Enzymes Flashcards
Enzymes
Biological catalysts made from proteins
What are biological catalysts
They speed up chemical reactions by decreasing activation energy
Lock and key hypothesis
Substrate fits enzyme active site perfectly
Induced fit model
the proximity of the substrate leads to a change in the enzyme that forms the functional active site. This distorts the bonds in the substrate and lowers the activation energy
No inhibitor
the substrate and enzyme fit together
Competitive inhibitor
have a molecular shape similar to the substrate allowing them to occupy the active site of an enzyme
Non- competitive inhibitor
attaches themselves to the enzyme at a binding site which changes the shape of the active site preventing enzyme substrate complex forming
Allosteric site
Where the inhibitor changes the shape of the enzyme in a non-competitive inhibitor
What make catalysts useful
They can be reused repeatedly and are therefore effective in small amounts
activation energy
the minimum amount of energy required to activate the reaction
how do enzymes work
They lower the activation energy which allows them the reaction to take place at a lower temperature
What structure do enzymes have
They have a specific 3-D structure (tertiary) that is the result of their sequence of amino acids.
What do a complimentary substrate and active site form
enzyme-substrate complex
What must happen for enzymes to work
- Come into physical contact with its substrate
-have an active site which fits the substrate
how are enzyme-catalysed reactions measured
measuring its time course
- the formation of the products of the reaction
-the disappearance of the substrate
What is the effect of temperature on enzyme action
A rise in temperature increase the kinetic energy of molecules which causes more collisions. More effective collisions means more enzyme substrate complexes. rate of reaction increases.
How can temperature lead to the denaturation of an enzyme
causes the bonds in the enzyme to break resulting in the enzyme to change shape and the substrate fits less easily, slowing the rate of reaction. The enzyme becomes so disrupted that it stops working altogether (denatured)
denaturation
permanent change to the active site causing the enzyme to stop functioning
What is the effect of pH on enzyme action
each enzyme has a optimum pH if the pH is changed from the optimum it will reduce the rate of reaction.if the change in pH is beyond a certain pH the enzyme becomes denatured.
how does pH affect the working of an enzyme
-A change in the pH alters the charge on the amino acids that make up the active site of the enzyme. Results in the substrate no longer being becoming attached to the active site- enzyme substrate complex can’t be formed
-depending on how significant the change in pH is, it may cause the bonds maintaining the enzymes tertiary structure to break and therefore the active site changes shape
What is the effect of enzyme concentration on the rate of reaction
enzymes being catalysts in a reaction they are not used up and therefore work effectively at very low concentrations.As long as there is an excess of substrate an increase in the amount of enzyme leads to proportionate increase in the rate of reaction.
what is the effect of substrate concentration on the rate of reaction
if the concentration of enzyme is fixed and substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate
What are enzyme inhibitors
substances that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity
What reduces the effect of a competitive inhibitor
increased substrate concentration
