saccharides

• Hydroxy Carbonyl Compounds:

  • Compounds that contain both a hydroxyl group (-OH) and a carbonyl group (C=O) in their structure
  • Characteristic functional groups of saccharides
• Polyhydroxy Aldehydes and Ketones:

  • Saccharides are often referred to as polyhydroxy aldehydes or ketones
  • Consist of multiple hydroxyl (-OH) groups attached to carbon atoms that are part of either an aldehyde (if the saccharide is an aldose) or a ketone (if the saccharide is a ketose) functional group
• Polybasic Alcohols and Their Polycondensates:

  • Saccharides are termed as polybasic alcohols due to containing multiple hydroxyl (-OH) groups
  • Polycondensates are formed through condensation reactions where multiple saccharide molecules join together
  • Joining typically occurs through glycosidic linkages to form larger carbohydrate polymers like disaccharides and polysaccharides
• Structural Isomerism:

  • Saccharides can have the same molecular formula but different structural arrangements of atoms
  • Examples include glucose, galactose, and fructose
• Stereoisomerism:

  • Saccharides can have the same molecular formula and structural arrangement but differ in spatial orientation
  • Leads to different stereoisomers like enantiomers and diastereomers
• Optical Isomerism:

  • Stereoisomers that are mirror images of each other and cannot be superimposed exhibit optical isomerism
  • Examples include D-glucose and L-glucose
• D/L-Isomerism:

  • Classification of stereoisomers based on their optical activity
  • L-isomers rotate plane-polarized light counterclockwise, while D-isomers rotate it clockwise
• Epimerism:

  • Diastereomers that differ in configuration at only one chiral center are called epimers
  • Examples include glucose and galactose
• Anomerism:

  • Anomers are cyclic saccharides that differ in configuration at the anomeric carbon
  • Typically in equilibrium between alpha and beta forms
• Fischer Projection and Tollens Projection:

  • Methods to represent the three-dimensional structure of saccharides on a two-dimensional plane
  • Fischer projection shows the molecule vertically, Tollens projection shows it horizontally
• Racemate:

  • A mixture containing equal amounts of both enantiomers
  • Optically inactive due to cancellation of optical rotation
• Hemiacetal and Hemiketal:

  • Functional groups formed by the reaction between an aldehyde or ketone group with an alcohol group during cyclic saccharide formation
• Anomeric Carbon:

  • In cyclic saccharides, the carbon atom derived from the carbonyl group becomes a stereocenter known as the anomeric carbon
  • Determines the alpha or beta configuration in anomers
• 1. Aldoses: Monosaccharides that contain an aldehyde functional group (-CHO) are called aldoses. Examples include glyceraldehyde, ribose, and glucose.
  2. Ketoses: Monosaccharides that contain a ketone functional group (C=O) are called ketoses. Examples include dihydroxyacetone, erythrose, and fructose.

   

  Chemical structure of saccharides= (CH2O)n n=>3
• Reactivity of Saccharides: Saccharides can undergo various chemical reactions due to the presence of functional groups like hydroxyl (-OH) and carbonyl (C=O) groups. These reactions include esterification, oxidation, reduction, and glycosidic bond formation.
• Esterification: Esterification is the chemical reaction between a saccharide and an alcohol in the presence of an acid catalyst, resulting in the formation of an ester and water. This reaction is commonly used in the synthesis of sugar esters for various applications.
• Generation of Oximes: Oximes are compounds formed by the reaction of saccharides with hydroxylamine under acidic conditions. This reaction is often used in carbohydrate chemistry to introduce functional groups for further modification.
• Generation of Hydrazones/Osazones: Saccharides can react with hydrazine or phenylhydrazine to form hydrazones or osazones, respectively. These reactions are useful for the identification and characterization of saccharides.
• Aldonic Acid: Aldonic acids are oxidized forms of aldoses, where the aldehyde group is oxidized to a carboxylic acid group. This reaction is commonly used in the Benedict's test for reducing sugars.
• Uronic Acid: Uronic acids are derived from aldoses through oxidation of the terminal hydroxyl group to a carboxylic acid group. They are common constituents of polysaccharides like pectin and hyaluronic acid.
• Aldaric Acid: Aldaric acids are produced by the oxidation of both terminal hydroxyl groups of a saccharide to carboxylic acid groups. They are used in the synthesis of sugar acids and as chelating agents.
• Glycosides: Glycosides are compounds formed by the condensation reaction between a saccharide and another molecule, typically an alcohol or phenol, resulting in the formation of a glycosidic bond. They are common natural products found in plants and microorganisms.
• Homo- or Heteroglycosides: Glycosides can be classified as either homoglycosides, where the aglycone (non-saccharide) part is another saccharide, or heteroglycosides, where the aglycone part is a non-saccharide compound.
• Glycoside Bonds: Glycoside bonds are covalent bonds formed between the anomeric carbon of a saccharide and a hydroxyl group of another molecule. They can be O-glycosidic bonds (between the anomeric carbon and an oxygen atom), S-glycosidic bonds (between the anomeric carbon and a sulfur atom), or N-glycosidic bonds (between the anomeric carbon and a nitrogen atom).
• Saccharides as Non-Electrolytes: Saccharides typically do not dissociate into ions when dissolved in water and therefore do not conduct electricity, making them non-electrolytes
• Generally Crystalline Solids, Soluble in Water: Saccharides are often crystalline solids at room temperature and are soluble in water due to their ability to form hydrogen bonds with water molecules.
• Derivatives of Saccharides: Various derivatives of saccharides exist, including sugar alcohols (e.g., sorbitol), sugar acids (e.g., glucuronic acid), and sugar phosphates (e.g., glucose-6-phosphate), which have different chemical properties and biological roles.
• Deoxy Saccharides: Deoxy saccharides are saccharides in which one or more hydroxyl groups are replaced by hydrogen atoms. Examples include deoxyribose, a component of DNA.
• Amino Saccharides: Amino saccharides are saccharides that contain an amino group (-NH2) in addition to hydroxyl groups. Glucosamine and galactosamine are common examples found in glycosaminoglycans and glycoproteins.
• 1. Source of Energy: Saccharides, particularly monosaccharides like glucose, serve as a primary source of energy for cells. They undergo cellular respiration to produce ATP, the universal energy currency of cells
• 1. Structural Function: Saccharides play a crucial role in providing structural support to cells and tissues. Polysaccharides like cellulose, chitin, and glycogen form structural components in plant cell walls, exoskeletons of arthropods, and energy storage granules in animals, respectively
• Part of Nucleic Acids: Saccharides are essential components of nucleic acids (DNA and RNA), where they form the backbone of the nucleic acid molecule. The sugar component of DNA is deoxyribose, while RNA contains ribose
• Glycogenic or Gluconeogenic: Saccharides can be either glycogenic or gluconeogenic, depending on their ability to be converted into glucose. Glycogenic saccharides, such as starch and glycogen, serve as storage forms of glucose and can be broken down to release glucose when needed for energy. Gluconeogenic saccharides, like certain amino acids and glycerol, can be converted into glucose during gluconeogenesis to maintain blood glucose levels
• Precursors for Biosynthesis: Saccharides serve as precursors for the biosynthesis of lipids and proteins. For example, glucose can be used in the synthesis of fatty acids and glycerol for lipid synthesis, while certain amino sugars are incorporated into glycoproteins
• Part of Nucleotides and Coenzymes: Saccharides are components of nucleotides, the building blocks of nucleic acids, where they form part of the sugar-phosphate backbone. Additionally, saccharides are involved in the synthesis of coenzymes like NAD+ and FAD, which play essential roles in cellular metabolism
• Intra and Inter-Cell Signaling: Saccharides participate in intra- and inter-cellular signaling processes. Cell surface saccharides, such as glycoproteins and glycolipids, are involved in cell recognition, adhesion, and communication. Additionally, saccharides can act as signaling molecules themselves, regulating various cellular processes
• Homo- and Heteropolysaccharides: Polysaccharides can be classified as homopolysaccharides if they are composed of only one type of monosaccharide unit (e.g., cellulose) or heteropolysaccharides if they contain two or more different monosaccharide units (e.g., glycosaminoglycans).
• 1. Glycoconjugates: Carbohydrates covalently linked to proteins (glycoproteins), lipids (glycolipids), or other molecules. They play essential roles in cell-cell recognition, signaling, and immunity.
• name structures:

  A) Pyranose

  B) Furanose

  C) Pyran

  D) Furan

  
• Peptidoglycans:

  • Peptidoglycans are complex molecules found in the cell walls of bacteria, providing structural support and protection.
  • They consist of long chains of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) residues, cross-linked by short peptide chains.
  • Peptidoglycans give bacterial cell walls their rigidity and help them withstand osmotic pressure changes.