions for DNA replication, transcription, and translation.