Proteins and Enzymes

• Proteins are made of long chains of small molecules

  called amino acids.
• Structural – usually long, thin and strong.
• Enzymes – 3D blobs (globular).
• Antibodies – Y shaped.
• Hormones act as messengers in the body e.g. insulin
• Hormones are carried in the blood to act on their

  target cells.
• Antibodies make up part of our immune system. They are produced by white blood cells.
• Antibodies bind on to pathogens and destroy them.
• Enzymes speed up the rate of reactions in

  cells. Substrates bind to the active site.
• Receptors are Y shaped molecules found on

  the surface of cells.
• Receptors have a specific shape which allows only

  certain molecules, such as hormones, to bind

  with them.
• Enzymes are biological catalysts and are

  made by all living cells– they speed up

  cellular reactions and are unchanged in the

  process.
• Substrate - The substance that an enzyme acts on
• Enzyme - The catalyst that speeds up the reaction
• Enzymes are very specific about which reactions they catalyse. Only molecules with exactly the right shape will bind to the enzyme and react. These are the reactant, or substrate, molecules.
• The part of the enzyme to which the substrate binds

  is called the active site. This is a very specific shape and the most important part of the enzyme. The

  shape of the active site of an enzyme molecule is

  complementary to its substrate(s).
• Degradation (breakdown) reaction - LARGE molecule to small molecules
• Synthesis (build up) reaction - Small molecules joined to make a large molecule
• Each enzyme is most active in its optimum

  condition. For example at a particular

  temperature or pH.
• Factors that affect the rate of a reaction include:

  
  

  -substrate

  concentration

  
  

  -temperature

  
  

  -pH

  
  

  -enzyme concentration

  
  

  -surface area