Biological Molecules

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Biological Molecules Intro

Living Things

80% of a living organism is water

13% is organic marcromolecukes

  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic acids

7% is non-organic molecules

  • Vitamins


  • Readily forms bonds with other carbons
  • Forms a backbone for other carbons to attach to
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Carbohydrates only contain: Carbon, Hydrogen and Oxygen.

Carbohydrates ------> Sugars -------> Monosaccharides {Glucose, Fructose, Galactose}

                                               --------> Disaccharides {Maltose, Sucrose, Lactose}

                         ------> Polysaccharides {Starch, Glycogen, Cellulose}

  • Disaccharides are formed when 2 monosaccharides join together
  • The reaction forms a water molecule so it is known as a condensation reaction
  • The type of bond formed is called a glycosidic bond
  • The opposite of a condensation reaction is a hydrolysis reaction

Maltose = Glucose + glucose

Lactose = Glucose + galactose

Sucrose = Glucose + fructose

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Forming Maltose

  • Two glucose molecules C1 and C4 meet
  • OH (Hydroxyl group) from C1 and H from C4 react
  • Water is expelled


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Polysaccharides (Starch)

Polysaccharides are polymers with subunits of monosaccharides They are NOT sugars


  • Plant Storage polysaccharides
  • Made up of amylase and amylopectin


  • Condensation reaction between alpha glucose forms 1000s of condensation reactions. 
  • Coiled springs are formed


  • Condensation reaction between Glucose 1-4 links
  • 1-6 branches also exist

A storage molecule needs to be big so that they are not soluble, they need to be coiled to fit lots in a small area.Storage structures are branched because it makes them stronger.

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Polysaccharides (Glycogen)

  • Storage polysaccharide in animals. Found in the liver and muscle cells where a store of energy is needed. Many fungi also store glycogen.
  • More branched than starch as animals need more energy - it is easier to break the glycogen apart when it is branched.
  • Forms tiny granules inside cells which are usually associated with the smooth endoplasmic reticulem.
  • Each glycogen contains a few thousand glucose links.

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Polysaccharides (Cellulose)

  • Cellulose is found in the cell wall of plants.
  • It is the most abundant organic molecule.
  • It is mechanically very strong.
  • It is a polymer of Beta glucose.
  • This structure has H bonds holding it together. They are relitavely weak.
  • If C1 and C4 are to react, 1 glucose has to flip 180 degrees.
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