Chapter 6 (6.5-6.7) Slides

• Disaccharides


  Consist of two monosaccharide units joined together
• A disaccharide can be split into two monosaccharide units
• Sucrose


  Ordinary table sugar, C12H22O11, is made of the two monosaccharides glucose and fructose
• Condensation and Hydrolysis


  Forming and Breaking Glycosidic Bonds
• Anomeric carbon


  In a monosaccharide in ring form, the anomeric carbon has the most reactive—OH in the molecule (C1 in an aldose)
• Glycoside formation


  1. When the hydroxyl on the anomeric carbon reacts with a hydroxyl on another monosaccharide, a glycoside is formed

  2. The bond that connects the two is a glycosidic bond

  3. Glycosidic bonds join monosaccharides to each other and connect monosaccharides to any alcohol
• α glycosidic bond


  If glycosidic bond is trans to carbon 6
• β glycosidic bond


  If glycosidic bond is cis to carbon 6
• Maltose


  • The glycosidic bond is specified as α(1→4)
• Cellobiose


  • The glycosidic bond is β(1→4)
• Three important disaccharides

  • Maltose
  • Lactose
  • Sucrose
• Maltose


  A disaccharide formed in the breakdown of starch, found in malted barley
• Lactose


  • Milk sugar, found in mammalian milk, the glycosidic bond is β(1→4) between C1 of β-galactose and C4 of glucose
  • Lactose intolerance occurs in people without lactase, causing undigested lactose to be broken down by intestinal bacteria, producing gas and cramping
• Sucrose


  The most abundant disaccharide in nature, found in sugar cane and sugar beets, formed by an α, β(1→2) glycosidic bond between glucose and fructose, with both anomeric carbons bonded so it is not a reducing sugar
• Glucose storage

  In plants: starch

  In animals: glycogen
• Glucose storage


  Connecting α-glucose units through glycosidic bonds
• Cellulose


  Structural material in plants, produced by connecting many β-glucose units
• Polysaccharides


  Large molecules consisting of 10 or more monosaccharide units bonded through their anomeric carbon atom
• Polysaccharides do not contain a sufficient number of reducing ends to give a positive Benedict's test
• Important polysaccharides

  • Starch
  • Glycogen
  • Cellulose
  • Chitin
• Starch


  A mixture of amylose (unbranched, linear spiral) and amylopectin (branched, globular)
• Digestion of starch


  Broken down into glucose units for use by the body
• Starch


  A "complex carbohydrate"
• Amylopectin


  • About one branch every 25 glucose units
• Glycogen


  The storage polysaccharide found in animals, mostly in the liver and muscles
• Glycogen


  • Very similar structure to amylopectin but the branching is different (about one branch every 12 glucose units)
• Glycogen synthesis and breakdown

  α-1,6 glycosidic bonds produced by non-regulatory branching enzyme (and broken by debranching enzyme)

  α-1,4 glycosidic bonds produced by regulatory glycogen synthase (and broken by glycogen phosphorylase)
• Cellulose


  Contains β(1→4)-bonded glucose units, altering the overall structure compared to amylose
• Chitin


  A polysaccharide that makes up the exoskeleton of insects and crustaceans and the cell walls of most fungi, made up of a modified β-D-glucose called N-acetylglucosamine with β(1→4) glycosidic bonds
• Red blood cells


  Have a number of chemical markers bonded to the cell surface
• Chemical markers on red blood cells

  • Include the A B O blood markers, which contain three or four monosaccharides
• Each person’s immune system can recognize only its own carbohydrate set (A, B, or O) and will try to destroy what it considers a foreign blood type
• 1. type blood

  No blood type recognizes the O carbohydrate set as foreign
• A B blood type


  Considered the universal acceptor blood type as A B blood contains all possible A B O combination types, so any blood type transfused will be accepted by the body
• Each person’s immune system

  Can recognize only its own carbohydrate set (A, B, or O) and will try to destroy what it considers a foreign blood type
• Trisaccharide on the cells of O-type blood


  Present on cells of all blood types (A, B, and A B)
• AB blood type


  Considered the universal acceptor blood type as it contains all possible A B O combination types, so any blood type transfused will be accepted by the body