Biology Study Guide: Foundations, Chemistry, Cells, Genetics, and Molecular Biology 2

Chapter 1: Introduction – Evolution and the Foundations of Biology

Scientific Method

The scientific method is a systematic approach used to investigate natural phenomena. It consists of several key steps that ensure objectivity and reproducibility in scientific research.

• Observation: Gathering information about phenomena.

• Hypothesis: A testable statement explaining observations.

• Prediction: Expected outcome if the hypothesis is correct.

• Experiment: Testing the hypothesis under controlled conditions.

• Analysis: Interpreting data to accept or reject the hypothesis.

• Hypothesis vs. Theory: A hypothesis is a specific, testable prediction; a theory is a broad explanation supported by extensive evidence.

• Dependent vs. Independent Variables: The independent variable is manipulated; the dependent variable is measured.

• Controls vs. Treatments: Controls are unchanged for comparison; treatments are experimental conditions.

Example: Testing plant growth under different light conditions.

Unifying Qualities of Life

Life is characterized by several fundamental features and organizational levels.

• Taxonomic Ranks: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Levels of Organization: Molecule → Organelle → Cell → Tissue → Organ → Organism → Population → Community → Ecosystem → Biosphere.

• Emergent Properties: New properties arise at each level due to interactions among components.

• Unifying Features: Cellular organization, metabolism, homeostasis, growth, reproduction, heredity, evolution.

Example: Cells are the basic unit of life; all living things exhibit metabolism.

Chapter 2: The Chemical Context of Life

Atomic Structure and Properties

Atoms are the fundamental units of matter, composed of protons, neutrons, and electrons.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

• Atomic Number: Number of protons; defines the element.

• Isotopes: Atoms with same number of protons, different neutrons.

• Atomic Mass: Sum of protons and neutrons.

• Valence Shells: Outermost electron shell; determines chemical reactivity.

Chemical Bonding

Atoms form bonds to achieve stable electron configurations.

• Ionic Bonds: Transfer of electrons; forms charged ions.

• Polar Covalent Bonds: Unequal sharing of electrons.

• Nonpolar Covalent Bonds: Equal sharing of electrons.

• Metallic Bonds: Electrons shared among many atoms (mainly in metals).

pH and Properties of Water

pH measures hydrogen ion concentration; water exhibits unique properties due to hydrogen bonding.

• pH Scale: Ranges from 0 (acidic) to 14 (basic); logarithmic scale.

• Acid: Releases H+ ions; pH < 7.

• Base: Releases OH- ions; pH > 7.

• Water Properties: Cohesion, adhesion, high specific heat, solvent abilities.

• Hydrogen Bonding: Weak attraction between water molecules; responsible for water's properties.

Example: Water's high heat capacity moderates Earth's climate.

Chapter 3: Carbon and the Molecular Diversity of Life

Functional Groups

Functional groups are specific groups of atoms within molecules that determine chemical properties.

• Hydroxyl (-OH): Polar.

• Carbonyl (C=O): Polar.

• Carboxyl (-COOH): Acidic, negatively charged.

• Amine (-NH2): Basic, positively charged.

• Phosphate (-PO4): Negatively charged.

• Sulfhydryl (-SH): Nonpolar.

• Methyl (-CH3): Nonpolar.

Macromolecules

Macromolecules are large biological molecules essential for life.

• Carbohydrates: Monomers are monosaccharides; polymers are polysaccharides.

• Proteins: Monomers are amino acids; polymers are polypeptides.

• Lipids: Glycerol and fatty acids form fats, phospholipids, cholesterol.

• Nucleic Acids: DNA and RNA; monomers are nucleotides.

Example: Starch (a polysaccharide) is a storage carbohydrate in plants.

Chapter 4: A Tour of the Cell

Eukaryotic Organelles and Functions

Eukaryotic cells contain membrane-bound organelles, each with specialized functions.

• Nucleus: Contains genetic material; site of transcription.

• Endoplasmic Reticulum (ER): Smooth ER synthesizes lipids; rough ER has ribosomes for protein synthesis.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Vesicles/Vacuoles: Storage and transport.

• Cell Membrane: Selective barrier; present in all domains.

• Cell Wall: Structural support; found in plants, fungi, bacteria.

• Chloroplasts: Photosynthesis; found in plants and algae.

• Mitochondria: Cellular respiration; found in most eukaryotes.

Example: Animal cells lack cell walls and chloroplasts; plant cells have both.

Chapter 5: Membrane Transport and Cell Signaling

Membrane Structure and Function

Cell membranes are dynamic structures composed of lipids and proteins.

• Membrane Coherence: Maintained by hydrophobic interactions among phospholipids.

• Fluidity: Influenced by temperature, fatty acid chain length, saturation, and cholesterol.

• Proteins: Serve as channels, carriers, receptors, and enzymes.

Transport Mechanisms

• Simple Diffusion: Movement of molecules from high to low concentration.

• Facilitated Diffusion: Uses membrane proteins; no energy required.

• Osmosis: Diffusion of water across a membrane.

• Active Transport: Requires energy (ATP) to move substances against concentration gradient.

Example: Sodium-potassium pump is an active transport mechanism.

Chapter 6: An Introduction to Metabolism

Thermodynamics and Metabolism

Metabolism encompasses all chemical reactions in an organism, governed by thermodynamic laws.

• First Law: Energy cannot be created or destroyed.

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

• Anabolic: Building molecules; requires energy.

• Catabolic: Breaking down molecules; releases energy.

• Exergonic: Releases energy; spontaneous.

• Endergonic: Requires energy; non-spontaneous.

• Hydration/Hydrolysis: Addition/removal of water in reactions.

• ATP: Main energy currency of the cell.

Enzymes and Regulation

• Enzymes: Biological catalysts; speed up reactions.

• Cofactors: Non-protein helpers (metal ions, vitamins).

• Competitive Inhibitors: Bind active site, block substrate.

• Noncompetitive Inhibitors: Bind elsewhere, change enzyme shape.

• Activators: Increase enzyme activity.

Example: ATP synthase is an enzyme involved in cellular respiration.

Chapter 7: Cellular Respiration and Fermentation

Chemical Equations and Processes

Cellular respiration converts glucose into ATP; fermentation occurs in absence of oxygen.

• Aerobic Respiration: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \text{ATP}$

• Anaerobic Fermentation: $\text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 + \text{ATP}$ (alcohol); $\text{C}_6\text{H}_{12}\text{O}_6 \rightarrow 2\text{C}_3\text{H}_6\text{O}_3 + \text{ATP}$ (lactic acid)

• Reduction: Gain of electrons.

• Oxidation: Loss of electrons.

Cellular Locations and Steps

• Glycolysis: Cytoplasm; produces 2 ATP.

• Fermentation: Cytoplasm; produces 2 ATP.

• Pyruvate Oxidation: Mitochondrial matrix.

• Krebs Cycle: Mitochondrial matrix; produces 2 ATP.

• Electron Transport Chain: Inner mitochondrial membrane; produces ~34 ATP.

Example: Yeast performs alcohol fermentation; animals perform lactic acid fermentation.

Chapter 8: Photosynthesis

Chemical Equations and Evolutionary Origins

Photosynthesis converts light energy into chemical energy; chloroplasts and mitochondria originated via endosymbiosis.

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

• Chloroplasts: Originated from cyanobacteria.

• Mitochondria: Originated from proteobacteria.

Light Reactions and Calvin Cycle

• Light Reactions: Occur in thylakoid membrane; inputs: light, water, NADP+, ADP + Pi; outputs: NADPH, ATP, O2.

• Calvin Cycle: Occurs in stroma; inputs: CO2, NADPH, ATP; outputs: glucose, water, NADP+, ADP + Pi.

• Photosystem I & II: Capture light energy; drive electron transport.

• Electron Transport Chains: Generate chemiosmotic gradient for ATP synthesis.

Example: Light reactions produce ATP and NADPH for the Calvin cycle.

Comparison: Both photosynthesis and cellular respiration use electron transport chains and chemiosmosis, but differ in direction and products.

Chapters 9 & 10: The Cell Cycle, Mitosis, and Meiosis

Cell Division Concepts

Cells divide by mitosis (for growth and repair) or meiosis (for sexual reproduction).

• Haploid (n): One set of chromosomes.

• Diploid (2n): Two sets of chromosomes.

• Mitosis: Produces identical clones; phases: prophase, metaphase, anaphase, telophase.

• Meiosis: Produces genetically unique gametes; two divisions: Meiosis I (homologous chromosomes separate), Meiosis II (sister chromatids separate).

• Spindles, Microtubules, Centrosomes: Organize chromosome movement.

• Cytokinesis: Animal cells (no cell wall) use cleavage furrow; plant cells (with cell wall) use cell plate.

• Binary Fission: Prokaryotic cell division.

Example: Ferns have centrosomes; flowering plants do not.

Chapter 11: Mendel and the Gene Idea

Genetics Practice and Concepts

Mendelian genetics explains inheritance patterns using Punnett squares and pedigrees.

• Punnett Squares: Visualize allele combinations.

• One-gene and Two-gene Systems: Analyze inheritance of single or multiple traits.

• Dominant vs. Recessive: Dominant alleles mask recessive; recessive can skip generations.

• Pedigrees: Track inheritance in families.

• Codominance: Both alleles expressed (e.g., AB blood type).

• Incomplete Dominance: Intermediate phenotype (e.g., pink flowers).

• Polygenic Inheritance: Multiple genes affect trait.

• Pleiotropy: One gene affects multiple traits.

Example: Sickle cell anemia is pleiotropic.

Chapter 12: The Chromosomal Basis of Inheritance

Sex Chromosomes, Linkage, and Non-nuclear Inheritance

Inheritance patterns are influenced by chromosome structure and gene location.

• Mammalian/Fruit Fly Sex Chromosomes: X and Y; autosomes are non-sex chromosomes.

• X-linked Traits: More common in males; can be dominant or recessive.

• Y-linked Traits: Passed father to son.

• Barr Bodies: Inactivated X chromosome in females.

• Gene Linkage: Genes on same chromosome inherited together; crossing over can separate them.

• Chromosomal Maps: Show gene positions and recombination frequencies.

• Nondisjunction: Failure of chromosomes to separate; leads to aneuploidy.

• Non-nuclear Traits: Mitochondria and chloroplasts inherited maternally.

Example: Color blindness is X-linked recessive.

Chapter 13: The Molecular Basis of Inheritance

Viruses and DNA Replication

Viruses are non-cellular entities that replicate using host machinery; DNA replication is a complex, highly regulated process.

• Viruses: Consist of genetic material (DNA or RNA) and protein coat; infect host cells.

• DNA Nucleotides: Pair via hydrogen bonds (A-T, G-C).

• Chargaff’s Rules: %A = %T, %G = %C.

• 3’ and 5’ Ends: DNA strands are antiparallel; replication proceeds 5’ to 3’.

• Replication Forks/Bubbles: Sites where DNA unwinds for replication.

• Proteins in Replication: Helicase (unwinds), primase (lays primer), DNA polymerases (synthesize DNA), ligase (joins fragments).

• DNA Polymerases: Three main types in eukaryotes; each with specific roles.

• Telomeres: Protect chromosome ends; shorten with each division.

Example: DNA polymerase III synthesizes new DNA strands.

Chapter 14: Gene Expression: From Gene to Protein

Transcription, Translation, and Mutations

Gene expression involves transcription (DNA to RNA) and translation (RNA to protein); mutations alter genetic information.

• Transcription: RNA polymerase synthesizes mRNA from DNA in nucleus.

• Translation: Ribosomes synthesize proteins from mRNA in cytoplasm.

• Genetic Code: Redundant (multiple codons per amino acid), specific (each codon codes for one amino acid).

• Practice: Convert DNA → mRNA → tRNA → amino acids using codon tables.

• Mutations:

  • Silent: No change in amino acid.

  • Missense: Changes one amino acid.

  • Nonsense: Creates stop codon.

  • Chromosomal Rearrangements: Deletions, insertions, inversions, translocations, polyploidy.

Example: Sickle cell mutation is a missense mutation.

Functional Group	Polarity	Charge	Acid/Base
Hydroxyl	Polar	Neutral	Neither
Carbonyl	Polar	Neutral	Neither
Carboxyl	Polar	Negative	Acid
Amine	Polar	Positive	Base
Phosphate	Polar	Negative	Acid
Sulfhydryl	Nonpolar	Neutral	Neither
Methyl	Nonpolar	Neutral	Neither

Additional info: This table summarizes the chemical properties of key functional groups relevant to biological macromolecules.