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Enzyme diagram (lipase):
E
S
ES-Complex
Here lipids are broken down by a lipase enzyme. The product of lipid hydrolysis is glycerol and fatty acids. In a practical, you would expect the pH of the solution to decrease as the reaction progresses.
Enzymes have an active site:
-The active site of the enzyme has a shape specific to its substrate.
-This specific shape is brought about due to the specific sequence of amino acids in the enzymes structure.
-The substrate forms chemical bonds with the active site, and the enzyme then undergoes a conformational change to better fit to the substrate.
-The enzyme-substrate complex has now been formed thanks to the complementary nature of the enzyme and substrate.
-The enzyme will now carry out its catalysis dependent on what enzyme it is (some break things down, other build things up)
Enzymes 'denature':
When an enzyme denatures, it loses its complementarity to its substrate. This occurs by the shape of the active site changing shape so that it can no loner bind its substrate. This will result in less ES complexes being formed, and therefore a lower rate of reaction.
Denaturation can be caused by:
-Changes in temperature (bond vibration)
-Changes in pH (ionic bonds/h-bonds)
-Non-competitive inhibition (allosteric)
Temperature explained:
-If the temperature is too low, the enzyme and substrate molecules have too low of an average kinetic energy (KE). This will mean there is a lower likelihood of frequent successful collisions and therefore less ES complexes are formed. Rate will therefore be lower.
-If the temperature is too high, the active site of the enzymes will denature and will not be able to bind the substrate (loss of complementarity) and therefore less ES complexes will form. Rate will therefore be lower.
*At freezing temperatures, ice crystals have the possibility of forming in the enzymes tertiary structure, disrupting the shape and causing the active site to denature.
Enzyme
Carbohydrase
Amylase
Lipase
Protease
Substrate
Carbohydrate
Starch
Fats/Lipids
Protein
Product
Simple sugars and glucose
Simple sugars and glucose
Fatty acids and glycerol
Amino acids
Competitive vs non-competitive inhibition:
-Competitive inhibitors have a similar shape to the substrate, and compete for the availability of the active site. This means less ES complexes form as the active sites of the enzymes are blocked by the inhibitor.
-Non-competitive inhibitors work by binding to a site other than the active site on an enzyme known as the allosteric site. They cause the active site to change shape by manipulating the enzymes shape from the allosteric site.
*Technically speaking, non-competitive inhibitors denature the active site of enzymes, preventing the substrate from binding as complementarity of shape is lost.
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