Enzyme ​
Tags
Cegep1
Biology
Word count
248 words
Reading time
2 minutes
Biological catalyst
Protein or RNA
Hyper-specialized, unlike inorganic catalysts
Enzyme + substrates -> enzyme-substrate complex -> enzyme + products
[!abstract] Substrate
Substance on which an enzyme acts
[!abstract] Active site
Pocket or groove of an enzyme where the substrate binds via weak bonds such as H-bonds and ionic bonds
[!abstract] Induced fit
Change in the shape of an enzyme to fit the substrate
Mechanics ​
- Ensures substrates collide in the correct orientation
- Stresses bonds so that they break more easily
- Changes local environment to favour the reaction, e.g. different pH
- Active site side chains can participate directly in the reaction
Factors affecting reaction rate ​
- Temperature
- pH
- Enzyme concentration
- Cofactor concentration if required
- Substrate concentration
- Inhibitor type and concentration if present
Inhibition ​
[!abstract]+ Negative feedback inhibition
Mechanism where the final product inhibits one of its enzymes
Naturally maintains the amount of product at a certain level
Reversibility ​
- Irreversible: inhibitor attaches by a covalent bond
- Dangerous
[!example] Nerve gas, penicillin, some poisons
- Reversible: inhibitor attaches by a weak bond
- Important for regulating metabolism
[!example] ATP inhibits PFK, which slows down cellular respiration.
All biological inhibitors are reversible
Competitiveness ​
- Competitive: binds to the active site
- Competes with substrates => affected by substrate concentration
- Non-competitive: binds somewhere else on the enzyme, causing it to change shape
- Doesn't compete with substrates => unaffected by substrate concentration
Ajitani Hifumi