Basic of Biochemistry: Carbohydrates and Lipids

Carbohydrates and Glycobiology

• Syllabus topics: monosaccharides, disaccharides, polysaccharides, structure and function of biologically important sugar derivatives, digestion of carbohydrates, fats, and proteins in the body
• Objectives: differentiate between monosaccharides, disaccharides, oligosaccharides, and polysaccharides, understand chirality, stereoisomers, enantiomers, epimers, and anomers, recognize reducing and non-reducing sugars, draw and name simple carbohydrates using structural formulas, Fischer and Haworth projection formulas

Nomenclature

• Simple carbohydrates can be classified based on the number of carbon atoms (e.g., triose, pentose, hexose) or functional group (e.g., ketose, aldose)
• Polysaccharides can be classified by the number of sugar molecules in the chain (e.g., monosaccharide, disaccharide, trisaccharide)

Classification

• Monosaccharides: consist of one sugar containing 3, 4, 5, 6, or 7 carbon atoms
• Disaccharides: composed of two monosaccharides
• Oligosaccharides: contain a small number (typically 3-10) of monosaccharides
• Polysaccharides: polymers made up of many monosaccharides linked by glycosidic bonds

Monosaccharides

• Monosaccharides are colorless, crystalline solids that are freely soluble in water but insoluble in nonpolar solvents
• They have a sweet taste
• Examples: glucose, ribose, deoxyribose

Fischer Projection

• A method of representing the three-dimensional structure of a molecule in a two-dimensional format
• Used to show the arrangement of atoms in a molecule

Enantiomers and Epimers

• Enantiomers: non-superimposable mirror images of each other
• Epimers: monosaccharides that differ in configuration at only one carbon atom

Glucose

• Exists in a cyclic α-D-glucose form and an open chain conformation
• Can be found in an aqueous solution as a mixture of α-D-glucose and β-D-glucose

Polysaccharides

• Homopolysaccharides: polymers containing a single type of monosaccharide (e.g., starch, glycogen, cellulose, chitin)
• Heteropolysaccharides: polymers containing more than one type of monosaccharide (e.g., peptidoglycan)

Energy Storage Polysaccharides

• Starch: found in plant cells, composed of amylose and amylopectin
• Glycogen: found in animal cells

Structural Polysaccharides

• Cellulose: found in plant cell walls, composed of thousands of repeating glucose units connected by β1-4 glycosidic bonds
• Chitin: found in the exoskeleton of animals, composed of repeating N-acetylglucosamine units linked by β1-4 glycosidic bonds

Glycoconjugates

• Consist of a small number of carbohydrate units (oligosaccharides) covalently attached to a core protein
• Examples: peptidoglycans, proteoglycans, glycoproteins

Proteoglycans and Glycoproteins

• Proteoglycans: contain glycosaminoglycans (GAGs) such as hyaluronic acid, chondroitin sulfate, and heparan sulfate
• Glycoproteins: contain oligosaccharides attached to a protein backbone

Structure of Cell Membrane and Glycoproteins

• Glycoproteins play a role in cell-cell recognition and adhesion
• The influenza virus recognizes sialic acid residues on glycoproteins

Importance of Glycobiology

• Glycans play a crucial role in various biological processes and are implicated in many diseases
• The "glycome" is considered the next big thing in health and medicine
• Nobel Prize in Chemistry 2022 was awarded for contributions to the field of glycobiology

This quiz covers the basics of biochemistry, focusing on carbohydrates, glycobiology, and lipids. It includes topics such as monosaccharides, disaccharides, polysaccharides, and biologically important sugar derivatives.