Enzymes At Work (2.1.3)

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What is an enzyme inhibitor?
Any substance or molecule that slows down the rate of an enzyme catalysed reaction by affecting the enzyme molecule.
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What are competitive inhibitors?
They have a similar shape to the substrate and can occupy the enzyme active site to give an enzyme-inhibitor complex. This prevents the enzyme joining with the substrate to catalyse the usual reaction.
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How can the effect of competitive inhibitors be overcome?
Increasing the concentration of the substrate as this is reversible.
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What are non-competitive inhibitors?
They don't compete with the substrate molecule for the enzyme active site. Instead, they attach to the enzyme somewhere other than the active site.
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How do non-competitive inhibitors affect enzyme activity?
They can distort the tertiary structure and specific shape of the enzyme active site. The substrate may no longer fit into it, meaning fewer ES complexes per second.
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Are the effects of non-competitive inhibitors reversible?
They are irreversible. Once the inhibitor has joined to the enzyme, the enzyme is permanently denatured.
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What will happen if the concentration of substrates is increased to combat the effect of the non-competitive inhibitors?
Changing the concentration of the substrate will have no effect.
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What are the three types of enzyme co-factors?
Co-enzymes, prosthetic groups and inorganic ion co-factors.
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What is a co-factor?
A non-protein substance that helps a reaction to be catalysted.
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What do co-enzymes do?
Small, organic non-protein molecule. Binds for short period to active site, just before or at same time as substrate. Takes part in reaction & changed in some way- recycled afterwards. Can carry chemical groups between enzymes to link reactions.
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What do prosthetic groups do?
A prosthetic group is a co-enzyme that is permanently attached to an enzyme. They contribute to the specific 3D shape and charge of the enzyme molecule. They are necessary to ensure that the substrate can fit into the active site.
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What do inorganic ion co-factors do?
In some reactions, the presence of some ions can increase the reaction rate. These ions may combine with the enzyme or the substrate, making the ES complex more easy to form. They do this by affecting the distribution of charge.
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Give an example of a co-enzyme.
Vitamin B3 is a co-enzyme that helps us to release energy during the respiration of carbohydrates and lipids.
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Card 2

Front

What are competitive inhibitors?

Back

They have a similar shape to the substrate and can occupy the enzyme active site to give an enzyme-inhibitor complex. This prevents the enzyme joining with the substrate to catalyse the usual reaction.

Card 3

Front

How can the effect of competitive inhibitors be overcome?

Back

Preview of the front of card 3

Card 4

Front

What are non-competitive inhibitors?

Back

Preview of the front of card 4

Card 5

Front

How do non-competitive inhibitors affect enzyme activity?

Back

Preview of the front of card 5
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