Biochemistry HBF-102 Carbohydrate Chemistry

Carbohydrate Chemistry Lecture Notes

• Course: Biochemistry for Year 1 students, HBF-102
• University: Helwan National University
• Semester: 1, 2024/2025
• Module: Human body Function (HBF) 102
• Lecturer(s): Dr. Mohamed I. Kotb & Dr. Ahmed M. A. Akabawy.
• Department: Biochemistry & Molecular Biology, Faculty of Pharmacy, Helwan University.

Carbohydrate Chemistry I

• Objectives:
  • Define carbohydrates and their biological importance.
  • Classify carbohydrates.
  • Define, classify, and describe the structural composition of monosaccharides.
  • Describe the biological importance of monosaccharides.
  • Define isomerism and their different forms with examples.
  • List monosaccharides derivatives.

Introduction to Carbohydrates

• Carbohydrates are the most abundant organic biomolecules in nature.
• CHO (Carbohydrates) are aldehydic or ketonic derivatives of polyhydric alcohols.
• General empirical formula is [C(H₂O)]n .

Classification of Carbohydrates

• Classified into:
  • Monosaccharides: Cannot be hydrolysed into simpler units.
  • Disaccharides: Produce two molecules of monosaccharides on hydrolysis.
  • Oligosaccharides: Produce three to ten monosaccharide units on hydrolysis.
  • Polysaccharides: Produce more than ten monosaccharide units on hydrolysis.

Examples of Monosaccharides

• Hexoses:
  • Glucose
  • Fructose
  • Galactose.
• Pentoses:
  • Ribose
  • Xylose

Examples of Disaccharides

• Lactose: Formed of galactose and glucose with a β1,4-glycosidic linkage, found in milk.
• Maltose: Formed from two glucose units with an α1,4-glycosidic linkage, a product of starch digestion.
• Sucrose: Formed from glucose and fructose with a 1,2-glycosidic linkage.

Examples of Polysaccharides

• Starch: The chief storage form of carbohydrates in plants, made of glucose units by glycosidic bonds.
• Glycogen: The storage form of carbohydrates in animals, highly branched polysaccharide made of glucose units, branching points connected by α1,6-glycosidic linkages.
• Cellulose : A long, non-branched chain of β-glucose units with β1,4-glycosidic linkages, important component of plant cell walls.

Classification of Monosaccharides

• Based on the number of carbon atoms:
  • Trioses (3 carbons)
  • Tetroses (4 carbons)
  • Pentoses (5 carbons)
  • Hexoses (6 carbons)
• Based on the carbonyl group:
  • Aldoses: Contain an aldehyde group.
  • Ketoses: Contain a ketone group.

Isomerism

• Isomers are compounds with the same molecular formula but different structures.
• Types of isomerism:
  • Structural Isomerism: Compounds with the same molecular formula but different structural arrangement of atoms.
  • Stereoisomerism: Compounds differing in the spatial arrangement of atoms.
    • Enantiomers: Non-superimposable mirror images.
    • Diastereomers: Stereoisomers that are not mirror images.
      • Epimers: Differ in configuration at only one chiral center.
      • Anomers; Differ in configuration at the anomeric carbon

Chemical Nature of CHO

• CHO (Carbohydrates) are aldehydic or ketonic derivatives of polyhydric alcohols

Biological Importance of Monosaccharides

• Glucose: The final form of carbohydrate digestion, main source of energy in mammals.
• Fructose: Another source of energy in mammals, found in seminal fluid and fruits.
• Galactose: Converted to glucose in the liver, synthesized in mammary glands, part of many glycoproteins.
• Ribose: Found in nucleotides of RNA and DNA, also in ATP and other high-energy phosphate compounds.

Introduction to the next lecture

• Monosaccharides are linked by glycosidic bonds to form larger structures.
• There are different types of glycosidic bonds.
• Important examples of reducing and non-reducing disaccharides.

This quiz covers the fundamental concepts of carbohydrate chemistry as outlined in the Year 1 Biochemistry course, HBF-102 at Helwan University. Students will explore the classification, structure, and biological significance of carbohydrates, particularly monosaccharides, as well as isomerism and its various forms.