General Biology Exam 1 Study Guide: Foundations, Chemistry, Cells, and Membranes

Chapter 1 – Evolution and the Foundations of Biology

Hierarchy of Life

• Biosphere: The largest level, encompassing all ecosystems on Earth.

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

• Community: All organisms in an ecosystem.

• Population: Individuals of the same species in a given area.

• Organism: An individual living entity.

• Organ System & Organ: Groups of tissues working together for specific functions.

• Tissue: Groups of similar cells performing a function.

• Cell: The smallest unit of life.

• Organelle: Functional components within cells.

• Molecule & Atom: Chemical building blocks of all matter.

Emergent Properties

• New properties arise at each level in the biological hierarchy due to the arrangement and interactions of parts.

• Example: A functioning organ system emerges from the coordinated activity of organs.

Cells: Prokaryotic vs. Eukaryotic

• Smallest unit of life: The cell.

• 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 Gene Expression

• DNA (Deoxyribonucleic Acid): Double helix 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.

• Nucleotides: Building blocks of DNA, each consisting of a sugar, phosphate group, and nitrogenous base.

• 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 from sunlight to producers to consumers) and is eventually lost as heat.

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

Biological Interactions

• Producers (Autotrophs): Organisms (like plants) that produce organic molecules from inorganic sources using energy (usually sunlight).

• Consumers (Heterotrophs): Organisms that obtain energy by consuming other organisms.

Evolution and Diversity

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

• Accounts for both the unity (shared traits) and diversity (differences) of organisms.

Three Domains of Life

Domain	Characteristics
Bacteria	Prokaryotic, diverse, found in many environments
Archaea	Prokaryotic, often in extreme environments
Eukarya	Eukaryotic, includes plants, animals, fungi, protists

Natural Selection

• Mechanism of evolution proposed by Charles Darwin.

• Organisms 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: Standard for comparison.

• Blind/Double Blind: Reduces bias in experiments.

• Pseudoscience: Claims lacking scientific evidence.

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

Inductive vs. Deductive Reasoning

• Inductive: Specific observations to general conclusions.

• Deductive: General premises to specific predictions.

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/molecules.

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 differences in electronegativity (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 covalent 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 of 1g by 1°C.

• 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, dissolves in water.

• Hydrophobic: Water-fearing, does 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: Contain carbon and hydrogen, often with other elements.

• Hydrocarbons: Molecules with only carbon and hydrogen.

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

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

Chemical Groups

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

ATP (Adenosine Triphosphate)

• Organic molecule that stores and transfers energy in cells.

Polymers and Monomers

• Polymers: Long chains of monomers.

• Monomers: Building blocks of polymers.

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

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

• Include sugars and starches.

• Monosaccharides (simple sugars), disaccharides, polysaccharides (complex carbs).

• Function: Energy storage, structural support.

Lipids

• Fats, phospholipids, steroids.

• Hydrophobic, energy storage, membrane structure, signaling.

Proteins

• Composed of amino acids linked by peptide bonds.

• Levels of structure: Primary, secondary, tertiary, quaternary.

• Function: Enzymes, structure, transport, signaling.

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

Nucleic Acids

• DNA and RNA; polymers of nucleotides.

• Pyrimidines: Cytosine, Thymine, Uracil.

• Purines: Adenine, Guanine.

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

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

• Prime (') notation indicates carbon positions in sugar rings.

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 Microscope: Uses light to view cells; limited resolution.

• Electron Microscope: Uses electrons for higher resolution.

• Scanning Electron Microscope (SEM): Surface details.

• Transmission Electron Microscope (TEM): Internal structures.

Cell Fractionation

• Technique to separate cell components for study.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, simple structure (bacteria, archaea).

• Eukaryotes: Nucleus, complex organelles (plants, animals, fungi, protists).

Cellular Structures

• Cytoplasm: Fluid inside the cell, contains organelles.

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

• Surface Area to Volume Ratio: Limits cell size; smaller cells have more efficient exchange with environment.

Biological Membranes

• Main lipid: Phospholipids.

• 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 become lysosomes.

Endosymbiosis Hypothesis

• Mitochondria and chloroplasts originated as free-living prokaryotes engulfed by ancestral eukaryotes.

Cytoskeleton

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

• Functions: Support, movement, cell division.

Motor Proteins and Cellular Movement

• Motor Proteins: Move along cytoskeleton (e.g., dyneins, myosin).

• Centrosomes/Centrioles: Organize microtubules in animal cells.

• Basal Body: Anchors cilia/flagella.

• Cilia/Flagella: Structures for movement; powered by dynein arms sliding microtubules.

Cell Walls and Extracellular Matrix (ECM)

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

• ECM: Found outside animal cells; composed of glycoproteins, supports and anchors cells.

Cell Junctions

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

Chapter 5 – Membrane Transport & Cell Signaling

Fluid Mosaic Model

• Describes the plasma membrane as a flexible layer with proteins embedded in or attached to a phospholipid bilayer.

Membrane Structure and Function

• Composed of phospholipids, proteins, cholesterol, carbohydrates.

• Proteins serve as channels, carriers, receptors, enzymes, anchors.

Transport Across Membranes

• Passive Transport: No energy required; includes diffusion and osmosis.

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

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

• Facilitated Diffusion: Passive transport via proteins.

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

• Selective Permeability: Membrane allows some substances to pass more easily than others.

• Aquaporins: Channel proteins for water transport.

Cotransport and Bulk Transport

• Cotransport: Coupled transport of two substances via a protein; often uses energy from one gradient to move another molecule.

• Bulk Transport: Movement of large particles via vesicles.

• Exocytosis: Vesicles fuse with membrane to release contents outside cell.

• Endocytosis: Cell takes in materials via vesicles (includes phagocytosis, pinocytosis, receptor-mediated endocytosis).

Cell Signaling

• Cells communicate via chemical signals; involves reception, transduction, and response.

• Signal Transduction Pathway: Series of steps converting a signal to a cellular response.

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

• 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.

Example: Testosterone Signaling

• Testosterone (a steroid hormone) passes through the membrane, binds to intracellular receptor, and activates gene expression.

Additional info: This guide covers foundational concepts for General Biology, including cell structure, chemistry, macromolecules, and membrane dynamics, with emphasis on critical thinking and application.