Comprehensive Study Notes: Organic Chemistry, Chemical Bonding, and Carbohydrates

Course Logistics and Administrative Details

• Class Session Details: The session covering Chapter 3 (Organic Molecules and Macromolecules) includes a worksheet distribution around 1:50 PM.

• Worksheet Timeline: The worksheet cannot be fully completed in a single period. Work continues during the following Tuesday session, and the finalized worksheet is due at the end of class next Tuesday. Emma provides instructional support during these sessions.

Fundamentals of Matter, Elements, and Atomic Structure

• Matter and Elements:

  • Matter: Anything that has mass and occupies space. It is composed of atoms of various elements.

  • Element: The basic building blocks of matter consisting of a single type of atom. Elements possess specific physical and chemical properties and cannot be broken down into simpler substances by standard chemical means.

• Elemental Composition of Life:

  • Four primary elements account for approximately $96\%$ of the mass of all cellular life:

    1. Carbon ($C$)

    2. Nitrogen ($N$)

    3. Oxygen ($O$)

    4. Hydrogen ($H$)

  • Periodic Table Cellular Categorization:

    • Red Group: Carbon, Nitrogen, Oxygen, Hydrogen ($96\%$ of body weight).

    • Blue Group: Commonly found in the human body.

    • Green Group: Essential human nutrients required in trace amounts.

    • Yellow Group: Present in trace amounts; unconfirmed whether essential to human biological function.

• Subatomic Particles and Atomic Architecture:

  • Atom: The smallest structural unit of an element that retains all physical and chemical properties of that element. Composed of a central nucleus surrounded by a cloud of orbiting electrons.

  • Protons: Positively charged particles situated in the nucleus. Each proton has a mass of $1\,\text{atomic mass unit (AMU)}$. The number of protons defines the atomic number and uniquely distinguishes one element from another.

  • Neutrons: Electrically neutral (uncharged) particles situated in the nucleus. Each neutron has a mass of $1\,\text{AMU}$. Neutrons stabilize positive protons within the nucleus; the optimal proton-to-neutron ratio is approximately $1:1$.

  • Electrons: Negatively charged particles orbiting the nucleus within designated electron shells/orbitals. Electrons possess negligible mass (approximately $\frac{1}{1800}$ the mass of a proton or neutron).

  • Neutral Atoms: In an uncharged atom, the number of protons equals the number of electrons, resulting in a net charge of zero.

• Atomic Constants for Key Biological Elements:

  • Hydrogen ($H$): Atomic number $1$ ($1$ proton, $1$ electron).

  • Helium ($He$): Atomic number $2$ ($2$ protons, $2$ neutrons, $2$ electrons).

  • Carbon ($C$): Atomic number $6$ ($6$ protons, $6$ neutrons, $6$ electrons).

  • Nitrogen ($N$): Atomic number $7$ ($7$ protons, $7$ electrons).

  • Oxygen ($O$): Atomic number $8$ ($8$ protons, $8$ electrons).

  • Neon ($Ne$): Atomic number $10$.

  • Sodium ($Na$): Atomic number $11$.

  • Magnesium ($Mg$): Atomic number $12$ ($12$ protons, $12$ electrons).

  • Phosphorus ($P$): Atomic number $15$.

  • Sulfur ($S$): Atomic number $16$.

  • Chlorine ($Cl$): Atomic number $17$.

  • Argon ($Ar$): Atomic number $18$.

  • Potassium ($K$): Atomic number $19$.

  • Calcium ($Ca$): Atomic number 20$.\n* **Atomic Mass and Isotopes:**\n * **Atomic Mass:** Total calculated mass determined by combining the number of protons and neutrons (\text{Protons} + \text{Neutrons}). Reported atomic masses on the periodic table reflect weighted averages across all naturally occurring isotopes.\n * **Isotopes:** Structural variants of an element that maintain the same atomic number (protons) but differ in neutron count.\n * **Carbon Isotopes:**\n * ^{12}C$: Contains$6$protons and$6 neutrons (most abundant).\n * ^{13}C$: Contains$6$protons and$7 neutrons.\n * ^{14}C$: Contains$6$protons and$8$neutrons (natural abundance ratio is approximately$10^{-16}).\n * **Radioisotopes:** Imbalanced proton-to-neutron ratios destabilize the atomic nucleus, causing nuclear decay where the atom emits subatomic particles and/or ionizing radiation.\n* **Electron Shells, Orbitals, and the Octet Rule:**\n * **Orbitals:** Three-dimensional mathematical probability regions around a nucleus where an electron is most likely to be located. Each individual orbital holds a maximum of 2 electrons.\n * **Valence Electrons:** Electrons inhabiting the outermost energy shell (valence shell). These electrons dictate chemical reactivity and bond formation.\n * **Octet Rule:** Biological elements strive for energetic stability by filling their outer valence shells with 8$electrons (with the exception of Hydrogen and Helium, which fill their outer shells with$2 electrons). Atoms share, gain, or lose valence electrons to satisfy this configuration.\n\n# Chemical Bonding and Electronegativity\n\n* **Molecules vs. Compounds:**\n * **Molecule:** Two or more atoms bonded together covalently (can be identical or different elements, e.g., O_2$,$H_2O).\n * **Compound:** A substance composed of two or more *different* elements bonded together in fixed proportions (e.g., H_2O$is a compound;$O_2 is not).\n * **Molecular Formula:** Structural shorthand where chemical symbols represent elements and subscripts indicate exact atom counts (e.g., H_2O indicates 2 Hydrogen atoms and 1 Oxygen atom).\n* **Covalent Bonds:**\n * Formed when two atoms share pairs of valence electrons to complete their outer shells. Shared electrons orbit fluidly through the outer shells of both participating atoms, creating strong chemical links.\n * **Single Covalent Bond:** Sharing of 1$pair of electrons (represented visually by a single solid line$-$, e.g.,$H-F).\n * **Double Covalent Bond:** Sharing of 2$pairs of electrons (represented visually by double solid lines$=$, e.g.,$O=O).\n * **Triple Covalent Bond:** Sharing of 3$pairs of electrons (represented visually by triple solid lines$\equiv$, e.g.,$N \equiv N).\n* **Valence Bonding Capacities of Key Biological Elements:**\n * **Carbon (C$):** Has 4 valence electrons; requires 4 additional electrons. Forms up to$4 covalent bonds (can form 4 single bonds, 2 single bonds + 1 double bond, 1 triple bond + 1 single bond, or 2 double bonds).\n * **Nitrogen (N$):** Has 5 valence electrons; requires 3 additional electrons. Forms$3 covalent bonds.\n * **Oxygen (O$):** Has 6 valence electrons; requires 2 additional electrons. Forms$2 covalent bonds.\n * **Hydrogen (H$):** Has 1 valence electron; requires 1 additional electron. Forms$1 covalent bond.\n* **Electronegativity, Nonpolar Covalent, and Polar Covalent Bonds:**\n * **Electronegativity:** The relative measure of an atom's nuclear attraction for shared electrons within a chemical bond.\n * **Nonpolar Covalent Bonds:** Occur between atoms with identical or very similar electronegativities. Electrons are shared equally between the atoms, leaving no net charge or charge differences across the molecule.\n * *Examples:* Carbon bonded to Carbon (C-C$) or Carbon bonded to Hydrogen ($C-H).\n * *Chemical Nature:* Nonpolar molecules are hydrophobic and insoluble in water.\n * **Polar Covalent Bonds:** Occur between atoms with significantly different electronegativities. Shared electrons spend more time orbiting the nucleus of the more electronegative atom.\n * *Charge Polarity:* Gives the more electronegative atom a partial negative charge (denoted \delta^-$) and the less electronegative atom a partial positive charge (denoted$\delta^+).\n * *Examples:* Oxygen bonded to Hydrogen (O-H$), Nitrogen bonded to Hydrogen ($N-H$), or Carbon bonded to Oxygen ($C-O).\n * *Chemical Nature:* Polar molecules are hydrophilic and readily dissolve in water.\n* **Ionic Bonding:**\n * Occurs when one atom transfers one or more valence electrons completely to another atom, filling the outer shells of both.\n * **Cation:** An atom or molecule that loses electrons, gaining a net positive charge (+).\n * **Anion:** An atom or molecule that gains electrons, gaining a net negative charge (-).\n * **Bond Formation:** Electrostatic attraction between oppositely charged cations and anions creates an ionic bond. Ionic compounds are categorized as salts (e.g., NaCl$,$CaCl_2$,$MgCl_2$,$KCl).\n* **Hydrogen Bonds (H-Bonds):**\n * A weak, non-covalent electrostatic attraction between a partially positive hydrogen atom (\delta^+$) involved in a polar covalent bond and a nearby strongly electronegative atom (typically an Oxygen or Nitrogen bearing a$\delta^- charge).\n * Represented visually in structural diagrams by dotted or dashed lines.\n\n# Properties of Water and Aqueous Solutions\n\n* **Biological Importance of Water:**\n * Water constitutes approximately 70\% of total human body weight and serves as the fundamental liquid solvent of living systems.\n * Functions include acting as a biological solvent, transport medium, mechanical lubricant, chemical reactant, structural force/support provider, waste removal agent, evaporative coolant, and thermal buffer.\n* **Molecular Structure and Hydrogen Bonding in Water:**\n * Water (H_2O$) is a polar molecule: Oxygen attracts shared electrons more strongly than Hydrogen, creating a partial negative charge ($\delta^-$) around Oxygen and partial positive charges ($\delta^+) around both Hydrogens.\n * **Liquid Water State:** Hydrogen bonds between water molecules continually form, break, and reform due to rapid thermal motions. Billions of weak H-bonds shift dynamically on sub-second scales.\n * **Solid Water State (Ice):** Reduced thermal energy prevents the breakage of H-bonds. Water molecules lock into a rigid crystalline lattice maintained by stable hydrogen bonds. This lattice spreads the molecules farther apart, making ice *less dense* than liquid water.\n * **Gaseous State (Boiling Water):** At 100\,^\circ\text{C}$($212\,^\circ\text{F}), thermal energy overrides intermolecular attraction, breaking hydrogen bonds and allowing water molecules to vaporize into gas.\n* **Water as the Universal Solvent:**\n * Water dissolves more substances than any other liquid due to its structural polarity.\n * **Dissolution of Ionic Salts (e.g., NaCl$):** Partially positive Hydrogens in water attract negative Chloride anions ($Cl^-$), while partially negative Oxygens attract positive Sodium cations ($Na^+). These surrounding hydration shells exert enough electrostatic force to pull ionic lattice bonds apart.\n* **Solubility Classifications:**\n * **Hydrophilic ("Water-Loving"):** Dissolve readily in water. Includes ionic compounds (salts) and polar covalent molecules (e.g., sugars, urea CH_4N_2O) that can form hydrogen bonds or electrostatic interactions with water molecules.\n * **Hydrophobic ("Water-Fearing"):** Insoluble in water. Consists of nonpolar, electrically neutral molecules dominated by carbon-hydrogen bonds (e.g., triglycerides, fats, oils, steroids).\n * **Amphipathic ("Both Loves"):** Molecules possessing distinct polar/charged (hydrophilic) regions and nonpolar (hydrophobic) regions. When mixed with water, amphipathic molecules spontaneously assemble into structured configurations such as micelles (e.g., soaps, detergents, phospholipids).\n\n# Acids, Bases, pH Scale, and Buffers\n\n* **Self-Ionization of Water:**\n * In pure water, a small fraction of water molecules spontaneously auto-dissociate at equilibrium by transferring protons:\n\n2H_2O \rightleftharpoons H_3O^+ + OH^-\n\n * This generates equal concentrations of hydronium ions (H_3O^+$, often abbreviated simply as$H^+$) and hydroxide ions ($OH^-).\n* **Acids and Bases:**\n * **Acid:** A solute that increases the relative hydronium ion (H_3O^+$/$H^+) concentration of a solution upon dissociation.\n * *Strong Acid:* Dissociates completely in water, releasing large amounts of H^+.\n * *Weak Acid:* Reversibly/partially donates protons in solution (e.g., carboxyl groups -COOH \rightleftharpoons -COO^- + H^+).\n * **Base:** A solute that decreases the relative H^+ concentration of a solution.\n * *Direct Binding Base:* Accepts protons directly from solution (e.g., ammonia or amino groups -NH_2 + H^+ \rightleftharpoons -NH_3^+).\n * *Hydroxide Base:* Dissociates to generate hydroxide ions (OH^-$), which react with free$H^+ ions to form water.\n* **The pH Scale:**\n * Quantifies the absolute concentration of hydronium ions ([H^+]$) in moles per liter ($mol/dm^3).\n * Logarithmic scale ranging from 0$to$14$: Each single unit change on the pH scale represents a tenfold ($10\times$) shift in$[H^+] concentration.\n * **Neutral Solution (pH = 7$):**$[H^+] = [OH^-] = 10^{-7}\,mol/dm^3 (e.g., pure water).\n * **Acidic Solution (pH < 7$):**$[H^+] > [OH^-].\n * **Basic/Alkaline Solution (pH > 7$):**$[H^+] < [OH^-].\n* **Documented pH Reference Values:**\n * *Battery acid:* 0.5\n * *Stomach acid:* 1.5\n * *Lemon juice:* 2.3\n * *Cola:* 2.5\n * *Orange juice:* 3.5\n * *Beer:* 4.5\n * *Black coffee:* 5.0\n * *Acid rain:* 5.6\n * *Urine:* 6.0\n * *Milk:* 6.5\n * *Pure water:* 7.0\n * *Sea water:* 8.0\n * *Hand soap:* 9.5\n * *Milk of magnesia:* 10.5\n * *Household ammonia:* 11.9\n * *Non-phosphate detergent:* 12.0\n * *Bleach:* 12.5\n * *Caustic soda:* 13.5\n* **Biological Significance of pH and Buffers:**\n * Most intracellular and extracellular biochemical reactions must occur within a strict physiological pH range of 6$to$8.\n * Minor pH shifts alter molecular 3D shape, denature proteins, modify reaction kinetics, disrupt binding affinities, and alter solute solubilities.\n * **Buffers:** Specialized acid-base system solutions that dynamically absorb or release H^+ ions to minimize changes in pH when strong acids or bases enter the system.\n\n# Organic Molecules and Functional Groups\n\n* **Definition of Organic Molecules:**\n * Molecules that explicitly contain carbon-to-hydrogen (C-H$) and/or carbon-to-carbon ($C-C) covalent bonds.\n * Water (H_2O$) and Oxygen gas ($O_2) lack carbon-to-carbon and carbon-to-hydrogen bonds and are categorized as **inorganic**.\n* **Carbon Dynamics and Photosynthesis Context:**\n * The primary stable atmospheric form of carbon is Carbon Dioxide (CO_2).\n * **Photosynthesis:** Autotrophic organisms capture solar electromagnetic energy to fix inorganic CO_2$into organic hexose rings (glucose,$C_6H_{12}O_6).\n * **Chemical Bond Energy:** Significant energy is stored within covalent C-C bonds. Although stable, glucose contains higher potential energy than carbon dioxide.\n * **Cellular Energy Currency:** Cells break down glucose through cellular respiration to produce **Adenosine Triphosphate (ATP)**, the direct universal chemical energy currency utilized by all cellular machinery.\n* **Key Functional Groups:**\n * **Functional Group:** An atom or defined cluster of atoms attached to a carbon backbone (R group, representing "the rest of the molecule") that exhibits identical, consistent chemical properties regardless of the host molecule.\n * **Amino Group (-NH_2):**\n * Acts as a weak base by reversibly binding a free proton (H^+$) from aqueous solution to become$-NH_3^+, reducing overall solution acidity.\n * Found on all amino acids.\n * **Carboxyl Group / Carboxylic Acid (-COOH):**\n * Acts as a weak acid by reversibly donating its proton (H^+$) to water, converting the group to a negatively charged carboxylate ion ($-COO^-).\n * Found on all amino acids and fatty acids.\n * **Hydroxyl Group (-OH):**\n * A strongly polar functional group due to oxygen's high electronegativity.\n * Forms hydrogen bonds with surrounding water molecules, conferring high water solubility and hydrophilicity.\n * Abundant in carbohydrates (sugars), alcohols, steroids, and select amino acids.\n * **Methyl Group (-CH_3):**\n * Composed entirely of nonpolar C-H bonds, rendering it hydrophobic.\n * Covalent attachment of methyl groups to DNA nucleotides (DNA methylation) silences targeted gene expression.\n * **Inorganic Phosphate Group (-PO_4^{2-}):**\n * An inorganic functional group containing a central phosphorus atom bonded to four oxygens, carrying full negative formal charges.\n * Lacks carbon-to-carbon bonds.\n * Highly polar and hydrophilic.\n * Constitutes the polar head of membrane phospholipids, structural backbones of DNA/RNA nucleotides, and energy-carrying tails of ATP. Gives DNA its overall strong negative charge.\n\n# Macromolecular Assembly: Monomers, Polymers, and Reaction Mechanisms\n\n* **Monomer-to-Polymer Paradigm:**\n * **Monomer:** Small, repeating molecular subunits that serve as structural building blocks.\n * **Polymer / Macromolecule:** Large, complex organic structures assembled by covalently linking monomers together.\n * **Scale Examples:**\n * *Proteins:* Assembled from up to 1000+ amino acid monomers linked sequentially.\n * *Chromosomes:* Assembled from long DNA strands containing up to 250\,\text{million} nucleotide base monomers linked end-to-end.\n * *RNA Lifespan:* Transcribed RNA molecules function transiently (lifespans ranging from 5 minutes to 12 hours) before cell hydrolysis degrades them back to free nucleotides.\n* **Dehydration Synthesis / Condensation Reactions:**\n * The universal chemical mechanism used to build polymers by linking monomers one by one.\n * **Mechanism:** A hydroxyl group (-OH$) is removed from one monomer/growing chain while a hydrogen atom ($-H$) is removed from the incoming monomer. These combine to form a free water molecule ($H_2O) released into the environment.\n * A new covalent bond forms directly between the two monomers.\n * **Thermodynamics:** Energetically unfavorable process requiring cellular energy input to drive bond synthesis.\n * **Enzymatic Control:** Catalyzed intracellularly by specific protein enzymes.\n* **Hydrolysis Reactions:**\n * The chemical mechanism used to break polymers down into constituent monomers.\n * **Mechanism:** A molecule of water (H_2O$) is inserted into the polymer bond, splitting into a hydroxyl group ($-OH$) attached to one monomer and a hydrogen atom ($-H) attached to the adjacent monomer.\n * **Thermodynamics:** Energetically favorable process that spontaneously releases energy.\n * **Applications:** Essential for dietary digestion in the small intestine (macromolecules must be broken into monomers before cellular absorption), lysosomal degradation of damaged organelles, RNA recycling, and cleavage of terminal phosphate bonds in ATP to fuel biological work.\n\n# Carbohydrates: Structure, Classification, and Bonding\n\n* **Chemical Definition and Formula:**\n * Carbohydrates represent "hydrated carbon" chains where carbon atoms are bound to hydrogen and oxygen in a ratio identical to water (2:1$ratio of$H:O).\n * General molecular formula: C_n(H_2O)n$or$C_n H{2n} O_n\n* **Monosaccharides (Simple Sugars):**\n * Single sugar units containing a backbone of 3$to$6 carbon atoms:\n * 3 carbons = Triose\n * 4 carbons = Tetrose\n * 5 carbons = Pentose (e.g., Ribose, Deoxyribose)\n * 6 carbons = Hexose (e.g., Glucose, Fructose, Galactose)\n * Standard chemical nomenclature suffix: Sugar names terminate in **"-ose"**.\n * **Structural Chemical Drawing Conventions:** In cyclic ring structural diagrams (e.g., hexagons/pentagons), line intersections (nodes) represent Carbon (C$) atoms unless an explicit non-carbon element symbol (e.g., Oxygen$O$, Nitrogen$N) is labeled.\n* **Disaccharides (Double Sugars):**\n * Molecules created by linking two monosaccharides together via dehydration condensation.\n * Must be broken down by digestive enzymes into monosaccharides before absorption across cell membranes.\n * **Sucrose (Table Sugar):** Assembled from Glucose bonded to Fructose.\n * **Lactose (Milk Sugar):** Assembled from Glucose bonded to Galactose.\n* **Glycosidic Bonds:**\n * The specialized covalent bond formed between two carbohydrate monomers via a dehydration synthesis reaction.\n\n# Overview of Macromolecular Classes\n\n| Macromolecule Class | Primary Monomer Subunit | Primary Biological Functions & Structural Components |\n| :--- | :--- | :--- |\n| **Carbohydrates** | Monosaccharides (e.g., Glucose) | Energy storage (starch, glycogen), structural support, cell identity |\n| **Lipids** | Fatty acids & Glycerol (varies) | High-density energy storage, biological membranes (phospholipids), signaling hormones (steroids: testosterone, estrogen, cholesterol) |\n| **Proteins** | Amino Acids | Catalysis (enzymes), cell structure, molecular transport, signaling (linked via **peptide bonds**) |\n| **Nucleic Acids** | Nucleotides (Bases: A, T, G, C, U) | Information storage and heredity (DNA, RNA) |\n\n# Characteristics of Chemical Reactions\n\n* **Reaction Dynamics:** Processes wherein chemical bonds within reactants are broken and reform to synthesize distinct products (\text{Reactants} \rightarrow \text{Products}$$).

• Core Properties:

  • Require an initial energy input (such as thermal energy/heat).

  • Biological systems utilize specialized protein catalysts called enzymes to accelerate reaction rates.

  • Proceed in defined directional paths toward dynamic chemical equilibrium.

  • Typically occur dissolved within aqueous liquid environments inside cells.