Nucleic Acids and Biological Macromolecules Study Guide

Nucleic Acids and Biological Macromolecules Study Guide 1. Nucleic Acids Structure and Components • Nucleic acids encode biological information in sequences of nucleotide monomers • Each nucleotide has three structural components: 1. Five-carbon sugar (deoxyribose or ribose) 2. Phosphate group 3. Nitrogenous base (adenine, thymine, guanine, cytosine, or uracil) • DNA and RNA have different structures and functions DNA vs RNA • Structural differences: 1. DNA contains deoxyribose; RNA contains ribose 2. DNA uses thymine; RNA uses uracil 3. DNA is usually double-stranded; RNA is usually single-stranded 4. DNA strands are antiparallel • Both DNA and RNA have a 5’ to 3’ orientation Base Pairing • Adenine pairs with thymine (DNA) or uracil (RNA) • Cytosine pairs with guanine • In DNA, base pairs are held together by hydrogen bonds (A-T: 2 bonds, C-G: 3 bonds) Directionality and Synthesis • Nucleic acids have 5’ and 3’ ends • During synthesis, nucleotides are added to the 3’ end of the growing strand 2. Proteins Amino Acids • • • • Building blocks of proteins Have an amino (NH2) terminus and a carboxyl (COOH) terminus 20 different amino acids, differentiated by their R groups (side chains) R groups can be hydrophobic, hydrophilic, or ionic Protein Structure 1. Primary structure: Sequence of amino acids 1 2. Secondary structure: Local folding (alpha-helices and beta-pleated sheets) 3. Tertiary structure: Overall 3D shape due to R group interactions 4. Quaternary structure: Interactions between multiple polypeptide units Protein Synthesis • Amino acids are joined by dehydration synthesis, forming peptide bonds • Synthesis occurs from the amino to the carboxyl terminus Protein Denaturation • Loss of native conformation due to changes in pH, temperature, or other factors • Denatured proteins are biologically inactive 3. Carbohydrates Types and Functions • Include simple sugars (monosaccharides) and polymers (polysaccharides) • Functions: Fuel, building material, storage, structure Structure • Monosaccharides: Basic units (e.g., glucose, fructose) • Disaccharides: Two monosaccharides joined (e.g., sucrose) • Polysaccharides: Many monosaccharides joined (e.g., starch, cellulose, glycogen) Synthesis and Breakdown • Joined by dehydration synthesis (condensation reaction) • Broken down by hydrolysis 4. Lipids Characteristics • Do not form polymers • Hydrophobic due to hydrocarbon components • Main types: Fats, phospholipids, steroids Fats (Triglycerides) • Composed of glycerol and three fatty acids • Saturated fats: No double bonds, solid at room temperature • Unsaturated fats: Have double bonds, liquid at room temperature 2 Phospholipids • Have polar (hydrophilic) heads and nonpolar (hydrophobic) tails • Form bilayers in cell membranes Steroids • Four fused carbon rings • Examples: Cholesterol, sex hormones 5. Elements of Life Carbon • Forms the backbone of biological molecules • Can form four covalent bonds, allowing for diverse molecule formation Other Important Elements • Nitrogen: Used in proteins and nucleic acids • Phosphorus: Used in nucleic acids and some lipids 6. Water and Its Properties Structure • Composed of two hydrogen atoms and one oxygen atom • Polar molecule due to unequal electron sharing Hydrogen Bonding • Occurs between water molecules • Responsible for many of water’s unique properties Important Properties 1. 2. 3. 4. Cohesion: Attraction between water molecules Adhesion: Attraction between water and other substances Surface tension: Resistance of water’s surface to rupture High specific heat: Ability to absorb or release heat with minimal temperature change 5. Lower density as a solid: Ice floats on liquid water 6. Universal solvent: Can dissolve many polar and ionic substances Hydrophilic vs Hydrophobic • Hydrophilic: Has an affinity for water • Hydrophobic: Does not have an affinity for water 3 7. Synthesis and Breakdown of Polymers Dehydration Synthesis (Condensation Reaction) • Joins monomers to form polymers • Removes a water molecule in the process Hydrolysis • Breaks down polymers into monomers • Adds a water molecule in the process 4