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 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: A cell can perform life functions, but its individual molecules cannot.

Cells: Prokaryotic vs. Eukaryotic

• 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: Segment of DNA coding for a functional product (usually a protein).

• Nucleotides: Building blocks of DNA and RNA.

• Gene Expression: Process by which information from a gene is used to synthesize a functional product.

Energy Flow and Nutrient Cycling

• Energy flows through ecosystems (usually from sunlight to producers to consumers) and is lost as heat.

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

Biological Interactions

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

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

Evolution and Diversity

• Evolution: Change in genetic composition of a population over generations; explains both unity and diversity of life.

• Three Domains of Life:

  • Bacteria: Prokaryotic, diverse environments.

  • Archaea: Prokaryotic, often in extreme environments.

  • Eukarya: Eukaryotic, includes plants, animals, fungi, protists.

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: 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 not based on scientific method.

• 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; arrangement 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/molecules.

Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms.

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

• Polar Covalent: Unequal sharing due to electronegativity differences.

• Nonpolar Covalent: Equal sharing of electrons.

• Hydrogen Bonds: Weak attraction between a hydrogen atom and an electronegative atom.

• 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: Rate of forward and reverse reactions are equal.

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: Contain carbon and hydrogen; found in living things.

• Hydrocarbons: Molecules with only carbon and hydrogen.

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

• Carbon: Forms four covalent bonds; central to organic chemistry.

Chemical Groups

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

ATP (Adenosine Triphosphate)

• Organic molecule; main energy currency of the cell.

Polymers and Monomers

• Polymers: Long chains of monomers.

• Monomers: Building blocks of polymers.

• Dehydration Reaction: 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: 20 types; differ by side chains (R groups).

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

• Protein Structure: Primary, secondary, tertiary, quaternary levels.

• 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 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, 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 higher ratios for efficient exchange.

Biological Membranes

• Main Component: Phospholipids.

• Plasma Membrane: Selectively permeable boundary of the cell.

Endomembrane System

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

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

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.

Cellular Functions and Organelles

• Manufacturing: Ribosomes, ER, Golgi.

• Breakdown: Lysosomes, peroxisomes.

• Energy Processing: Mitochondria, chloroplasts.

• Support/Movement/Communication: Cytoskeleton, plasma membrane, cell wall, ECM.

Motor Proteins and Structures

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

• Centrosomes/Centrioles: Organize microtubules in animal cells.

• Basal Body: Anchors cilia/flagella.

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

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

Cell Walls and ECM

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

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

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 dynamic structure with proteins floating in or on a fluid lipid bilayer.

Membrane Structure and Function

• Phospholipids: Form bilayer; hydrophilic heads, hydrophobic tails.

• Proteins: Integral (span membrane) and peripheral (surface); functions include transport, signaling, cell recognition.

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 aided by proteins (e.g., aquaporins for water).

• Active Transport: Requires energy (ATP); moves substances against concentration gradient.

• Cotransport: Coupled transport of two substances; one moves down gradient, driving the other up.

Bulk Transport

• Exocytosis: Secretion of materials out of the cell via vesicles.

• Endocytosis: Uptake of materials into the cell.

• Phagocytosis: "Cell eating"; engulfing large particles.

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

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

Selective Permeability

• Membrane allows some substances to cross more easily than others; facilitated by proteins and lipid composition.

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 (e.g., cAMP) that relay signals inside the cell.

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

• Phosphorylation: Addition of phosphate group to proteins, often activating them.

• 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 alters gene expression.

Additional info: This guide covers foundational concepts from the first five chapters of a General Biology course, including cell structure, chemistry, macromolecules, and membrane dynamics. Students should integrate these concepts for critical thinking and application on exams.