Enzymes2 Flashcards
Who coined the term enzyme?
Frederick W. Kuhne
What is the origin of the term enzyme?
From Greek enzymos which means leavened
What enzyme was isolated for the first time and who did it?
Urease crystallized by James Sumner in 1926
Who crystallized and purified the enzyme trypsin, pepsin, and other digestive enzymes?
Northrop and Moses Kunitz
True or False? The primary, secondary, and tertiary structures of an enzyme are all crucial for it’s functionality?
Yes
What is co-factor?
Metal ions needed by enzymes
What is a coenzyme?
Complex molecules or metallo complex molecules needed by an enzyme.
What is a prosthetic group?
When either coenzyme or metals covalently or tightly bound to an enzyme it’s known as prosthetic group.
What is a holoenzyme?
Functionally active enzyme with it’s cofactors or coenzymes
What is an apoenzyme or apoprotein?
The protein part of a functional enzyme
When an enzyme reacts with its substrate does the pockets contain the solution?
No, most of the time it is sequestered from the solution.
Does enzyme changes the equilibrium state of a reaction?
No it doesn’t change it but instead increases the rate of the reaction. Equilibria in this sense means that the concentration of both reactants and products are same.
What is the energy state of the substrate and products?
Substrates have higher energy state than products at the ground state. Exergonic reaction
Why is the transition state not a reaction intermediate?
Because it is simply an event in which bond breakage, formation, etc. takes place.
Why is S or P formation equally likely in transition state?
Because transition state is the highest energy state where partial bonds exist and thus a molecule can easily get converted to product or revert back to substrate form.
What is a rate limiting step in enzymatic reaction.
The chemical step with the highest activation energy or transition state of highest free energy.
What is the importance of a rate limiting step?
Determines the overall rate of a reaction.
Is it compulsory to have one rate limiting step?
There could be equal activation energy steps or all reactions could be partially rate limiting.
What is the relationship between rate of reaction and substrate?
Direct
What is a second order reaction?
When two compounds are involved in a reaction.
What is the relationship between rate constant k and activation energy?
Inverse
How does enzyme lowers the activation energy?
Two explanations, Covalent interaction between the enzyme and the substrate. Much of this energy is lowered via non-covalent interactions
What is binding energy and what is its importance?
Free energy derived from non covalent interaction between substrate and enzyme. Reduces activation energy.
Why is a strictly complementary enzyme model not good?
Because in such model the enzyme is not flexible enough to facilitate interactions when the substrate is bending for instance the stick. Such model impedes the catalysis.
Where does the optimal interaction between substrate and enzyme takes place?
In the transition state
Why is a strictly complimentary model of enzyme not good in context of free energy?
If the enzyme is strictly complimentary to the substrate then the substrate has fewer interaction with the enzyme active site hence lower binding energy, which is the main source of lowering activation energy.
