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

Chapter 1 – Evolution and the Foundations of Biology

Hierarchy of Life

The biological world is organized into a hierarchy from the largest to the smallest levels, each with unique properties and functions.

• Biosphere: All life on Earth and the places where life exists.

• Ecosystem: All living things in a particular area, along with nonliving components.

• Community: All organisms in an ecosystem.

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

• Organism: An individual living thing.

• Organ/Organ System: Body parts that perform specific functions.

• Tissue: Groups of similar cells performing a function.

• Cell: The smallest unit of life.

• Organelle: Functional components within cells.

• Molecule: Chemical structure of two or more atoms.

• Atom: Smallest unit of matter.

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

Cells: The Basic Unit of Life

• 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): The molecule that stores genetic information. Composed of nucleotides (adenine, thymine, cytosine, guanine) with a sugar-phosphate backbone.

• Chromosome: DNA packaged with proteins.

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

• 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, typically entering as sunlight and exiting as heat.

• Nutrients cycle within ecosystems, being reused by producers, consumers, and decomposers.

• Producers (e.g., plants): Convert solar energy to chemical energy.

• Consumers: Obtain energy by eating other organisms.

Evolution and Diversity of Life

• Evolution: The process of change that has transformed life on Earth; explains both unity and diversity of life.

• Three Domains of Life:

  • Bacteria: Prokaryotic, diverse environments.

  • Archaea: Prokaryotic, often 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.

The Scientific Process

• Scientific Method Steps:

  1. Observation

  2. Question

  3. Hypothesis (and null hypothesis)

  4. Prediction

  5. Experiment

  6. Analysis

  7. Conclusion

• Inductive reasoning: Deriving generalizations from specific observations.

• Deductive reasoning: Making predictions based on general premises.

• Theory: Broader than a hypothesis; supported by a large body of evidence.

• Variables:

  • Independent variable: Manipulated factor.

  • Dependent variable: Measured outcome.

• Control group: Standard for comparison.

• Experimental group: Receives the treatment.

• Blind/double-blind design: Reduces bias.

• 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.

• Proton: Positive charge; Neutron: No charge; Electron: Negative charge.

Electron Arrangement and Chemical Properties

• Electrons are arranged in shells around the nucleus.

• The chemical properties of an atom depend on the number and arrangement of electrons, especially in the outermost shell (valence shell).

• Electron distribution determines how atoms interact and bond.

Types of Chemical Bonds

• Ionic bonds: Transfer of electrons between atoms.

• Covalent bonds: Sharing of electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

• Hydrogen bonds: Weak attractions between polar molecules.

• Van der Waals interactions: Weak, transient attractions between molecules.

• Electronegativity: Atom's ability to attract electrons; differences lead to polar or nonpolar bonds.

Chemical Reactions and Equilibrium

• Chemical reaction: Making and breaking of chemical bonds.

• Reactants: Starting materials; Products: Resulting substances.

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

Properties of Water

• Polarity: Water is a polar molecule due to unequal sharing of electrons.

• Hydrogen bonding gives water unique properties:

  • Cohesion and adhesion

  • High specific heat: Resists temperature change

  • Evaporative cooling: Removes heat as water evaporates

  • Ice floats: Solid water is less dense than liquid

  • Solvent of life: Dissolves many substances

• Hydrophilic: Water-loving; Hydrophobic: Water-fearing

Acids, Bases, and pH

• Acid: Increases H+ concentration; Base: Reduces H+ or increases OH-.

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

• $\text{pH} = -\log_{10}[H^+]$

Chapter 3 – Carbon and the Molecular Diversity of Life

Organic Compounds and Carbon

• Organic compounds: Contain carbon and hydrogen.

• Hydrocarbons: Molecules of only carbon and hydrogen.

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

• Carbon forms four covalent bonds, allowing for diverse structures.

Chemical Groups and ATP

• Seven important chemical groups: hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl.

• ATP (Adenosine triphosphate): Main energy currency of the cell.

Macromolecules: Polymers and Monomers

• Polymers: Long chains of monomers.

• Monomers: Building blocks of polymers.

• Dehydration (condensation) reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Carbohydrates

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

• Functions: Energy storage, structural support.

Lipids

• Fats (triglycerides), phospholipids, steroids.

• Functions: 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:

  1. Primary: Amino acid sequence

  2. Secondary: Alpha helices and beta sheets

  3. Tertiary: 3D folding

  4. Quaternary: Multiple polypeptides

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

• Enzymes: Protein catalysts that speed up reactions.

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 ring.

• Double helix: DNA's two antiparallel strands.

Chapter 4 – A Tour of the Cell

Cell Types and Organelles

• Prokaryotic cells: No nucleus, simple structure (bacteria, archaea).

• Eukaryotic cells: Nucleus, complex organelles (plants, animals, fungi, protists).

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

• Cytoplasm: Fluid inside the cell.

Microscopy and Cell Fractionation

• Light microscope: Uses light to view cells.

• Electron microscope: Higher resolution; Scanning electron microscope (SEM): Surface details.

• Cell fractionation: Separates cell components for study.

Cellular Structures and Functions

• 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; higher ratio allows efficient exchange.

• Plasma membrane: Phospholipid bilayer; controls entry/exit.

• Endomembrane system: Includes ER, Golgi apparatus, lysosomes, vesicles.

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

• Endosymbiosis hypothesis: Mitochondria and chloroplasts originated from engulfed prokaryotes.

Cytoskeleton and Cell Movement

• Cytoskeleton: Network of fibers (microtubules, microfilaments, intermediate filaments) for support and movement.

• Motor proteins: Move vesicles and organelles along cytoskeleton.

• Centrosomes: Organize microtubules; Centrioles: Found in animal cells.

• Cilia and flagella: Motile structures; movement via dynein motor proteins.

• Microfilaments: Made of actin; interact with myosin for muscle contraction.

Cell Walls, ECM, and Junctions

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

• Extracellular matrix (ECM): Outside animal cells; composed of glycoproteins (e.g., collagen).

• Cell junctions: Plasmodesmata (plants), tight junctions, desmosomes, gap junctions (animals).

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.

• Selective permeability: Only certain molecules cross easily.

• Aquaporins: Channel proteins for water transport.

Transport Mechanisms

• Passive transport: No energy required; includes diffusion and osmosis.

• Active transport: Requires ATP; moves substances against concentration gradient.

• Cotransport: Coupled transport of two substances; uses a protein (symporter or antiporter).

• Bulk transport: Movement of large molecules via vesicles (exocytosis, endocytosis, phagocytosis, pinocytosis, receptor-mediated endocytosis).

Cell Signaling

• Signal transduction pathway: Series of steps by which a signal on a cell's surface is converted to a specific 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; phosphorylation cascade amplifies signals via protein kinases.

• Testosterone signaling: Hormone binds receptor, triggers gene expression changes.

Transport Type	Energy Required?	Direction (relative to gradient)	Example
Passive (Diffusion/Osmosis)	No	Down	O2 diffusion
Active Transport	Yes (ATP)	Up	Na+/K+ pump
Cotransport	Indirect (uses gradient)	Up/Down	Glucose/Na+ symport
Bulk Transport	Yes (vesicles)	Varies	Phagocytosis

Example: The sodium-potassium pump uses ATP to move Na+ out of and K+ into the cell, maintaining electrochemical gradients essential for nerve function.