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Biochemistry · 300 Level
This is the complete lecture note for BCH 302 Metabolism of carbohydrate, prepared for Biochemistry students at 300 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course Title: Metabolism of Carbohydrate Course Code: BCH 302 Course Units: 2 Units • Polysaccharides: Structure, Function, and Analysis • Carbohydrate Digestion and Degradation Pathways • Central Metabolic Cycles and Pathways • Gluconeogenesis, Glycogen Metabolism, and Specialized Pathways • Regulation and Disorders of Carbohydrate Metabolism Suggested Outline for Series 1: Polysaccharides: Structure, Function, and Analysis Part 1: Chemistry and Structure of Polysaccharides Monosaccharide building blocks Types of linkages and branching Structural diversity among polysaccharides Part 2: Functions and Biological Roles of Polysaccharides Storage polysaccharides (e.g. starch, glycogen) Structural polysaccharides (e.g. cellulose, chitin) Specialised polysaccharides in biological systems Part 3: Isolation, Purification, and Analytical Methods Techniques for isolation and purification Molecular weight determination Structural analysis methods Part 4: Biochemistry of Disaccharides and Oligosaccharides Important disaccharides (e.g. sucrose, lactose, maltose) Oligosaccharides and their biological significance
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Polysaccharides are among the most abundant biomolecules in nature, forming the structural framework of plants, serving as energy reserves in animals, and playing specialised roles in diverse biological systems. Their study provides a foundation for understanding how carbohydrates are organised, stored, and utilised in living organisms. By examining their chemistry, functions, and methods of analysis, you will gain insights into the essential role polysaccharides play in metabolism and cellular processes. The aim of this Series is to equip you with the knowledge and skills to explain the chemistry and structure of polysaccharides, analyse their biological functions, and describe the techniques used for their isolation, purification, and structural determination. We shall commence this Series by exploring the chemistry and structure of polysaccharides, focusing on their monosaccharide building blocks, linkages, and structural diversity. Next, we will examine their functions and biological roles, including storage and structural polysaccharides as well as specialised forms. Following that, we will study the methods of isolation, purification, and analysis, considering molecular weight determination and structural techniques. Finally, we will conclude by discussing the biochemistry of important disaccharides and oligosaccharides, highlighting their relevance in biological systems. Series Learning Outcomes Upon completing this Series, you should be able to: SLO 1.1 define the monosaccharide building blocks and explain the types of linkages that form polysaccharides, SLO 1.2 analyse the structural diversity of polysaccharides and relate it to their biological functions, SLO 1.3 explain the roles of storage and structural polysaccharides in living organisms, SLO 1.4 describe specialised polysaccharides and evaluate their significance in biological systems, SLO 1.5 demonstrate methods of isolation and purification of polysaccharides, SLO 1.6 apply techniques for molecular weight determination and structural analysis of polysaccharides, and SLO 1.7 explain the biochemistry of important disaccharides and oligosaccharides and assess their relevance in metabolism. 1.1 Chemistry and Structure of Polysaccharides 1.1.1 Monosaccharide building blocks Polysaccharides are long chains of monosaccharides, which are the simplest units of carbohydrates. A monosaccharide is defined as a single sugar molecule that cannot be hydrolysed into smaller carbohydrate units. Common examples include glucose, fructose, and galactose. These molecules serve as the fundamental building blocks from which larger carbohydrate structures are assembled.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The arrangement of monosaccharides in a polysaccharide determines its properties and biological roles. For instance, glucose units linked together form starch or glycogen, while alternating glucose units can form cellulose. Fill in the blank: The simplest unit of carbohydrates that cannot be hydrolysed further is called __________. Short description: Diagram showing glucose, fructose, and galactose as examples of monosaccharides. Caption: Figure 1.1 Monosaccharide building blocks of polysaccharides “glucose fructose galactose structural formula OER diagram” 1.1.2 Types of linkages and branching Polysaccharides are formed through glycosidic linkages, which are covalent bonds between monosaccharide units. A glycosidic linkage is defined as the bond formed when the hydroxyl group of one sugar reacts with the anomeric carbon of another sugar. The most common linkages are alpha (α) and beta (β). Alpha linkages, such as α-1,4 and α-1,6, are found in starch and glycogen, giving them a branched and easily digestible structure. Beta linkages, such as β-1,4, are found in cellulose, making it rigid and resistant to digestion in humans. Branching occurs when additional linkages form at different positions, creating complex structures that influence solubility and biological function. Fill in the blank: The bond formed between monosaccharide units in polysaccharides is called a __________ linkage.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Short description: Diagram comparing α-1,4 glycosidic linkage in starch and β-1,4 linkage in cellulose. Caption: Figure 1.2 Types of glycosidic linkages in polysaccharides “alpha beta glycosidic linkage starch cellulose OER diagram” 1.1.3 Structural diversity among polysaccharides The structural diversity of polysaccharides arises from variations in monosaccharide composition, linkage types, and branching patterns. Homopolysaccharides are defined as polysaccharides composed of only one type of monosaccharide, such as starch (glucose units). Heteropolysaccharides contain more than one type of monosaccharide, such as hyaluronic acid. This diversity allows polysaccharides to perform a wide range of biological functions. For example, starch and glycogen act as energy storage molecules, while cellulose and chitin provide structural support. The complexity of branching also influences how enzymes interact with these molecules, determining their digestibility and metabolic roles. Fill in the blank: A polysaccharide composed of only one type of monosaccharide is called a __________.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Table 1.1 Examples of homopolysaccharides and heteropolysaccharides Table listing examples of homopolysaccharides (starch, glycogen, cellulose) and heteropolysaccharides (hyaluronic acid, chondroitin sulphate). “homopolysaccharides heteropolysaccharides examples OER table” Pilot questions 1.1 Which simple sugar molecules serve as the building blocks of polysaccharides? What type of bond connects monosaccharide units in polysaccharides? Differentiate between alpha and beta glycosidic linkages with examples. What is the difference between homopolysaccharides and heteropolysaccharides? How does branching influence the biological function of polysaccharides? 1.2 Functions and Biological Roles of Polysaccharides 1.2.1 Storage polysaccharides Storage polysaccharides are carbohydrate polymers that serve as energy reserves in living organisms. The most common examples are starch in plants and glycogen in animals. Starch is composed of amylose and amylopectin, which are glucose polymers linked mainly by α-1,4 bonds, with amylopectin containing additional α-1,6 branches. Glycogen is highly branched, allowing rapid mobilisation of glucose when energy is required. These storage molecules are crucial because they provide a compact and efficient way to store glucose, which can be released during metabolic processes such as glycolysis. Fill in the blank: The storage polysaccharide found in animals is called __________.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Diagram showing the structure of starch and glycogen, highlighting branching patterns. Figure 1.3 Storage polysaccharides: starch and glycogen “starch glycogen structure diagram OER” 1.2.2 Structural polysaccharides Structural polysaccharides provide rigidity and support to cells and tissues. The most notable examples are cellulose in plants and chitin in fungi and arthropods. Cellulose consists of β-1,4 linked glucose units, forming long straight chains that bundle into fibres, giving plants mechanical strength. Chitin is composed of N-acetylglucosamine units linked by β-1,4 bonds, forming a tough material found in insect exoskeletons and fungal cell walls. These polysaccharides are resistant to enzymatic digestion in humans, which explains why cellulose acts as dietary fibre rather than a source of energy. Fill in the blank: The structural polysaccharide found in plant cell walls is __________.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Image of plant cell walls and insect exoskeletons showing cellulose and chitin. Plate 1.1 Structural polysaccharides in nature “cellulose chitin plant cell wall insect exoskeleton OER image” 1.2.3 Specialised polysaccharides in biological systems Beyond storage and structural roles, some polysaccharides perform specialised functions. For example, glycosaminoglycans are long unbranched polysaccharides that play roles in connective tissues, joint lubrication, and cell signalling. Hyaluronic acid, a glycosaminoglycan, contributes to tissue hydration and elasticity. Other specialised polysaccharides include mucopolysaccharides, which form protective gels in mucus secretions. These polysaccharides highlight the versatility of carbohydrate polymers in biological systems, extending beyond energy storage and structural support to roles in communication, protection, and regulation. Fill in the blank: The glycosaminoglycan that contributes to tissue hydration and elasticity is __________ acid.
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