Lecture Overview

• Reading: Ch7; 220-235
• Problems: Ch7; 1,2,3,5,9
• Next Reading: Ch7; 236-241, 251-254, 258-260
• Next Problems: Ch7; 4,6,7,8,13,14,15,18,16,17,25,27

Carbohydrates

Definition

• Formula: Cn(H2O)_n for n ext{ ≥ } 3
• Monosaccharides are precursors to polysaccharides

Roles

• Energy source/storage: glucose, fructose, starch, glycogen
• Structure: cellulose, chitin
• Information: ribose in nucleotides
• Recognition: glycolipids, glycoproteins

Chemistry of Monosaccharides

Chirality

• Asymmetric carbons lead to chiral forms
• Can exist in linear and ring forms

Derivatives

Oxidation

• C1: forms onic acids
• C6: forms uronic acids

Reduction

• Aldehyde/ketone to alcohol: forms sugar alcohols
• Can reduce alcohol carbon (deoxysugars)

Ester Formation

• Forms sugar phosphates, important in biochemistry

Amino Sugars

• Formed through condensation with ammonia, often modified

Polymerization

Glycosidic Bond

• Stable bonding between sugars, formed via hemiacetal/hemiketal and hydroxyl carbon
• Nonreducing anomeric carbon involved in linkage

Oligosaccharides

• Examples include glycoproteins, glycolipids, with specific linkages, e.g., O- and N-linked

Polysaccharides

Types

• Homopolysaccharides: starch, glycogen, cellulose, chitin
• Heteropolysaccharides: multiple monomer units, linear or branched
• High molecular weight, often insoluble due to size

Glycogen and Starch

• Glycogen: branched glucose polymer, energy storage
• Starch: mixture of amylopectin (branched) and amylose (unbranched)

Cellulose and Chitin

Cellulose

• Linear, tough structure, insoluble, composed of beta (1→4) linkages
• Major component of plant cell walls, difficult to digest for most animals

Chitin

• Linear polymer of N-acetylglucosamine, forms flexible structures, found in exoskeletons.