Notes on the Chemistry of Microorganisms

Chemistry of Microorganisms - In Depth Notes

Biomolecules

  • Definition: Molecules produced by living organisms, includes both large polymeric molecules like proteins, polysaccharides, lipids, nucleic acids, and smaller molecules such as primary/secondary metabolites, and natural products.

  • Major Constituents:

  • Carbon (C)

  • Hydrogen (H)

  • Oxygen (O)

  • Nitrogen (N)

Biopolymers

  • Definition: Polymers produced by living organisms; formed by covalently bonded monomeric units.

  • Classes: Four main classes based on monomeric units and structure.

Biopolymers vs. Polymers

  • Natural vs. Synthetic: Biopolymers are mostly natural; polymers can be both.

  • Biodegradability: Biopolymers are biodegradable; polymers can be biodegradable or non-biodegradable.

  • Structure: Biopolymers often have well-defined structures, whereas synthetic polymers are simpler or more random.

Major Types of Biomolecules

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic acids

Carbohydrates and Glycoconjugates

  • Abundance: Most abundant biomolecules on Earth; key dietary staple for many.

  • Energy Source: Oxidation of carbohydrates forms the central energy-yielding pathway in non-photosynthetic cells.

  • Structural Role: Carbohydrate polymers serve as protective elements in cell walls of plants and bacteria, and connective tissues in animals.

  • Definition: Polyhydroxy aldehydes or ketones, or yield such substances on hydrolysis. Glycoconjugates are carbohydrate polymers covalently attached to proteins or lipids.

Major Classes of Carbohydrates

  • Monosaccharide:

  • Simple sugars (one unit)

  • Example: D-Glucose is the most abundant.

  • Characteristics: Water-soluble, sweetness varies.

  • Disaccharides:

  • Composed of two monosaccharide units linked by glycosidic bonds.

  • Must be broken down into monosaccharides before absorption.

  • Examples:

    • Sucrose (Glucose + Fructose)

    • Lactose (Glucose + Galactose)

    • Maltose (Two Glucose molecules)

  • Oligosaccharides:

  • Short chains of 2-10 monosaccharides, joined by glycosidic bonds.

  • Example: Fructo-oligosaccharides (FOS), Galactooligosaccharides (GOS)

Polysaccharides

  • Definition: Sugar polymers with more than 20 monosaccharide units; can differ in monosaccharide identity, chain length, bond types, and branching.

  • Examples:

  • Storage Polysaccharides:

    • Starch:

    • Two forms: Amylose (linear) and Amylopectin (branched).

    • Primarily used in energy storage by plants.

    • Glycogen:

    • Main storage form in animals; more branched than starch.

  • Structural Polysaccharides:

    • Cellulose:

    • Composed of β1→4 linked glucose; tough, insoluble.

    • Major component of plant cell walls.

    • Chitin:

    • Composed of N-acetylglucosamine units; forms exoskeleton in arthropods.

    • Peptidoglycan:

    • A heteropolymer forming bacterial cell walls, composed of alternating N-acetylglucosamine and N-acetylmuramic acid.

Glycoconjugates

  • Definition: Carbohydrates linked covalently to proteins or lipids, serving various functions including cellular communication, protein localization, and recognition sites for signals or pathogens.

  • Types of Glycoconjugates:

  • Proteoglycans: Macromolecules with glycosaminoglycan chains linked to proteins; play a role in tissue organization and cellular activities.

  • Glycoproteins: Smaller, branched carbohydrates linked to proteins; important for cell surface recognition and stability.

  • Glycolipids and Lipopolysaccharides: Components of cell membranes with carbohydrate chains on the outer surface.