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, providing a framework for understanding complexity in living systems.

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

• Ecosystem: Communities of organisms interacting with their physical environment.

• Community: All organisms living in a particular area.

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

• Organism: An individual living entity.

• Organ/Organ System: Structures with specific functions.

• Tissue: Groups of cells with a common function.

• Cell: The smallest unit of life.

• Organelle: Specialized structures within cells.

• Molecule: Groups of atoms bonded together.

• Atom: Smallest unit of matter.

Emergent Properties

Emergent properties arise when components interact, producing characteristics not found in individual parts.

• Definition: New properties that emerge at each level of organization due to interactions among parts.

• Example: A cell is alive, but its individual molecules are not.

Cell Types: Eukaryotic vs. Prokaryotic

Cells are the fundamental units of life, classified as eukaryotic or prokaryotic based on structural differences.

• Eukaryotic Cells: Contain membrane-bound organelles, including a nucleus.

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

DNA Structure and Function

DNA is the hereditary material, composed of nucleotides and organized into chromosomes.

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

• Sugar-Phosphate Backbone: The structural framework of DNA.

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

• Chromosome: DNA packaged with proteins.

• 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 functional products.

• Transcription: DNA is copied into RNA.

• Translation: RNA is used to build proteins.

Energy Flow and Nutrient Cycling

Energy flows through ecosystems, while nutrients cycle within them.

• Energy Flow: Sunlight → Producers → Consumers → Decomposers.

• Nutrient Cycling: Elements like carbon and nitrogen are recycled by organisms.

Biological Interactions: Producers and Consumers

• Producers: Autotrophs (e.g., plants) that convert energy from sunlight.

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

Evolution and Unity/Diversity of Life

Evolution explains both the unity and diversity of life.

• Definition: Change in genetic composition of populations over time.

• Unity: Shared traits due to common ancestry.

• Diversity: Adaptations to different environments.

Three Domains of Life

Life is classified into three domains based on cellular characteristics.

Domain	Characteristics	Examples
Bacteria	Prokaryotic, diverse, found everywhere	Escherichia coli
Archaea	Prokaryotic, often extremophiles	Halobacterium
Eukarya	Eukaryotic, includes plants, animals, fungi, protists	Homo sapiens, Zea mays

Natural Selection

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

• Definition: Differential survival and reproduction of individuals due to variation.

• Connection: All life is related through evolutionary history.

Scientific Process

The scientific method is a systematic approach to inquiry.

• Steps: Observation → Question → Hypothesis → Experiment → 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.

• Independent Variable: Manipulated factor.

• Dependent Variable: Measured outcome.

• Blind/Double Blind: Reduces bias.

• Statistics: Importance of sample size and variable relationships.

• Pseudoscience: Claims lacking scientific basis.

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

Chapter 2 – The Chemical Context of Life

Key Elements in Living Organisms

Living organisms are primarily composed of a few key elements.

• Major Elements: Carbon, Hydrogen, Oxygen, Nitrogen.

• Trace Elements: Required in small amounts (e.g., Iron, Iodine).

Atoms and Their Parts

An atom consists of protons, neutrons, and electrons.

• Protons: Positive charge, found in nucleus.

• Neutrons: No charge, found in nucleus.

• Electrons: Negative charge, orbit nucleus.

Electron Arrangement and Chemical Properties

Electron configuration determines an atom's chemical behavior.

• Electron Shells: Energy levels where electrons reside.

• Valence Electrons: Electrons in the outermost 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 movement of atoms/molecules.

Types of Chemical Bonds

Atoms form bonds to achieve stable electron configurations.

• Ionic Bonds: Transfer of electrons; forms ions.

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

• Polar Covalent: Unequal sharing; creates partial charges.

• Nonpolar Covalent: Equal sharing.

• Hydrogen Bonds: Attraction between partial charges (e.g., in water).

• Van der Waals: Weak attractions between molecules.

Electronegativity

Electronegativity is an atom's ability to attract electrons.

• High Electronegativity: Atoms like oxygen and nitrogen.

• Determines: Whether bonds are polar or nonpolar.

Chemical Reactions and Equilibrium

• Reactants: Starting materials.

• Products: Resulting substances.

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

Properties of Water

Water's unique properties are due to its polarity and hydrogen bonding.

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

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

• Evaporative Cooling: As water evaporates, it cools surfaces.

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

• Solvent of Life: Water dissolves many substances.

• Hydrophilic: Water-loving; polar molecules.

• Hydrophobic: Water-fearing; nonpolar molecules.

Acids, Bases, and pH

• Acid: Increases H+ concentration.

• Base: Increases OH- concentration.

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

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

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 (e.g., proteins, nucleic acids).

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

Chemical Groups Attached to Carbon Skeletons

Functional groups determine the properties of organic molecules.

Group	Structure	Function
Hydroxyl	-OH	Alcohols; polar
Carbonyl	>C=O	Ketones, aldehydes
Carboxyl	-COOH	Acids
Amino	-NH2	Bases
Sulfhydryl	-SH	Thiols
Phosphate	-PO4	Energy transfer
Methyl	-CH3	Gene expression

ATP: Structure and Function

• ATP (Adenosine Triphosphate): Organic molecule; main energy carrier in cells.

• Function: Transfers energy for cellular processes.

Macromolecules: Polymers and Monomers

• Polymers: Long chains of monomers.

• Monomers: Building blocks (e.g., amino acids, nucleotides).

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

• Hydrolysis: Breaks polymers by adding water.

Carbohydrates

• Structure: (CH2O)n; monosaccharides, disaccharides, polysaccharides.

• Function: Energy storage, structural support.

• Example: Glucose, starch, cellulose.

Lipids

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

• Function: Energy storage, membrane structure, signaling.

• Example: Triglycerides, cholesterol.

Proteins

• Enzymes: Proteins that catalyze reactions.

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

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

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

• Denaturation: Loss of structure due to environmental changes.

Nucleic Acids

• Types: DNA and RNA.

• Polynucleotides: Chains of nucleotides.

• Pyrimidines: Cytosine, thymine, uracil.

• Purines: Adenine, guanine.

• Deoxyribose: Sugar in DNA.

• Ribose: Sugar in RNA.

• Prime (’): Denotes carbon positions in sugars.

• Double Helix: Structure of DNA; antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Structure and Function

Cells are the basic units of life, with specialized structures called organelles.

• Microscopes: Light (general view), electron (detailed structure), scanning electron (surface details).

• Cell Fractionation: Separates cell components for study.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: No nucleus, simple structure, found in Bacteria and Archaea.

• Eukaryotes: Nucleus, complex organelles, found in Eukarya.

Cellular Structures in Prokaryotes

• Cytoplasm: Fluid inside cell.

• Cell Wall: Provides structure.

• Plasma Membrane: Controls entry/exit.

Cellular Structures/Organelles in Eukaryotes

• Nucleus: Contains DNA.

• Endoplasmic Reticulum: Protein and lipid synthesis.

• Golgi Apparatus: Modifies, packages proteins.

• Mitochondria: Energy production.

• Chloroplasts: Photosynthesis (plants).

• Lysosomes: Breakdown of materials.

• Vacuoles: Storage.

Animal vs. Plant Cells

• Plant Cells: Cell wall, chloroplasts, large central vacuole.

• Animal Cells: No cell wall, no chloroplasts, small vacuoles.

Surface Area to Volume Ratio

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

• Formula: $\text{Surface Area} = 6a^2$, $\text{Volume} = a^3$ for a cube.

Biological Membranes

• Main Component: Phospholipids.

• Plasma Membrane: Boundary of cell.

Endomembrane System

• Includes: Nuclear envelope, ER, Golgi, 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

• Microtubules: Tubulin; support, movement.

• Microfilaments: Actin; movement, shape.

• Intermediate Filaments: Structural support.

Motor Proteins and Cellular Movement

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

• Centrosomes/Centrioles: Organize microtubules.

• Basal Body: Anchors cilia/flagella.

• Cilia/Flagella: Movement; powered by dyneins.

Cell Wall and Extracellular Matrix (ECM)

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

• ECM: Found outside animal cells; composed of proteins (collagen, proteoglycans).

Cellular Surface and Junctions

• Plant Cells: Plasmodesmata (channels).

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

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.

• Proteins: Embedded; serve various functions.

Membrane Structure and Associated Proteins

• Integral Proteins: Span membrane.

• Peripheral Proteins: Attached to surface.

• Functions: Transport, signaling, cell recognition.

Membrane Transport Mechanisms

• Diffusion: Movement from high to low concentration.

• Osmosis: Diffusion of water.

• Passive Transport: No energy required.

• Active Transport: Requires ATP; moves against gradient.

• Selective Permeability: Only certain molecules pass.

• Aquaporins: Channel proteins for water.

Cotransport and Bulk Transport

• Cotransport: Coupled transport of two substances; facilitated by protein.

• Bulk Transport: Exocytosis (out), endocytosis (in), phagocytosis (cell eating), pinocytosis (cell drinking), receptor-mediated endocytosis.

Cell Signaling and Signal Transduction

• Cell Signaling: Communication via chemical signals.

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

• Second Messengers: Small molecules relaying signals (e.g., cAMP).

• Testosterone: Hormone; triggers transduction pathway for gene expression.

G-Protein Coupled Receptors (GPCRs)

• Location: Plasma membrane.

• Function: Activate G-proteins, which trigger downstream effects.

Phosphorylation and Protein Kinases

• Phosphorylation: Addition of phosphate group to protein.

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

Additional info: Where original content was brief, academic context and examples were added for completeness and clarity.