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

Chapter 1 – Evolution and the Foundations of Biology

Hierarchy of Life and Emergent Properties

The hierarchy of life describes the organization of biological systems from the largest to the smallest scale, each level exhibiting emergent properties not present in the preceding level.

• Biosphere: The global ecological system integrating all living beings and their relationships.

• Emergent Properties: New characteristics that arise at each level of organization due to the arrangement and interaction of parts. For example, a cell exhibits properties not found in its individual molecules.

• Smallest Unit of Life: The cell is the fundamental unit of life.

Cell Types: Eukaryotic vs Prokaryotic

Cells are classified as either prokaryotic or eukaryotic based on structural differences.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; DNA is found in the nucleoid region.

• Eukaryotic Cells: Possess a nucleus and various membrane-bound organelles.

DNA Structure and Function

DNA is the hereditary material in cells, composed of nucleotides forming a double helix.

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

• Sugar-Phosphate Backbone: The structural framework of DNA formed by alternating sugars and phosphates.

• Gene: A segment of DNA encoding a functional product, usually a protein.

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

• Job of DNA: Stores genetic information and directs gene expression.

Gene Expression

Gene expression is the process by which information from a gene is used to synthesize a functional product.

• Transcription: DNA is copied into RNA.

• Translation: RNA is used to build proteins.

Energy Flow and Nutrient Cycling

Energy flows through ecosystems, while nutrients are recycled.

• Producers: Organisms (e.g., plants) that convert solar energy into chemical energy.

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

• Energy Flow: Energy enters as sunlight, is converted by producers, and flows to consumers; it is lost as heat.

• Nutrient Cycling: Nutrients are recycled through biotic and abiotic components.

Evolution and Diversity

Evolution explains both the unity and diversity of life.

• Evolution: Change in the genetic composition of populations over time.

• Unity: Shared characteristics due to common ancestry.

• Diversity: Variations due to adaptation and speciation.

Three Domains of Life

Life is classified into three domains based on cellular characteristics.

Domain	Characteristics	Examples
Bacteria	Prokaryotic, diverse metabolic types	Escherichia coli
Archaea	Prokaryotic, often extremophiles	Halobacterium
Eukarya	Eukaryotic, includes plants, animals, fungi, protists	Homo sapiens, Arabidopsis thaliana

Natural Selection

Natural selection is the mechanism of evolution proposed by Charles Darwin.

• Natural Selection: Differential survival and reproduction of individuals due to differences in phenotype.

• Charles Darwin: Credited with the theory of natural selection.

Scientific Process

The scientific method is a systematic approach to inquiry.

• Steps: Observation, Question, Hypothesis, Experiment, Data Collection, Analysis, Conclusion.

• Hypothesis: Testable explanation.

• Null Hypothesis: No effect or relationship.

• Theory: Broad explanation supported by evidence.

• Experimental Group: Receives treatment.

• Control Group: No treatment; baseline.

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

• Blind/Double Blind: Reduces bias.

• Statistics: Importance of sample size and variable relationships.

• Pseudoscience: Claims lacking scientific evidence.

• Anecdotal Evidence: Based on personal accounts, not scientific data.

Inductive vs Deductive Reasoning

Reasoning methods used in science.

• Inductive Reasoning: Generalizations from specific observations.

• Deductive Reasoning: Predictions from general principles.

Chapter 2 – The Chemical Context of Life

Elements and Atoms

Elements are pure substances consisting of one type of atom, which is composed of protons, neutrons, and electrons.

• Key Elements: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur.

• Atom Structure: Protons (+), Neutrons (0), Electrons (-).

Electron Arrangement and Chemical Properties

Electron configuration determines an atom's chemical properties.

• Electron Shells: Energy levels where electrons reside.

• Valence Electrons: Electrons in the outer shell; determine reactivity.

Types of Energy

• Energy: Capacity to do work.

• Potential Energy: Stored energy due to position.

• Kinetic Energy: Energy of motion.

• Thermal Energy: Energy from random molecular movement.

Chemical Bonds

Atoms form bonds to achieve stable electron configurations.

• Ionic Bonds: Transfer of electrons.

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

• Hydrogen Bonds: Attraction between hydrogen and electronegative atom.

• Van der Waals Interactions: Weak attractions between molecules.

Electronegativity and Bond Polarity

• Electronegativity: Atom's ability to attract electrons.

• Polar Covalent Bonds: Unequal sharing; molecule is hydrophilic.

• Nonpolar Covalent Bonds: Equal sharing; molecule is hydrophobic.

Chemical Reactions and Equilibrium

• Reactants: Starting materials.

• Products: Resulting substances.

• Chemical Equilibrium: Rate of forward and reverse reactions are equal.

Properties of Water

Water is a polar molecule with unique properties essential for life.

• Polarity: Oxygen is more electronegative, creating partial charges.

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

• Evaporative Cooling: Loss of heat as water evaporates.

• Ice Floats: Due to lower density; important for aquatic life.

• Solvent of Life: Water dissolves many substances.

• Hydrophilic: Water-loving; polar.

• Hydrophobic: Water-fearing; nonpolar.

Acids, Bases, and pH

• Acid: Increases H+ concentration.

• Base: Increases OH- concentration.

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

• pH Equation:

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

Chapter 3 – Carbon and Molecular Diversity of Life

Organic Compounds and Hydrocarbons

Organic compounds contain carbon; hydrocarbons are composed only of carbon and hydrogen.

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

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

Chemical Groups and ATP

• Chemical Groups: Functional groups attached to carbon skeletons; seven important groups include hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl.

• ATP: Adenosine triphosphate; 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

• Structure: Composed of monosaccharides (e.g., glucose).

• Function: Energy storage and structural support.

Lipids

• Structure: Mostly hydrophobic; includes fats, phospholipids, steroids.

• Function: Energy storage, membrane structure, signaling.

Proteins and Amino Acids

• Enzymes: Protein catalysts.

• Amino Acids: Differ by side chains (R groups).

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

• Protein Structure: Four levels: primary, secondary, tertiary, quaternary.

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

Nucleic Acids

• Types: DNA and RNA.

• Polynucleotides: Long chains of nucleotides.

• Pyrimidines: Cytosine, Thymine, Uracil.

• Purines: Adenine, Guanine.

• Deoxyribose: Sugar in DNA.

• Ribose: Sugar in RNA.

• Prime (’): Denotes carbon positions in sugar ring.

• Double Helix: Structure of DNA; antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Structure and Microscopy

Cells are the basic units of life; microscopy is essential for studying them.

• Light Microscope: Uses visible light; good for living cells.

• Electron Microscope: Uses electron beams; higher resolution.

• Scanning Electron Microscope: Surface details.

• Cell Fractionation: Separates cell components.

Prokaryotic vs Eukaryotic Cells

• Prokaryotes: No nucleus; simple structure.

• Eukaryotes: Nucleus; complex organelles.

Cellular Structures and Organelles

• Cytoplasm: Fluid inside cells.

• Organelles: Specialized structures (e.g., mitochondria, chloroplasts).

• Animal vs Plant Cells: Plant cells have cell walls, chloroplasts; animal cells have lysosomes, centrioles.

Surface Area to Volume Ratio

Cells are small to maximize surface area for exchange relative to volume.

• Formula:

$\text{Surface Area} \propto r^2$ $\text{Volume} \propto r^3$

Biological Membranes

• Main Lipid: Phospholipids.

• Plasma Membrane: Boundary of the cell.

Endomembrane System

• Components: Nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, plasma membrane.

• Protein Secretion: Synthesized in ER, modified in Golgi, transported via vesicles.

Endosymbiosis Hypothesis

Explains origin of mitochondria and chloroplasts as formerly free-living prokaryotes.

Cytoskeleton and Cell Movement

• Types of Fibers: Microtubules, microfilaments, intermediate filaments.

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

• Centrosomes/Centrioles: Organize microtubules.

• Basal Body: Anchors cilia/flagella.

• Cilia/Flagella: Movement structures; powered by dyneins.

• Microfilaments: Actin filaments; interact with myosin for movement.

Cell Wall and Extracellular Matrix

• Cell Wall: Found in plants, fungi, bacteria.

• Extracellular Matrix (ECM): Found outside animal cells; composed of proteins and carbohydrates.

Cell Junctions

• Animal Cells: Tight junctions, desmosomes, gap junctions.

• Plant Cells: Plasmodesmata.

Chapter 5 – Membrane Transport & Cell Signaling

Fluid Mosaic Model

The plasma membrane is a dynamic structure composed of lipids and proteins.

• Phospholipid Bilayer: Provides fluidity and selective permeability.

• Proteins: Integral and peripheral; serve transport, signaling, structural roles.

Membrane Transport

• Osmosis: Diffusion of water.

• Diffusion: Movement from high to low concentration.

• Passive Transport: No energy required.

• Active Transport: Requires ATP; moves against gradient.

• Selective Permeability: Only certain molecules pass.

• Aquaporin: Protein channel for water.

Cotransport and Bulk Transport

• Cotransport: Coupled transport of two substances; facilitated by cotransporter proteins; usually active transport.

• Bulk Transport: Movement of large molecules.

• Exocytosis: Release of substances.

• Endocytosis: Uptake of substances.

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

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

• Receptor-Mediated Endocytosis: Specific uptake via receptors.

Cell Signaling and Signal Transduction

• Cell Signaling: Communication between cells via chemical signals.

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

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

• Testosterone Signaling: Hormone binds receptor, triggers transduction pathway, alters gene expression.

G-Protein Coupled Receptors (GPCRs)

• GPCRs: Membrane proteins that activate G-proteins upon ligand binding.

• Location: Plasma membrane.

• Activation: Ligand binding activates G-protein, which triggers downstream effects.

Phosphorylation and Cascades

• Phosphorylation: Addition of phosphate group to proteins.

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

Example: In cell signaling, a ligand binds to a receptor, activating a phosphorylation cascade that ultimately changes gene expression or cellular activity.

Additional info: Where original notes were brief, academic context and definitions were added for clarity and completeness.