2.1.4 - Enzymes Flashcards
(26 cards)
Describe feedback inhibition
When a product of a reaction acts as an inhibitor to the enzyme that produces it.
What type of mechanism is feedback inhibition
Negative feedback
What type of shape change occurs when a noncompetitive inhibitor binds to an enzyme
Conformational
What’s the site that NC inhibitors bind to
Allosteric
Site that competitive inhibitors bind to
Active site
Describe a graph comparing comp. inhibition with no inhibitor (rate against substrate concentration)
Rate of reaction reduced as inhibitor competes with substrate. Max rate can still be reached if substrate conc high enough
Describe a graph comparing non-comp. inhibition with no inhibitor (rate against substrate concentration)
Rate of reaction reduced as enzyme active site altered. Max rate can’t be reached by raising substrate conc
Lowers Vmax
Why is the first enzyme in a pathway more likely to be inhibited in feedback inhibition
Most energy efficient
Explain the term biological catalyst
Proteins used in metabolism that lower activation energy
Describe an enzyme graph of rate against temperature
Initially increases
At a certain temperature (optimum) the rate peaks
Rate decreases rapidly past this point
Rate stops at a certain temperature
Why can some inhibitors bind to active sites
They have a similar shape to that enzyme’s substrate molecule, so its shape is complimentary to the enzyme’s active site.
Describe a graph of rate against substrate concentration.
Increasing substrate conc increases the rate of reaction -> more substrate molecules entering active sites and forming ESCs
Vmax = all active sites occupied at highest concentration
Graph plateaus at Vmax and enzyme concentration is the limiting factor
Compare cofactor/coenzyme binding to prosthetic group binding
COFACTOR :
Temporary
Ionic / hydrogen bonds
PROSTHETIC GROUP :
Permanent
Covalent bonds
What are the differences between cofactors and coenzymes
COFACTORS:
- Derived from minerals in the diet (e.g. iron or calcium)
- inorganic
COENZYMES :
- derived from vitamins
- organic
What can some coenzymes do beyond just initiating conformational change?
Transfer important molecules to enzymes (e.g. protons and NAD+)
What are inactive precursor enzymes and why are they the way they are
Enzymes produced in an inactive form.
- > In some cases, to prevent damage within the cells that produce them or to the tissues where they are released.
- > Other cases, to control enzyme action and only have them be activated under certain conditions.
How are precursor enzymes activated
Addition of a cofactor/coenzyme, action of another enzyme, or a change in conditions (pH / temp) to initiate conformational change.
What’s a precursor enzyme called pre-cofactor?
Post-cofactor?
Apoenzyme
Holoenzyme
What are precursor enzymes called that undergo change in tertiary structure due to pH/temp conditions or other enzymes’ actions?
Zymogens or proenzymes
What may inactive proenzymes contain?
Extra amino acids to be removed by hydrolysis to reveal the active site by changing tertiary structure.
How do cofactors/coenzymes/prosthetic groups cause conformational change?
What benefit does this have?
By affecting the charges of the active site or the Hydrogen/Ionic bonds.
This increases the chances of the successful binding of a substrate and ESC formation.
Give an example of a cofactor
Chloride ions in amylase
Give two examples of a coenzyme
Vitamin B3 needed to make coenzyme NAD
Vitamins B5 needed to make coenzyme A
Give an example of a prosthetic group
Zinc ion forming part of the structure of carbonic anhydrase (aid carriage of CO2)
