Final Exam Review

Key Concepts from Chapters 2-6 for Exam I

Rutherford Experiment

• Utilized gold foil to scatter α-particles, demonstrating the existence of the atomic nucleus.

Atomic Structure

• Atoms are electrically neutral: number of protons equals the number of electrons (atomic number).

• Elements: substances that cannot be broken down by chemical means.

• Mass vs. Weight: Mass is constant (same on Earth and Moon), while weight varies due to gravity.

• Mass of subatomic particles: Proton and neutron approximately equal 1 dalton.

• 1 gram = 6.02 x 10²³ daltons.

Ionic and Molecular Structures

• Cation: More protons than electrons.

• Anion: More electrons than protons.

• Isotopes: Same element with different neutron counts (e.g., C12, C13).

• Radioactive Isotopes: Unstable, decay at a constant rate (half-life).

• Chemical nature dictated by electrons in the outermost orbital (valence orbital).

• Electrons occupy discrete energy levels (K, L, etc.); each orbital can hold a maximum of 2 electrons.

Electronegativity and Water Properties

• Electronegativity: Atom's affinity for electrons (O = 3.5, N = 3.0, C = 2.5, H = 2.1).

• Water is a polar molecule due to electronegativity differences, with hydrogen bonding favored between O-acceptors and H-donors.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other polar molecules (e.g., glass).

• Water influences hydrophilic and hydrophobic interactions, enabling structures like monolayers and micelles.

• pH: Water is almost neutral (1 in 10 million ionizes). Acids are proton donors, bases are proton acceptors.

• Buffers: Mixture of weak acid and salt to stabilize pH.

Functional Groups

• Primary: Hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate.

• Secondary: Ester, thioester, ether, thioether, amide, anhydride.

Structural Relationships

• Structural Isomers: Different structures of a carbon skeleton.

• Stereoisomers: Differ in group attachment; Enantiomers are chiral mirror images.

Biomolecules

Macromolecules

• Polymers (carbohydrates, nucleic acids, proteins) composed of monomers.

• Created by dehydration synthesis; broken down by hydrolysis.

Carbohydrates

• Monosaccharides: Simple sugars (3–9 carbons, with carbonyl and hydroxyl groups).

• Oligo- and polysaccharides: Called glycans.

• D-glucose: Linear structure with 4 stereocenters; cyclization creates additional stereocenter (α, β).

• Disaccharides: αD-glucose + αD-fructose = sucrose; αD-glucose + αD-glucose = maltose.

• Starch: Polymer of glucose, consists of amylose (1-4 link) and amylopectin (1-4 & 1-6 link).

• Cellulose: Linear polymer of βD-glucose.

Nucleotides and Nucleic Acids

• Nucleotide structure: sugar + nitrogenous base + phosphate.

• Essential for DNA/RNA: DNA (deoxyribose), RNA (ribose) with single phosphate.

• Nucleic Bases: Purines (adenine & guanine) and pyrimidines (cytosine, thymine, uracil).

• DNA structure: Double helix with base pairing A:T and C:G.

• RNA function: Carries information from DNA for protein synthesis.

Proteins

• Composed of 20 α-amino acids (all in L-form).

• Protein Structure Levels:

  • Primary: Protein sequence.

  • Secondary: α-helix or β-sheet.

  • Tertiary: Final shape (globular or fibrous).

  • Quaternary: Complex of 2 or more tertiary structures.

• Protein Folding: Guided by chaperones; native state is functional structure.

• Functional Domains: Specific regions with distinct functions like catalysis.

Lipids

Triglycerides and Phospholipids

• Triglycerides: Esters of glycerol with 3 fatty acids (12-20 carbons; animal unsaturated are cis).

• Phospholipids: Comprise glycerol + 2 fatty acids + phosphate; amphiphilic properties.

Cell Structure

Cell Basics

• Cells: Basic units of organisms; arise from existing cells.

• Historical Discovery: Robert Hooke (1665) first observed cells.

• Microscopes: Light and electron types; electron microscopy for higher resolution.

• Basic Cell Structures: Nucleoid/nucleus, cytoplasm, ribosomes, plasma membrane.

Prokaryotes vs. Eukaryotes

• Prokaryotes: No membrane-bound nucleus, found in Archaea and Bacteria.

• Archaea have cell walls composed of sugars/proteins; Bacteria have peptidoglycan walls.

• Eukaryotes: Contain nucleus with linear chromosomes and nucleolus for RNA synthesis.