Organic Compounds

Organic Compounds

The Molecules of Life

• Most important large molecules in living things

• Three classes key to life: carbohydrates, proteins, nucleic acids

• Macromolecules: large biological molecules like proteins exhibiting emergent properties from atom arrangement

Macromolecules and Polymers

• Polymers: Long molecules consisting of many similar units (monomers) linked by covalent bonds (analogy: train of cars)

• Monomers: Smaller repeat units that serve as building blocks of polymers

Synthesis and Breakdown of Polymers

• Enzymes: Specialized macromolecules that speed up reactions

• Dehydration Reaction: Joins monomers by losing a water molecule; one monomer contributes -OH, the other -H

• Hydrolysis: Reverse of dehydration; water breaks down polymers into monomers

• Example: Food digestion breaks polymers into usable monomers through hydrolysis

Carbohydrates: Fuel and Building Material

• Includes sugars and sugar polymers

• Monosaccharides: Simplest carbohydrates, single sugar units

• Disaccharides: Two monosaccharides linked by a covalent bond (glycosidic linkage)

• Polysaccharides: Long chains of monosaccharides (e.g., starch), serve as energy storage or structures

Diversity of Polymers

• Cells contain thousands of macromolecules with variations across types

• Genetic variations reflected through diversity in DNA and proteins

• Vast number of macromolecule combinations arise from 40-50 common monomers (like 26 letters forming words)

Sugars and Their Functions

• Monosaccharides: Major cellular nutrients, used in cellular respiration to extract energy

• Form disaccharides/polysaccharides for storage

Disaccharides Example

• Maltose: Formed from glucose molecules; used in brewing

• Sucrose: Common sugar made of glucose and fructose

• Lactose: Sugar in milk; requires lactase to digest; lactose intolerance occurs due to lack of enzyme

Polysaccharides

• Macromolecules with hundreds to thousands of sugar units joined by glycosidic linkages

• Serve as energy reserves (starch/glycogen) or structural materials (cellulose/chitin)

Storage Polysaccharides

• Starch: Stored form of glucose in plants, can be hydrolyzed for energy

• Glycogen: Storage form in animals, more branched than starch

Structural Polysaccharides

• Cellulose: Major component of plant cell walls; not hydrolyzed by digestive enzymes in humans

• Chitin: Found in exoskeletons of arthropods and fungal cell walls

Lipids: Diverse Hydrophobic Molecules

• Lipids differ from macromolecules; not true polymers, hydrophobic due to hydrocarbon structure

• Includes fats, phospholipids, steroids

Fats

• Constructed from glycerol and fatty acids through dehydration reactions

• Saturated Fats: No double bonds, solid at room temperature (e.g., animal fats)

• Unsaturated Fats: One or more double bonds, liquid at room temperature (e.g., vegetable oils)

Phospholipids

• Key component of cell membranes; form bilayers in aqueous environments due to hydrophilic heads and hydrophobic tails

Steroids

• Lipids with a four-ring carbon structure (e.g., cholesterol is essential for cell membranes)

Proteins: Diverse Structures and Functions

• Proteins are formed from 20 amino acids; each has unique functions and structures

• Functions: Enzymatic, defensive, storage, transport, hormonal, receptor, structural, contractile

• Enzymatic Proteins: Catalyze reactions, e.g., digestive enzymes

• Structural Proteins: Support cells and tissues, e.g., collagen in connective tissue

Protein Structure

• Proteins have four levels of structure: primary (amino acid sequence), secondary (coils and folds), tertiary (overall shape), and quaternary (combination of polypeptides)

• Denaturation: Loss of natural shape due to environmental changes, making proteins inactive

Nucleic Acids: DNA and RNA

• Store, transmit, and express hereditary information

• DNA directs RNA synthesis, controlling protein synthesis

  • Nucleotides: Building blocks of nucleic acids, composed of sugar, nitrogenous base, and phosphate groups

Structure of Nucleic Acids

• DNA: Double helix form, antiparallel strands held by hydrogen bonds between paired bases (A-T, G-C)

• RNA: Single-stranded, variable in shape, aids in protein synthesis

Summary

• Organic compounds such as carbohydrates, lipids, proteins, and nucleic acids are essential for life, each performing unique and vital functions.