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| Question | Answer |
| What are the 2 types of enzyme inhibitors? | Competitive inhibitor Non-competitive inhibitor |
| How do competitive inhibitors work? |
Competitive inhibitors have a similar shape to the substrates
They compete with substrates to bind to the active site but no reaction takes place; they block the active site
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| What happens to competitive inhibition when the concentration of substrates increases? |
The effect is reversed and the substrate will out-compete the inhibitors
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| How do non-competitive inhibitors work? |
Non-competitive inhibitors bind to the enzyme at the allosteric site.
This causes the active site to change shape so the substrate can no longer bind to it.
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| What happens to non-competitive inhibition when the concentration of substrates increases? |
Increasing the substrate concentration will have NO EFFECT.
This is because non-competitive inhibitors do not "compete" with the substrates as they have a different shape
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| Enzymes inhibitors can either be reversible or non-reversible. What does this depend on? | The strength of the bonds between the enzyme and the inhibitor |
| How do covalent bonds between the enzyme and inhibitor affect inhibition? | Strong covalent bonds = inhibitor cannot be easily removed and inhibition is irreversible |
| How do hydrogen/ionic bonds between the enzyme and inhibitor affect inhibition? | Weaker hydrogen/ionic bonds = inhibitor can be removed and inhibition is reversible |
| What is a metabolic pathway? | A series of connected metabolic reactions. Each reaction is catalysed by a different enzyme |
| How are metabolic pathways regulated? | By end-product inhibition - many enzymes are inhibited by the product of the reaction they catalyse |
| What is end-product inhibition? |
When the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway
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| Complete the sentences: End-product inhibition is ____________, so when the level of the end-product drops, _________drops and so more product can be made. This is a good way of ___________ the pathway and controlling the amount of ______-___________ that gets made. This is a ___________ ___________ mechanism. | End-product inhibition is REVERSIBLE, so when the level of the end-product drops, INHIBITION drops and so more product can be made. This is a good way of REGULATING the pathway and controlling the amount of END-PRODUCT that gets made. This is a NEGATIVE FEEDBACK mechanism. |
| What do metabolic poisons do? | Metabolic poisons interfere with metabolic reactions (reactions that occur in cells), causing damage, illness or death |
| Give examples of metabolic poisons | Cyanide = non-competitive, irreversible inhibitor of cytochrome c oxidase (enzyme that catalyses respiration) Arsenic = non-competitive inhibitor of pyruvate dehydrogenase (enzyme that catalyses respiration) Malonate = competitive inhibitor of succinate dehydrogenase (catalyses respiration) |
| TRUE OR FALSE: Some medicinal drugs are enzyme inhibitors | TRUE |
| Name examples of medicinal drugs which act as enzyme inhibitors | Aspirin ATPase inhibitors ACE inhibitors Protease inhibitors Nucleoside reverse transcriptase inhibitors |
| How does aspirin act as an enzyme inhibitor? | Aspirin binds to enzymes that catalyse the formation of prostaglandins |
| How do ATPase inhibitors act as enzyme inhibitors? | ATPase inhibitors inhibit sodium-potassium pumps in the cell membranes of heart-muscle cells, allowing more Ca²⁺ to enter cells (increases muscle contraction) |
| How do ACE inhibitors act as enzyme inhibitors? | ACE inhibitors inhibit angiotensin converting enzyme (ACE) to lower blood pressure and treat heart failure |
| How do protease inhibitors act as enzyme inhibitors? | Protease inhibitors are used to treat some viral infections. They prevent replication of the virus particles within host cells by inhibiting protease enzymes so viral coats cannot be made |
| How do nucleoside reverse transcriptase inhibitors act as enzyme inhibitors? | Nucleoside reverse transcriptase inhibitors are used to treat to treat HIV by inhibiting reverse transcriptase (catalyses replication of viral DNA) |
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