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

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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 emergent properties at each level.

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 & Organ: Body parts that perform specific functions.
Tissue: Groups of similar cells performing a function.
Cell: Smallest unit of life capable of all life functions.
Organelle: Functional components within cells.
Molecule & Atom: Chemical building blocks of all matter.

Emergent properties arise at each level due to the arrangement and interactions of parts as complexity increases.

Cells: Prokaryotic vs. Eukaryotic

Cell: The smallest unit of life.
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, Genes, and Chromosomes

DNA (Deoxyribonucleic Acid): The molecule carrying genetic instructions; 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.
Chromosome: A structure consisting of DNA and proteins, carrying genetic information.
Nucleotides: The building blocks of DNA and RNA.
Sugar-phosphate backbone: The repeating pattern of sugar and phosphate groups in DNA/RNA.
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 entering as sunlight, exiting as heat).
Nutrients cycle within ecosystems (e.g., carbon, nitrogen cycles).
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: 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:
- Bacteria: Prokaryotic, unicellular organisms.
- Archaea: Prokaryotic, often found in extreme environments.
- Eukarya: Eukaryotic organisms (plants, animals, fungi, protists).

Natural Selection

Mechanism of evolution proposed by Charles Darwin.
Individuals with advantageous traits survive and reproduce more successfully.
Explains adaptation and the connection of all life through common ancestry.

The Scientific Process

Steps: Observation, Question, Hypothesis, Prediction, Experiment, Analysis, Conclusion.
Hypothesis: A testable explanation for an observation.
Null hypothesis: A statement that there is no effect or difference.
Theory: A broad explanation supported by a large body of evidence.
Experimental group: Receives the treatment.
Control group: Does not receive the treatment; used for comparison.
Independent variable: The factor manipulated by the researcher.
Dependent variable: The factor measured in the experiment.
Blind/double-blind design: 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: A substance that cannot be broken down by chemical means.
Atom: The smallest unit of an element, composed of protons, neutrons, and electrons.
Key elements in life: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and others.

Atomic Structure and Electron Arrangement

Electrons are arranged in shells around the nucleus.
The arrangement determines chemical properties and reactivity.
Valence electrons (outermost shell) are involved in bonding.

Energy Types

Energy: The 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 bond: Unequal sharing of electrons (e.g., H2O).
Nonpolar covalent bond: Equal sharing of electrons (e.g., O2).
Hydrogen bonds: Weak bonds between a hydrogen atom and an electronegative atom.
Van der Waals interactions: Weak attractions due to transient charges.
Electronegativity: An atom's attraction for electrons in a bond.

Chemical Reactions and Equilibrium

Reactants: Starting materials in a reaction.
Products: Substances formed by a reaction.
Chemical equilibrium: When forward and reverse reactions occur at the same rate.

Properties of Water

Polarity: Water is a polar molecule due to unequal sharing of electrons.
Hydrogen bonding: Gives water unique properties (cohesion, adhesion, high specific heat).
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 its 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:

Chapter 3 – Carbon and the Molecular Diversity of Life

Organic Compounds and Carbon

Organic compounds: Molecules containing carbon and hydrogen.
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 biologically important 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 molecules made of repeating units (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; main energy source for cells.
Monosaccharides (simple sugars), disaccharides, polysaccharides (e.g., starch, cellulose).

Lipids

Hydrophobic molecules (fats, phospholipids, steroids).
Store energy, form membranes, act as hormones.

Proteins

Enzymes: Proteins that catalyze reactions.
Amino acids: Building blocks of proteins; differ by side chains (R groups).
Polypeptides: Chains of amino acids linked by peptide bonds.
Levels of protein 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.
Polynucleotides: Chains of nucleotides.
Pyrimidines: Cytosine, thymine, uracil.
Purines: Adenine, guanine.
Deoxyribose: Sugar in DNA; Ribose: Sugar in RNA.
Prime (') notation indicates carbon positions in sugars.
Double helix: Structure of DNA; two antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Structure and Microscopy

Cell: Basic unit of life; not all cells are identical.
Organelles: Specialized structures within eukaryotic cells.
Microscopes:
- 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.

Prokaryotic vs. Eukaryotic Cells

Prokaryotes: No nucleus, simple structure (e.g., bacteria).
Eukaryotes: Nucleus, complex organelles (e.g., plants, animals).
Cytoplasm: Fluid inside cells where organelles are suspended.

Cellular Structures and Organelles

Plant vs. animal cells: Plant cells have cell walls, chloroplasts, central vacuole; animal cells have lysosomes, centrioles.
Surface area to volume ratio: Limits cell size for efficient exchange of materials.
Plasma membrane: Main component is phospholipids; controls entry/exit of substances.
Endomembrane system: Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, plasma membrane.
Protein secretion: Synthesized in rough ER, modified in Golgi, transported via vesicles.
Endosymbiosis hypothesis: Mitochondria and chloroplasts originated from engulfed prokaryotes.
Cytoskeleton: Network of fibers (microfilaments, intermediate filaments, microtubules) for support and movement.
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.
Cilia/flagella: Structures for cell movement; powered by microtubules and dynein.
Microfilaments: Made of actin; involved in cell shape and movement.
Myosin: Motor protein interacting with actin.
Cell wall: Found in plants, fungi, some protists; provides support.
Extracellular matrix (ECM): Found outside animal cells; composed of proteins and carbohydrates.
Cell junctions: Connections between cells (tight junctions, desmosomes, gap junctions in animals; plasmodesmata in plants).

Chapter 5 – Membrane Transport & Cell Signaling

Membrane Structure and Function

Fluid Mosaic Model: Membrane is a fluid structure with proteins embedded in a phospholipid bilayer.
Proteins serve as channels, carriers, receptors, enzymes, anchors.

Transport Across Membranes

Selective permeability: Membrane allows some substances to cross more easily than others.
Osmosis: Diffusion of water across a membrane.
Diffusion: Movement of molecules from high to low concentration.
Passive transport: No energy required (diffusion, facilitated diffusion).
Active transport: Requires energy (ATP) to move substances against their gradient.
Aquaporin: Protein channel for water transport.
Cotransport: Coupled transport of two substances; facilitated by cotransporter proteins (often active transport).
Bulk transport: Movement of large molecules via vesicles (exocytosis, endocytosis, phagocytosis, pinocytosis, receptor-mediated endocytosis).

Cell Signaling

Cell signaling: Cells communicate via chemical signals.
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).
Testosterone signaling: Hormone binds receptor, triggers gene expression.
G-protein coupled receptors (GPCRs): Membrane receptors that activate G-proteins, initiating signaling cascades.
Phosphorylation: Addition of phosphate group to proteins, often activating them.
Phosphorylation cascade: Series of protein kinases activating each other by phosphorylation.

Table: Types of Chemical Bonds

Bond Type	Description	Example
Ionic	Transfer of electrons	NaCl
Covalent (Polar)	Unequal sharing of electrons	H2O
Covalent (Nonpolar)	Equal sharing of electrons	O2
Hydrogen	Attraction between H and electronegative atom	Between water molecules
Van der Waals	Weak, transient attractions	Gecko feet adhesion

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cell	Eukaryotic Cell
Nucleus	Absent	Present
Organelles	Few, not membrane-bound	Many, membrane-bound
Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Table: Levels of Protein Structure

Level	Description	Stabilizing Bonds
Primary	Sequence of amino acids	Peptide bonds
Secondary	Alpha helix, beta sheet	Hydrogen bonds
Tertiary	3D folding of polypeptide	Hydrogen, ionic, disulfide, hydrophobic interactions
Quaternary	Association of multiple polypeptides	Same as tertiary

Additional info: These notes synthesize foundational concepts from the first five chapters of a typical General Biology course, providing definitions, examples, and comparisons to support critical thinking and application for exam preparation.