AQA A Level Biology复习笔记1.1.2 Biological Molecules: Reactions

Biological Molecules: Reactions

 

  • A covalent bond is the sharing of two or more electrons between two atoms
    • The electrons can be shared equally forming a nonpolar covalent bond or unequally (where an atom can be more electronegative δ-) to form a polar covalent bond

     

  • Generally each atom will form a certain number of covalent bonds due to the number of free electrons in the outer orbital e.g. H = 1 bond, C = 4 bonds
  • Covalent bonds are very stable as high energies are required to break the bonds
  • Multiple pairs of electrons can be shared forming double bonds (e.g. unsaturated fats C=C) or triple bonds

 

6-Covalent-bonds

 

Different types of covalent bonds

 

  • When two monomers are close enough that their outer orbitals overlap this results in their electrons being shared and a covalent bond forming. If more monomers are added then polymerisation occurs (and / or a macromolecule forms)

Condensation

  • Also known as dehydration synthesis (‘to put together while losing water’)
  • A condensation reaction occurs when monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules (lipids) and water is removed

 

6-Condensation-reaction

 

Written and symbolic illustrations of the removal of water to form a covalent bond between two or more monomers during a condensation reaction

 

Hydrolysis

  • Hydrolysis means ‘lyse’ (to break) and ‘hydro’ (with water)
  • In the hydrolysis of polymers, covalent bonds are broken when water is added

 

6-Hydrolysis-reaction

 

Written and symbolic illustrations of the addition of water to break down covalent bond/s during a hydrolysis reaction

 

Covalent Bonds in Organic Molecules Table

Covalent-bonds-in-organic-molecules-table

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