AS Biology: Carbohydrates

Carbohydrates: what they are made up of, monomers, polymers + functions

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Made of Elements

  • Carbon
  • Hydrogen
  • Oxygen
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Structural formula of monomers

(http://www.fas.org/irp/imint/docs/rst/Sect20/glucrings1.GIF)

Monomers are any simple sugar e.g. glucose.

Alpha glucose has a hydrogen(H) above carbon-1, where as beta glucose has a hydroxide(OH) above the carbon-1.

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Joining monomers together- forming a polymer

(http://s3.hubimg.com/u/7628894_f520.jpg)

Two alpha glucose monomers join together in a condensation reaction, forming a glycosidic bond between O-C and releasing a molecule of H20.

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Different Forms

Monosaccharide:

  • Glucose
  • Fructose
  • Galactose

Disaccharides:

  • Sucrose = alpha glucose + fructose
  • Lactose = alpha glucose + galactose
  • Maltese = alpha glucose + alpha glucose

Polysaccharide:

  • Cellulose = beta glucose
  • Glycogen = alpha glucose
  • Starch = alpha glucose
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Functions

Starch:

  • Stores glucose in plants for respiration
  • Made from amylase(coiled for compact storage) and amylopectin(branched for ease of breakdown)
  • Insoluble - doesn't affect water potential

Glycogen:

  • Stores glucose in animals for respiration
  • Made of amylopectin
  • More branched than starch(so lots of energy can be easily be broken down)
  • Insoluble - doesn't affect water potential

Cellulose:

  • Cell structure/structural strength in plant cell walls - preventing lysis
  • Chain of beta glucose - alternate beta glucose rotated by 180 degrees
  • Able to form many hydrogen(H) bonds between OH groups
  • Produces microfibrils which bond together to form fibres at different angles(gives strength)
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