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Carbohydrates

carbohydrates - molecules w/ carbon, hydrogen, oxygen in ratio 1:2:1  

  • empirical formula - (CH2O)n
  • releases energy from C-H bonds when oxidized
  • sugars - most important energy-storage carbohydrate

monosaccharides - simplest of the carbohydrates  

  • can contain as few as 3 carbon, but most contain 6
  • C6H12O6, or (CH2O)6
  • usually forms rings in aqueous environments (but can form chains)
  • glucose - most important energy-storing monosaccaride; has 7 C-H bonds for energy

disaccharide - "double sugar"  

  • 2 monosaccharides joined by a covalent bond
  • play roles in transporting sugars (so that it is less rapidly used for energy during transport)
  • only special enzymes located at where glucose is to be used can break the bonds
  • normal enzymes along the transport route can't break apart disaccharides
  • sucrose - fructose + glucose; used by plants to transport glucose
  • lactose - galactose + glucose
  • maltose - glucose + glucose

polysaccharide - macromolecules made of monosaccharides  

  • insoluble long polymers of monosaccharides formed by dehydration synthesis
  • starch - used to store energy; consists of linked glucose molecules
  • cellulose - used for structural material in plants; consists of linked glucose molecules
  • amylose - simplest starch; all glucose connected in unbranched chains
  • amylopectin - plant starch; branches into amylose segments
  • glycogen - animal version of starch; has more branches than plant starch

sugar isomers - alternative forms of glucose  

  • same empirical formula, but different atomic arrangement
  • fructose - structural isomer of glucose; oxygen attached to internal carbon, not terminal; tastes sweeter than glucose
  • galactose - stereoisomer of glucose; hydroxyl group oriented differently from glucose

structural carbohydrates  

  • alpha form - where glucose bonds w/ the hydroxyl group below the plane of the ring
  • beta form - where the glucose bonds w/ the hydroxyl group above the plane of the ring
  • starch contains alpha-glucose chains
  • cellulose - contains beta-glucose chains; cannot be broken down by starch-degrading enzymes; serves as structural material
  • a few animals use bacteria/protists to break down cellulose
  • chitin - structural material in arthropods/fungi; modified cellulose w/ nitrogen group added to glucose units
Subject: 
Biology
Subject X2: 
Biology

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