2.3 Enzymes Flashcards
What are enzymes?
Biological catalysts
What is the now rejected hypothesis for how enzymes work?
the lock and key hypothesis
What is the recently accepted hypothesis for the mechanism of enzyme action?
The induced fit model
What are intracellular enzymes and name an example?
enzymes that act within cells e.g. catalase
What are extracellular enzymes and name an example?
enzymes that are released from cells to break down large nutrients outside the cell e.g. amylase and trypsin
What are the 2 enzymes involved in the digestion of starch?
- amylase
- maltase
What enzyme is involved in the digestion of proteins?
trypsin
What are the factors that affect enzyme activity?
- temperature
- pH
- substrate concentration
- enzyme concentration
What is the temperature coefficient (Q10)?
a measure of how much the rate of reaction increases with a 10 degrees C rise in temperature
Why do enzymes denature at high temperatures?
the bonds holding the protein together vibrate more which causes the bonds to strain and break which changes the shape of the tertiary structure and the active site is no longer complementary to the substrate
What is the optimum temperature?
the temperature at which the enzyme has the highest rate of activity
Why does a change in pH denature enzymes?
A change in [H+] alters the active site, causing the enzyme to denature
What is renaturation?
If the pH does not change too drastically from the optimum and then returns to the optimum the protein can resume its normal shape
How does [substrate] affect the rate of an enzyme controlled reaction?
when [substrate] is increased the number of substrate molecules, atoms or ions in a particular volume increases which leads to a higher collision rate with the active site and thus formation of more enzyme-substrate complexes
How does [enzyme] affect the rate of an enzyme controlled reaction?
The number of available active sites increases leading to the formation of more enzyme-substrate complexes
What is competitive inhibition?
a molecule/part of a molecule has a similar shape to the substrate and can bind to the active site, preventing the substrate from doing so
Name 2 examples of competitive inhibitors
- statins
- aspirin
What is non-competitive inhibition?
The inhibitor binds at an allosteric site which changes the shape of the enzyme so the substrate can no longer bind.
Name 2 examples of non-competitive inhibitors
- organophosphates used as insecticides
- Proton pump inhibitors
What is end-product inhibition?
enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the product of a reaction e.g. ATP
What is the difference between cofactors and coenzymes?
Cofactors are a non-protein component that help enzymes carry out their function. Coenzymes are cofactors that are organic molecules.
What is the difference between a prosthetic group and a cofactor?
Prosthetic groups are tightly bound and form a permanent feature of the protein.
What is precursor activation?
A cofactor is added to an apoenzyme which activates it forming a holoenzyme
What does precursor activation do?
Changes the tertiary structure of the enzyme
What is an example of precursor activation?
when inactive pepsinogen the pH transforms it into active pepsin
