CHM 330 Exam 1: Comprehensive Biochemistry Study Guide

Module 1: Foundations of Biochemistry

Review of Organic Compounds

Organic compounds are the chemical foundation of biochemistry, primarily composed of carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus. Understanding their structure and reactivity is essential for studying biomolecules.

• Functional Groups: Key groups include hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate. These determine the chemical properties and reactivity of biomolecules.

• Isomerism: Structural isomers differ in connectivity; stereoisomers differ in spatial arrangement (e.g., enantiomers and diastereomers).

• Example: Glucose and fructose are structural isomers (both C6H12O6).

Review of Eukaryotes and Prokaryotes

Cells are classified as prokaryotic or eukaryotic based on structural features.

• Prokaryotes: Lack a nucleus and membrane-bound organelles; include bacteria and archaea.

• Eukaryotes: Possess a nucleus and organelles (e.g., mitochondria, ER); include animals, plants, fungi, and protists.

• Comparison Table:

Feature	Prokaryotes	Eukaryotes
Nucleus	No	Yes
Organelles	No	Yes
Cell Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria	Animals, Plants

Review of Aqueous Chemistry

Water's unique properties and its role as a solvent are central to biochemistry.

• Intermolecular Forces: Hydrogen bonding, van der Waals forces, ionic interactions.

• Water Structure: Polar molecule, forms extensive hydrogen bonds, high heat capacity.

• pH and pKa: pH measures hydrogen ion concentration; pKa is the acid dissociation constant.

• Solubility: Polar and ionic compounds dissolve well in water; nonpolar compounds are hydrophobic.

• Key Equations:

$\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

$\mathrm{p}K_a = -\log_{10}K_a$

$\mathrm{Henderson-Hasselbalch:}\quad \mathrm{pH} = \mathrm{p}K_a + \log_{10}\left(\frac{[A^-]}{[HA]}\right)$

Amino Acids and Peptides

Amino acids are the building blocks of proteins, each with unique side chains affecting structure and function.

• Classification: Based on side chain properties: nonpolar, polar uncharged, acidic, basic.

• Ionization: Amino acids can exist as zwitterions at physiological pH.

• L vs D: Most natural amino acids are L-isomers.

• pKa Values: Each amino acid has characteristic pKa values for the α-carboxyl and α-amino groups, and sometimes the side chain.

• Isoelectric Point (pI): The pH at which the amino acid has no net charge.

• Peptide Formation: Peptide bonds form via condensation reactions between amino and carboxyl groups.

• Titration Curves: Show the ionization states of amino acids as pH changes.

• Example: Glycine has pKa values of ~2.3 (COOH) and ~9.6 (NH2); pI ≈ 6.0.

Proteins: Structure and Determination

Proteins are polymers of amino acids with complex structures essential for biological function.

• Primary Structure: Linear sequence of amino acids.

• Secondary Structure: Local folding patterns: α-helix, β-sheet, β-strand, β-hairpin.

• Tertiary Structure: 3D folding of a single polypeptide chain.

• Quaternary Structure: Association of multiple polypeptide chains (oligomeric proteins).

• Disulfide Bonds: Covalent bonds between cysteine residues stabilize structure.

• Globular Proteins: Compact, water-soluble proteins (e.g., enzymes, hemoglobin).

• Protein Determination: Methods include X-ray crystallography, NMR, and mass spectrometry.

Module 2: Enzymes and Kinetics

Enzyme Catalysis and Classification

Enzymes are biological catalysts that accelerate chemical reactions with high specificity.

• Catalysis: Enzymes lower activation energy, increasing reaction rates without being consumed.

• Enzyme Classes: Six major classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases.

• Enzyme-Substrate Interactions: Substrate binds to the active site, forming an enzyme-substrate complex.

• Lysozyme: An enzyme that cleaves polysaccharide chains in bacterial cell walls.

• Serine Protease: Enzyme class with a serine residue in the active site; mechanism involves a tetrahedral intermediate.

Enzyme Kinetics and Inhibition

Enzyme kinetics studies the rates of enzyme-catalyzed reactions and how they are affected by various factors.

• Michaelis-Menten Kinetics: Describes the relationship between substrate concentration and reaction rate.

• Key Parameters: $K_m$ (Michaelis constant), $V_{max}$ (maximum velocity), $k_{cat}$ (turnover number), $V_0$ (initial velocity).

• Lineweaver-Burk Plot: Double reciprocal plot used to determine kinetic parameters.

• Inhibitors: Competitive, noncompetitive, uncompetitive; each affects $K_m$ and $V_{max}$ differently.

• Inhibition Constant ($K_i$): Quantifies inhibitor potency.

• Noncovalent Modifications: Allosteric regulation, feedback inhibition.

• Reaction Order: Zero, first, or second order depending on substrate concentration.

• Key Equations:

$V_0 = \frac{V_{max}[S]}{K_m + [S]}$

$\frac{1}{V_0} = \frac{K_m}{V_{max}} \cdot \frac{1}{[S]} + \frac{1}{V_{max}}$

Zymogens and Activation

Zymogens are inactive enzyme precursors that require modification to become active.

• Activation: Often involves proteolytic cleavage (e.g., trypsinogen to trypsin).

• Regulation: Ensures enzymes are active only when and where needed.

Module 3: Carbohydrates, Lipids, Membranes, and Signaling

Carbohydrate Structure and Stereochemistry

Carbohydrates are classified by their carbonyl group and stereochemistry.

• D vs L Configuration: Refers to the orientation of the chiral center farthest from the carbonyl group.

• Aldoses vs Ketoses: Aldoses have an aldehyde group; ketoses have a ketone group.

• Projections: Fischer (linear), Haworth (cyclic), and chair (3D) representations show stereochemistry.

• Epimers: Differ at one chiral center (e.g., glucose and galactose).

• Anomeric Carbon: The new chiral center formed upon cyclization; α and β anomers differ in configuration.

Di- and Polysaccharide Classification

Carbohydrates can form larger structures through glycosidic bonds.

• Disaccharides: Two monosaccharides linked (e.g., sucrose, lactose).

• Polysaccharides: Long chains (e.g., starch, glycogen, cellulose).

• Lectins: Proteins that bind specific carbohydrate structures, important in cell recognition.

Lipids and Fatty Acids

Lipids are hydrophobic molecules essential for energy storage, membranes, and signaling.

• Fatty Acid Melting Point: Increases with chain length, decreases with unsaturation (double bonds).

• Common Lipid Structures: Triacylglycerides (energy storage), phosphatidic acid (membrane precursor), lipoproteins (transport), eicosanoids (signaling), steroids (hormones), cholesterol (membrane fluidity).

Biological Membranes and Transport

Membranes are lipid bilayers with embedded proteins, controlling the movement of substances.

• Active vs Passive Transport: Passive does not require energy (diffusion, facilitated diffusion); active requires energy (pumps, transporters).

• Types of Transporters: Channels, carriers, pumps.

• Neurotransmitters: Chemical messengers released at synapses, often requiring specific transport mechanisms.

Cell Signaling and Receptor Proteins

Cells communicate via signaling molecules and receptor proteins, triggering intracellular responses.

• Receptor Protein Signaling: Ligand binding activates receptors, initiating signal transduction.

• cAMP: Cyclic AMP, a second messenger in many signaling pathways.

• G-Proteins: Guanine nucleotide-binding proteins that relay signals from receptors to effectors.

Redox Reactions and Cofactors

Oxidation-reduction (redox) reactions are fundamental to metabolism.

• Reducing Agents: Donate electrons; Oxidizing Agents: Accept electrons.

• Cofactors: Non-protein molecules (e.g., NAD+, FAD) required for enzyme activity.

• Oxidation Number: Indicates the degree of oxidation of an atom in a compound.