Chapter 1 – Evolution and the Foundations of Biology

Hierarchy of Life

The hierarchy of life organizes biological structures from the largest to the smallest, illustrating increasing complexity and specialization.

• Biosphere: All environments on Earth that support life.

• Ecosystem: All living and nonliving components in a particular area.

• Community: All organisms in an ecosystem.

• Population: All individuals of a species in a specific area.

• Organism: An individual living entity.

• Organ System: Group of organs working together.

• Organ: Structure composed of tissues serving a specific function.

• Tissue: Group of similar cells performing a function.

• Cell: Smallest unit of life capable of all life functions.

• Organelle: Functional components within cells.

• Molecule: Chemical structure consisting of two or more atoms.

• Atom: Smallest unit of matter.

Emergent Properties

Emergent properties are new characteristics that arise at each level of biological organization due to the arrangement and interactions of parts.

• Example: Photosynthesis occurs in chloroplasts, but not in a mixture of chloroplast components.

Cells: The Smallest Unit of Life

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (e.g., bacteria, archaea).

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

DNA and Genetic Information

• DNA (Deoxyribonucleic Acid): The molecule carrying genetic instructions; composed of nucleotides (adenine, thymine, cytosine, guanine) with a sugar-phosphate backbone.

• Gene: A segment of DNA that codes for a protein or RNA molecule.

• Chromosome: DNA packaged with proteins; visible during cell division.

• Gene Expression: The process by which information from a gene is used to synthesize a functional product (protein or RNA).

Energy Flow and Nutrient Cycling

• Energy flows through ecosystems (usually entering as sunlight, exiting as heat).

• Nutrients cycle within ecosystems (e.g., carbon, nitrogen cycles).

Biological Interactions

• Producers: Organisms (e.g., plants) that produce organic molecules from CO2 and sunlight.

• Consumers: Organisms that obtain energy by eating other organisms.

Evolution and Diversity

• Evolution: The process of change over time that has resulted in the diversity of life.

• Accounts for both unity (shared traits) and diversity (adaptations) among organisms.

Three Domains of Life

Natural Selection

• Mechanism of evolution proposed by Charles Darwin.

• Individuals with advantageous traits survive and reproduce more successfully.

The Scientific Process

• Steps: Observation, Question, Hypothesis, Prediction, Experiment, Analysis, Conclusion.

• Hypothesis: Testable explanation for an observation.

• Null Hypothesis: Statement that there is no effect or difference.

• Theory: Broad explanation supported by evidence.

• Variables: Independent (manipulated), Dependent (measured).

• Control Group: Baseline for comparison.

• Experimental Group: Receives the treatment.

• Blind/Double Blind: Reduces bias in experiments.

• Statistics: Used to analyze data; larger sample sizes increase reliability.

• Pseudoscience: Claims lacking scientific support.

• Anecdotal Evidence: Personal stories, not reliable for scientific conclusions.

Chapter 2 – The Chemical Context of Life

Elements and Atoms

• Element: Substance that cannot be broken down by chemical means.

• Atom: Smallest unit of an element; composed of protons, neutrons, and electrons.

• Key Elements in Life: Carbon, Hydrogen, Oxygen, Nitrogen (CHON), plus trace elements.

Atomic Structure and Electron Arrangement

• Electrons are arranged in shells around the nucleus.

• The arrangement determines chemical properties and reactivity.

• Valence Electrons: Electrons in the outermost shell; involved in bonding.

Energy Types

• Energy: Capacity to cause change.

• Potential Energy: Stored energy due to position or structure.

• Kinetic Energy: Energy of motion.

• Thermal Energy: Kinetic energy associated with random movement of atoms.

Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms (e.g., NaCl).

• Covalent Bonds: Sharing of electrons (can be polar or nonpolar).

• Polar Covalent: Unequal sharing due to electronegativity differences (e.g., H2O).

• Nonpolar Covalent: Equal sharing (e.g., O2).

• Hydrogen Bonds: Weak bonds between hydrogen and electronegative atoms (e.g., between water molecules).

• Van der Waals Interactions: Weak attractions due to transient charges.

Electronegativity

• Ability of an atom to attract electrons in a bond.

• Determines polarity of molecules.

Chemical Reactions and Equilibrium

• Reactants: Starting materials.

• Products: Resulting substances.

• Chemical Equilibrium: Forward and reverse reactions occur at the same rate.

Properties of Water

• Polarity: Water is polar due to unequal sharing of electrons.

• Hydrogen Bonding: Leads to cohesion, adhesion, high specific heat, and surface tension.

• Specific Heat: Amount of heat needed to change temperature; water has high specific heat.

• Evaporative Cooling: As water evaporates, it removes heat, cooling surfaces.

• Ice Floats: Solid water is less dense than liquid due to hydrogen bonding.

• Solvent of Life: Water dissolves many substances due to polarity.

• Hydrophilic: Water-loving; substances that dissolve in water.

• Hydrophobic: Water-fearing; substances that do not dissolve in water.

Acids, Bases, and pH

• Acid: Increases H+ concentration in solution.

• Base: Reduces H+ concentration (often increases OH-).

• pH Scale: Measures H+ concentration; ranges from 0 (acidic) to 14 (basic).

• pH Equation: $\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

Chapter 3 – Carbon and the Molecular Diversity of Life

Organic Compounds and Carbon

• Organic Compounds: Compounds containing carbon.

• Hydrocarbons: Molecules consisting only of carbon and hydrogen.

• Carbon forms four covalent bonds, allowing for diverse structures.

Chemical Groups

• Seven important functional groups: Hydroxyl, Carbonyl, Carboxyl, Amino, Sulfhydryl, Phosphate, Methyl.

Macromolecules

• Macromolecules: Large molecules (carbohydrates, lipids, proteins, nucleic acids).

• Polymers: Long chains of monomers.

• Monomers: Building blocks of polymers.

Polymerization Reactions

• Dehydration (Condensation): Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Carbohydrates

• Monosaccharides (simple sugars), disaccharides, polysaccharides (e.g., starch, cellulose).

• Function: Energy storage, structural support.

Lipids

• Fats, phospholipids, steroids.

• Function: Energy storage, membrane structure, signaling.

Proteins

• Amino Acids: Building blocks; differ by side chains (R groups).

• Polypeptides: Chains of amino acids linked by peptide bonds.

• Protein Structure: Primary (sequence), Secondary (alpha helix, beta sheet), Tertiary (3D shape), Quaternary (multiple polypeptides).

• Denaturation: Loss of structure and function due to environmental changes.

Nucleic Acids

• DNA and RNA: Store and transmit genetic information.

• Polynucleotides: Chains of nucleotides.

• Pyrimidines: Cytosine, Thymine, Uracil.

• Purines: Adenine, Guanine.

• Deoxyribose: Sugar in DNA; Ribose: Sugar in RNA.

• Prime (') Notation: Denotes carbon positions in sugar rings.

• Double Helix: Structure of DNA; two antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Structure and Function

• Cell: Basic unit of life; all cells share certain features but can differ greatly.

• Organelles: Specialized structures within eukaryotic cells.

Microscopy

• Light Microscopy: Uses light to view cells; can observe living cells.

• Electron Microscopy: Uses electrons for higher resolution (TEM for internal, SEM for surface).

Cell Fractionation

• Technique to separate cell components for study.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, no membrane-bound organelles, smaller size.

• Eukaryotes: Nucleus, membrane-bound organelles, larger size.

Cellular Structures

• Cytoplasm: Fluid inside the cell, excluding the nucleus.

• Plant vs. Animal Cells: Plant cells have cell walls, chloroplasts, and central vacuoles; animal cells do not.

Surface Area to Volume Ratio

• Limits cell size; smaller cells have a higher ratio, facilitating exchange of materials.

Biological Membranes

• Main Component: Phospholipids form the plasma membrane.

• Plasma Membrane: Selectively permeable barrier around the cell.

Endomembrane System

• Includes nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, plasma membrane.

• Involved in synthesis, modification, and transport of proteins and lipids.

Protein Secretion Pathway

• Proteins synthesized in rough ER → modified in Golgi → transported in vesicles → secreted or sent to lysosomes.

Endosymbiosis Hypothesis

• Mitochondria and chloroplasts originated from engulfed prokaryotes.

Cytoskeleton

• Network of fibers: microfilaments (actin), intermediate filaments, microtubules.

• Functions: Support, movement, intracellular transport.

Cellular Functions and Organelles

Motility Structures

• Motor Proteins: Move along cytoskeletal fibers.

• Centrosomes/Centrioles: Organize microtubules in animal cells.

• Basal Body: Anchors cilia/flagella.

• Dyneins: Motor proteins in cilia/flagella.

• Cilia/Flagella: Structures for cell movement; powered by microtubules and dynein.

• Microfilaments (Actin): Support cell shape, involved in movement.

• Myosin: Motor protein interacting with actin for muscle contraction.

Cell Walls and Extracellular Matrix (ECM)

• Cell Wall: Found in plants, fungi, some protists; provides support.

• ECM: Found outside animal cells; composed of glycoproteins (e.g., collagen).

Cell Junctions

• Connections between cells; types differ in plants and animals (e.g., plasmodesmata, tight junctions, desmosomes, gap junctions).

Chapter 5 – Membrane Transport & Cell Signaling

Fluid Mosaic Model

• Describes the plasma membrane as a dynamic structure with proteins floating in or on a fluid lipid bilayer.

Membrane Structure and Function

• Phospholipids: Main component; amphipathic (hydrophilic head, hydrophobic tails).

• Proteins: Integral (span membrane) and peripheral (surface-associated); serve as transporters, receptors, enzymes, anchors.

Transport Across Membranes

• Passive Transport: Movement down concentration gradient; includes diffusion and osmosis.

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

• Facilitated Diffusion: Passive transport aided by proteins (e.g., aquaporins for water).

• Active Transport: Movement against gradient; requires energy (ATP).

• Cotransport: Coupled transport of two substances; often uses a gradient established by active transport.

Bulk Transport

• Exocytosis: Secretion of materials via vesicles fusing with the membrane.

• Endocytosis: Uptake of materials via vesicle formation.

• Phagocytosis: "Cell eating"; uptake of large particles.

• Pinocytosis: "Cell drinking"; uptake of fluids.

• Receptor-Mediated Endocytosis: Specific uptake using receptor proteins.

Cell Signaling

• Signal Transduction Pathway: Series of steps by which a signal on a cell's surface is converted into a specific cellular response.

• Second Messengers: Small molecules that relay signals inside the cell (e.g., cAMP, Ca2+).

• G-Protein Coupled Receptors (GPCRs): Membrane receptors that activate G-proteins, triggering signaling cascades.

• Phosphorylation: Addition of phosphate group to proteins, often regulating activity.

• Phosphorylation Cascade: Series of protein kinases activating each other by phosphorylation.

• Testosterone Signaling: Steroid hormone passes through membrane, binds intracellular receptor, alters gene expression.

Additional info: These notes expand on the study guide prompts with academic context, definitions, and examples to provide a comprehensive review for exam preparation.