carbohydrates

• Macromolecules or polymers

  Large forms of organic compounds
• Four major classes of biological molecules

  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
• Carbohydrates constitute about 60-90% of the dry biomass in plants
• Polysaccharides


  • Polymers of simple sugars (monosaccharides)
• Hydrocarbons

  • Diesel
  • Petrol
  • Paraffin
  • Propane
• Classes of monosaccharides

  • Trioses
  • Tetroses
  • Pentoses
  • Hexoses
• Classification of Carbohydrates

  • Monosaccharides
  • Disaccharides
  • Oligosaccharides
  • Polysaccharides
• Energy in living organisms is stored in the form of carbohydrates
• Hydrocarbons

  Molecules consisting of carbon and hydrogen only
• Carbohydrates polymers

  • Starch
  • Cellulose
  • Glycogen
• Organic compounds

  Based on the chemistry of carbon which forms the framework of all biological molecules
• Classification of monosaccharides

  • Aldoses
  • Ketoses
• The most important energy-storage molecules are in the form of sugars
• Monosaccharides

  Small molecules that cannot be hydrolysed or broken down into simpler compounds by action of acids
• Types of monosaccharides

  • Arabinose
  • Deoxyribose
  • Ribose
  • Fructose
  • Glucose
  • Galactose
  • Mannose
• Triose sugar

  • glyceraldehyde
• Erythrose

  Occurs in all living organisms, particularly found in human blood and cartilage tissues
• Tetroses

  Monosaccharides with a chain of four carbon atoms
• Pentose sugars

  • ribose, deoxyribose
• Monosaccharides are described by the formula (CH2O)n, giving a ratio of 1:2:1 for C:H:O, explaining the term "carbohydrates" as "carbon with water added"
• Hexoses

  Monosaccharides with six carbon atoms
• Glucose

  Main metabolic fuel for mammals, transported through circulatory systems, main metabolic fuel for animal tissues
• Pentoses

  Monosaccharides with a chain of five carbon atoms
• Glyceraldehyde

  The simplest of the common aldoses, used in nutrition
• Tetrose sugar


  • erythrose
• Ribose and Deoxyribose

  Ribose found in RNA, deoxyribose found in DNA
• Trioses

  Monosaccharides with a chain of three carbon atoms
• Glucose is a constituent of many polysaccharides such as starch in plants and glycogen in animals, important in energy metabolism as a source of energy
• Glucose in clinical cases

  Excreted in large amounts in urine in cases like diabetes due to lack of insulin
• Hexose sugars

  • Glucose, Fructose
• Glucose is important in energy metabolism of animals as a source of energy
• Fructose

  A simple hexose sugar, a component of sucrose, a ketohexose, found in green plants, fruits, and honey, tastes sweeter than sucrose, used in soft drinks, canned fruits, and jam
• Disaccharides

  • Sucrose
  • Lactose
  • Maltose
• Hypoglycaemia is characterised by a deficiency of glucose in the bloodstream, leading to muscular weakness, dizziness, mental confusion, and sweating
• Disaccharides

  • Sucrose, lactose, maltose
• Synthesis of a disaccharide

  Fusion of two monosaccharides accompanied by loss of one molecule of water, known as dehydration synthesis or condensation reaction
• In sugar-cane plants, sucrose accumulates in the stems; in beetroot plants, sucrose accumulates in modified root tubers, sources of sugar in tropical regions and Europe respectively
• Maltose

  Disaccharide containing two molecules of glucose, occurs in high concentrations in germinating seeds of cereal plants, product of starch hydrolysis facilitated by amylase enzyme, structure illustrated in Figure 8
• Lactose

  Disaccharide composed of galactose and glucose, found in milk, less sweet than sucrose, structure illustrated in Figure 7
• Hydrolysis of sucrose

  Produces glucose and fructose