BioChem - Carbohydrates

Cards (92)

  • Carbohydrates are composed of C, H, O
  • Functions of carbohydrates
    • Energy
    • Energy storage
    • Raw materials
    • Structural
  • Examples of carbohydrates
    • Sugars
    • Starches
    • Cellulose
  • Most of the matter in plants, except water, is carbohydrate material
  • Carbohydrates account for 75% of dry plant material and are produced by photosynthesis
  • Cellulose
    Structural element
  • Starch/glycogen
    Energy reservoir
  • Photosynthesis
    Plants produce carbohydrates using carbon dioxide, water, and solar energy
  • Carbohydrate oxidation provides energy
  • Carbohydrate storage, in the form of glycogen, provides a short-term energy reserve
  • Carbohydrates supply carbon atoms for the synthesis of other biochemical substances (proteins, lipids, and nucleic acids)
  • Carbohydrates form part of the structural framework of DNA and RNA molecules
  • Carbohydrates linked to lipids are structural components of cell membranes
  • Carbohydrates linked to proteins function in a variety of cell–cell and cell–molecule recognition processes
  • Empirical formula of simple carbohydrates
    CnH2nOn or Cn(H2O)n (hydrate of C)
  • Carbohydrate
    Polyhydroxy aldehyde, ketone, or a compound that produces such substances upon hydrolysis
  • Functional groups
    Carbonyl<|>Ketone<|>Aldehyde
  • Types of carbohydrates
    • Monosaccharide
    • Disaccharide
    • Polysaccharide
  • Monosaccharides
    Contain single polyhydroxy aldehyde or ketone unit<|>Cannot be broken down into simpler substances by hydrolysis reactions<|>Contain 3–7 C atoms<|>5 and 6 carbon species are more common<|>Pure monosaccharides - Water soluble white, crystalline solids
  • Disaccharides
    Contain 2 monosaccharide units covalently bonded to each other<|>Crystalline and water soluble substances
  • Common disaccharides
    • Table sugar (sucrose)
    • Milk sugar (lactose)
  • Oligosaccharides
    Contain three to ten monosaccharide units covalently bonded to each other<|>Usually found associated with proteins and lipids in complex molecules<|>Serve structural and regulatory functions
  • Polysaccharides
    Contain many monosaccharide units covalently bonded<|>Number of monosaccharide units varies from a few 100 units to 50,000 units
  • Examples of polysaccharides
    • Cellulose - Paper, cotton, wood
    • Starch - Bread, pasta, potatoes, rice, corn, beans, and peas
  • Chirality
    Chiral center: C atom attached to 4 different groups<|>A C atom must have four different groups attached to it in order to be a chiral center<|>Almost all monosaccharides are right handed<|>Amino acids are always left handed
  • Right- and left-handed baseball players cannot use the same glove (chiral) but can use the same hat (achiral)
  • Enantiomeric pairs have same solubility in achiral solvents like ethanol and have different solubility in chiral solvent like D-2-butanol
  • Classification of monosaccharides by number of carbon atoms
    • Triose - 3 carbon atoms
    • Tetrose - 4 carbon atoms
    • Pentoses - 5 carbon atoms
    • Hexoses - 6 carbon atoms
  • Classification of monosaccharides by functional groups
    • Aldoses: Monosaccharides with one aldehyde group
    • Ketoses: Monosaccharides with one ketone group
  • Aldohexose
    Monosaccharide with aldehyde group and 6 C atoms
  • Ketopentose
    Monosaccharide with ketone group and 5 C atoms
    1. Glucose
    Most abundant in nature<|>Most important source of human nutrition<|>Six-membered cyclic form
    1. Galactose
    Milk sugar<|>Synthesized in human beings<|>Part of brain and nerve tissue<|>Used to differentiate between blood types<|>Six-membered cyclic form
    1. Fructose
    Ketohexose<|>Sweetest tasting of all sugars<|>Found in many fruits and in honey<|>Good dietary sugar due to higher sweetness<|>Five-membered cyclic form
    1. Ribose
    Part of a variety of complex molecules which include RNA, ATP, and DNA<|>Five-membered cyclic form
  • Cyclic forms of D-Glucose
    α-form where the –OH of C1 and CH2OH of C5 are on opposite sides<|>β-form where the –OH of C1 and CH2OH of C5 are on the same side
  • Glycosidic linkage
    Formed when two monosaccharides react to form a disaccharide
  • Maltose (Malt Sugar)

    Structurally made of 2 D-glucose units, one of which must be α-D-glucose, linked via an α(1→4) glycosidic linkage<|>Digested easily by humans because of an enzyme that can break α(1→4) linkages
  • Cellobiose
    Produced as an intermediate in the hydrolysis of the polysaccharide cellulose<|>Contains two D-glucose monosaccharide units, one of which must have a β configuration, linked through a β(1→4) glycosidic linkage<|>Cannot be digested by humans
  • Lactose
    Made up of β-D-galactose unit and a D-glucose unit joined by a β(1→4) glycosidic linkage<|>Milk is rich in the disaccharide lactose<|>Lactase hydrolyzes β(1→4) glycosidic linkages