Macromolecules: Structure, Function, and Subunits Review

Introduction

• Four types of macromolecules: carbohydrates, lipids, proteins, nucleic acids

Carbohydrates

• Structure: empirical formula CH2O
• Types: Monosaccharides (glucose, fructose, galactose), disaccharides (sucrose)
• Monosaccharides: Monomer units of carbohydrates
  • Glucose: Six-carbon sugar, forms a six-membered ring, aldohexose
  • Fructose: Six-carbon sugar, forms a five-membered ring, ketohexose
  • Galactose: Monosaccharide, stereoisomer of glucose (differ at carbon 4)
• Polysaccharides: Many sugar units (e.g. starch, glycogen, chitin, cellulose)
  • Starch: Energy storage in plants (amylose - straight; amylopectin - branched)
  • Glycogen: Energy storage in animals, highly branched
  • Chitin: Structural material in insects

Proteins

• Monomers: Amino acids
• Functions: Enzymatic, structural, transport, etc.
• Amino Acids: Identified by amino group, carboxyl group, hydrogen atom, variable R group
  • Nonpolar aromatic: Phenylalanine (nonpolar, contains benzene ring)
• Protein Structures: Primary (sequence of AA), Secondary (α-helix and β-sheet), Tertiary (3D folding), Quaternary (subunits like in hemoglobin)

Lipids

• Types: Triglycerides, phospholipids, steroids
  • Triglycerides: Long-term energy storage (saturated - solids, unsaturated - liquids)
  • Phospholipids: Form cell membranes (polar head, two non-polar tails)
  • Steroids: Four fused rings (e.g., cholesterol, testosterone)
• Example Functions: Cell membrane structure, energy storage, thermal insulation

Nucleic Acids

• Types: DNA, RNA
• Components: Phosphate groups, ribose sugar, nitrogenous bases (purines - adenine, guanine; pyrimidines - cytosine, thymine, uracil)
• DNA vs RNA: DNA contains deoxyribose sugar, RNA contains ribose sugar

Summary & Key Points

• Enzymes: Proteins that catalyze reactions typically end in “-ase” (e.g., lactase, amylase)
• Hormones Not Proteins: Testosterone (steroid hormone)
• Lipids vs Proteins/Nucleic Acids: Lipids generally do not contain P (except phospholipids), proteins/nucleic acids do contain N

Final Notes

• Macromolecule structural details: Denotation of chains and bonds (alpha, beta linkages)
• Functional groups: Importance of functional groups like OH, NH (polarity)
• Examples and mnemonic tools: Recognize by suffixes (-ose for sugars, -in for proteins/enzymes)
  • E.g., Amylose (alpha 1-4 linkage), Cellulose (beta 1-4 linkage)