Enzymes Flashcards
U1L6b
What are Enzymes?
Enzymes are molecules that catalyze/speed up chemical reactions in biological systems by lowering their activation energy (eA).
What is Activation Energy?
Activation Energy is the amount of energy required to begin any reaction.
If the activation energy is large the reaction will proceed, but too slowly for biological systems
How do Enzymes affect the Activation Energy?
Enzymes essentially lower the energy barrier. The energy released is the same or without the catalyst (in this case enzymes), it just helps break it down faster.
What does an Enzyme look like?
Enzymes have an active site which is where the substrate goes on to. It could bind one or more substrate molecules which forces them into a transition state.
What are the different ways catalysts can cause substrates to enter a transition state?
1) Orientation: Brings substrates into correct position.
2) Physical Strain: Puts strain on chemical bonds making it weaker and easier to rearrange.
3) Chemical Charge: adds/removes ions to destabilize the substrate.
4) Induced Fit: Enzyme changes shape and induces a fit between enzyme and substrate, improving enzyme’s catalytic ability.
Why do Catalyzed reactions reach a maximum rate?
Because there is usually less enzyme than substrates present.
This causes the reaction rate to level off when all enzymes become saturated.
How is enzyme activity regulated?
Enzymes can be activated by co-factors/co-enzymes.
Enzymes can also be inhibited by inhibitors (reversible).
Inhibitors can be competitive or allosteric.
What’s the difference between Allosteric and competitive?
Allosteric or non-competitive, the inhibitor binds onto the allosteric site which essentially closes down the active site.
Competitive inhibitors, the inhibitor binds onto the active site, essentially blocking anything from reaching the active site.
Allosteric inhibitors are more efficient.
What effects enzyme activity?
1) pH effects activity:
Each enzyme catalyzes its reaction at a maximum
rate at a particular pH.
2) Temperature: Each enzyme is more active at a particular temperature. At higher temperatures, denaturation reduces the enzyme’s activity.
