lecture chemistry of Carbohydrate

Chemistry of Carbohydrates

Introduction

  • Carbohydrates are crucial biomolecules found in all living organisms.

Four Main Families of Biomolecules in Cells

  • Carbohydrates

  • Proteins

  • Lipids

  • Nucleic Acids (DNA and RNA)

    • Innate / Genetic Functions

    • Acquired / Metabolic Functions

Definition

  • Carbohydrates are defined as polyhydroxy aldehydes or ketones, or compounds yielding these on hydrolysis.

General Characteristics

  • Etymology: The term carbohydrate comes from the French "hydrate de carbone."

  • Composed of Carbon (C), Hydrogen (H), and Oxygen (O).

  • General empirical formula: (CH₂O)n (Example: C₆H₁₂O₆ when n=6).

  • Exceptions exist (e.g., deoxysugars, aminosugars).

Functions of Carbohydrates

  • Source of Energy: Primary fuel for biological processes.

  • Reserve Material: Stored as glycogen in animals and starch in plants.

  • Structural Role: Supports cellular structures, e.g., cellulose.

  • Digestive Benefits: Dietary fibers aid in digestion and muscle support.

  • Amino Acid Formation: Contributes to amino acid synthesis.

Biochemical Importance

  • Glucose: Major carbohydrate, essential in metabolism and energy production, significantly stored in the liver.

Classification of Carbohydrates

  • Monosaccharides: Simple sugars, single aldose or ketose group, cannot be hydrolyzed further.

    • Examples: Triose, Tetrose, Pentose, Hexose

  • Oligosaccharides: Composed of 2-10 monosaccharide units.

  • Polysaccharides: Composed of many monosaccharide units, includes starch, glycogen, cellulose.

  • Derived Sugars: Acid sugars, amino sugars, deoxy sugars.

Monosaccharides

General Characteristics

  • Simple sugars with one carbonyl group (aldehyde or ketone).

  • Cannot be hydrolyzed into simpler sugars.

Common Monosaccharides Examples

  • Trioses: Glyceraldehyde, Dihydroxyacetone

  • Tetroses: Erythrose, Erythrulose

  • Pentoses: Ribose, Ribulose

  • Hexoses: Glucose, Fructose

Biological Importance of Hexoses

  • D-Glucose: Found in starch and fruits, provides energy.

  • D-Galactose: Found in dairy, forms glycoproteins and glycolipids.

  • D-Fructose: Found in fruits, converted to glucose.

  • D-Mannose: Present in plans, plays role in glycoprotein synthesis.

Structures of Monosaccharides

  • Fischer Projection: Linear representations.

  • Haworth Projection: Cyclic representations, forms furanose and pyranose rings.

Anomers and Mutarotation

  • Anomers: Isomers differing in configuration at the anomeric carbon.

  • Mutarotation: The interconversion of anomers in solution, influencing optical activity.

Disaccharides

  • Formed by the condensation of two monosaccharides, can be reducing or non-reducing sugars.

  • Examples:

    • Sucrose: glucose + fructose (non-reducing)

    • Lactose: glucose + galactose (reducing)

    • Maltose: glucose + glucose (reducing)

Oligosaccharides

  • Yield several monosaccharides upon hydrolysis.

  • Raffinose: Composed of glucose, fructose, and galactose.

  • Stachyose: Composed of multiple monosaccharides.

Polysaccharides

General Characteristics

  • Large polymers, can be branched or unbranched.

  • Homopolysaccharides: Composed of the same type of monosaccharide (e.g., starch, glycogen).

  • Heteropolysaccharides: Composed of different types of monosaccharides (e.g., hyaluronic acid).

Starch

  • Major dietary carbohydrate from plant sources.

  • Two types: amylose (unbranched) and amylopectin (branched).

Glycogen

  • Storage form of glucose in animals; highly branched for rapid mobilization.

Cellulose

  • Composed of glucose units with β(1-4) linkages; indigestible by humans but important for digestive health.

Importance of Glycosaminoglycans (GAGs)

  • Structures important for lubrication and shock absorption in the body.

  • Include hyaluronic acid, chondroitin sulfate, and heparin.

Disorders Related to Carbohydrates

  • Diabetes Mellitus: Impaired carbohydrate metabolism.

  • Lactose Intolerance: Insufficient lactase enzyme to digest lactose from dairy.

  • Glycogen Storage Diseases: Genetic disorders affecting glycogen metabolism leading to muscle weakness and hypoglycemia.

Summary

  • Carbohydrates are essential biomolecules involved in energy, structure, and metabolic regulation, classified into monosaccharides, oligosaccharides, disaccharides, and polysaccharides, fundamentally impacting health and nutrition.