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

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.

• Organelle: Functional components within cells.

• Molecule: Chemical structure 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 isolated chlorophyll molecules.

Cells: Prokaryotic vs. Eukaryotic

• Cell: The smallest unit of life capable of performing all life functions.

• 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 molecule composed of nucleotides (adenine, thymine, cytosine, guanine) with a sugar-phosphate backbone.

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

• Nucleotides: Building blocks of DNA and RNA, 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, being reused and recycled among organisms and the environment.

Biological Interactions

• Producers (Autotrophs): Organisms that produce their own food (e.g., plants via photosynthesis).

• Consumers (Heterotrophs): Organisms that consume other organisms for energy.

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 (adaptations) of life.

Three Domains of Life

Domain	Characteristics	Examples
Bacteria	Prokaryotic, unicellular	Escherichia coli
Archaea	Prokaryotic, often extremophiles	Halobacterium
Eukarya	Eukaryotic, unicellular or multicellular	Plants, animals, fungi, protists

Natural Selection

• Mechanism of evolution proposed by Charles Darwin.

• Individuals with advantageous traits survive and reproduce, passing traits to offspring.

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.

• 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 evidence.

• 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; their distribution determines chemical properties.

• 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 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; 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 (polar).

• Hydrophobic: Water-fearing substances (nonpolar).

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.

• 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

• Polymer: Long molecule made of repeating units (monomers).

• Monomer: Building block of a polymer.

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

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

• Include sugars and starches; serve as energy sources and structural materials.

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

Lipids

• Hydrophobic molecules including fats, phospholipids, steroids.

• Store energy, form membranes, act as hormones.

Proteins

• Composed of amino acids linked by peptide bonds.

• Serve as enzymes, structural components, transporters, etc.

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

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

Nucleic Acids

• DNA and RNA; store and transmit genetic information.

• Composed of nucleotides (sugar, phosphate, nitrogenous base).

• Pyrimidines: Cytosine, Thymine, Uracil.

• Purines: Adenine, Guanine.

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

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

Chapter 4 – A Tour of the Cell

Cell Structure and Function

• Cells are the basic units of life; not all cells are the same.

• Organelles: Specialized structures within eukaryotic cells.

Microscopy

• Light Microscope: Uses light to view cells.

• Electron Microscope: Uses electrons for higher resolution.

• Scanning Electron Microscope (SEM): Views cell surfaces in detail.

Cell Fractionation

• Technique to separate cell components for study.

Prokaryotic vs. Eukaryotic Cells

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

• Eukaryotes: Nucleus, complex organelles (e.g., plants, animals).

Cellular Structures

• Cytoplasm: Fluid inside cells where organelles are suspended.

• 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 higher ratios for efficient exchange.

Biological Membranes

• Main Component: Phospholipids form the plasma membrane.

• Plasma Membrane: Selectively permeable barrier around cells.

Endomembrane System

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

• Involved in protein synthesis, modification, transport, and breakdown.

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, intermediate filaments, microtubules) for support, movement, and transport.

• Motor Proteins: Move along cytoskeleton to transport materials.

• Centrosomes/Centrioles: Organize microtubules in animal cells.

• Basal Body: Anchors cilia/flagella.

• Dyneins: Motor proteins in cilia/flagella.

• Actin/Myosin: Proteins involved in muscle contraction and cell movement.

Cell Walls and Extracellular Matrix (ECM)

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

• ECM: Network outside animal cells; composed of proteins and carbohydrates.

Cell Junctions

• Structures that connect cells and facilitate communication (e.g., plasmodesmata in plants, gap junctions in animals).

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

• Composed of phospholipids, proteins, cholesterol, and carbohydrates.

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

Transport Mechanisms

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

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

• Passive Transport: No energy required (diffusion, facilitated diffusion).

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

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

• Aquaporin: Protein channel that facilitates water movement.

Cotransport and Bulk Transport

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

• Bulk Transport: Movement of large particles via vesicles (exocytosis, endocytosis).

• Exocytosis: Vesicles fuse with membrane to release contents.

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

Cell Signaling

• Cells communicate via chemical signals; the plasma membrane plays a key role in receiving and transmitting signals.

• 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).

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

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

• Phosphorylation Cascade: Series of protein kinases activating each other by phosphorylation, amplifying the signal.

Example: Testosterone Signaling

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

Additional info: Some explanations and examples were expanded for clarity and completeness, as the original file was a question-based review guide.