Enzymes 1

Enzymes 1

1. The chemical reactions requires for growth are anabolic (building up) reactions and are catalysed by enzymes. Catabolic reactions are breaking down reactions and are also catalysed by enzymes.

   • Enzymes can only increase the rates of reaction up to a certain point called the Vmax.

2. Hypotheses

   • Lock and key hypothesis
     • An area within the tertiary structure of the enzyme has a shape that Is complementary to the shape of a specific substrate molecule. This is called the active site.
       • When the substrate is bound to the active site an enzyme-substrate complex is formed. The substrate(s) then react and the product(s) are formed in an enzyme-product complex. The product(s) are then released. Leaving the enzyme unchanged.
         • The substrate is held in such a way by the enzyme that the right atom-groups are close enough to react. The R-groups within the active site of the enzyme will also interact with the substrate, forming temporary bonds. These put strain on the bonds within the substrate, which also helps the reaction along.
   • Induced-fit hypothesis
     • This suggests that the active site of the enzyme actually changes shape slightly as the substrate enters. The initial interaction between the enzyme and substrate is relatively weak, but these weak interactions rapidly induce changes in the enzymes tertiary structure that strengthen binding.
       • This puts a strain on the substrate molecule. This can weaken a particular bond or bonds in the substrate, therefore lowering the activation energy for the reaction.

3. Intracellular/extracellular enzymes

   • Intracellular - Enzymes that act within cells.
     • Extracellular - Enzymes that act out of cells.
       • Enzymes are released from cells to break down these large nutrient molecules into smaller molecules in the process of digestion.

4. Digestion of starch

   • Begins in mouth, continues in small intestine.
     • Amylase breaks it down in the saliva glands and pancreas.
       • It is then broken down by maltase which is present in the small intestine.

5. Digestion of proteins

   • Trypsin is a protease, a type of enzyme that catalyses the digestion of proteins into smaller peptides,which can then be broken down further into amino acids.
     • It is produced in the pancreas and released with pancreatic juice.