Biology Flashcards - Enzymes
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Biology Flashcards - Enzymes
Biology Flashcards Enzymes
Biology Flashcards - Enzymes Kaplan MCAT B25-B34
How do enzymes speed up a reaction?
Enzymes are protein catalysts that accelerate a reaction by reducing the amount of activation energy required.
(T/F) Enzymes get used up during the course of a reaction.
False, enzymes are catalysts and therefore don't get used up during the course of a reaction.
(T/F) Enzymes are very selective in the reactions they catalyze.
What is a substrate?
A substrate is a molecule upon which an enzyme acts.
What is an active site?
An active site is the area of an enzyme to which a substrate binds.
What is the lock and key theory?
The lock and key theory states that an enzyme and its corresponding active site are exactly complementary.
(T/F) The induced fit hypothesis holds that an enzyme causes a conformational change in its corresponding active site to facilitate substrate binding.
What is a cofactor?
A cofactor is a nonprotein moleculte that is incorporated into an enzyme and is required for proper functioning.
What is the difference between an apoenzyme and a holoenzyme?
An apoenzyme is an enzyme without its corresponding cofactor.
A holoenzyme contains its cofactor.
What is a coenzyme?
A coenzyme is an organic cofactor for an enzymatic reaction (e.g.vitamin).
What is a prosthetic group?
A tightly bound cofactor is also known as a prosthetic group.
(T/F) Most coenzymes are synthesizd by the body.
False, most coenzymes are obtained from outside sources.
What happens to the free energy (
G) of a reaction if it is catalyzed by an enzyme?
The free energy of an enzyme-catalyzed reaction is the same as the reaction without the enzyme.
What happens as the concentration of substrate is increased in an enzyme-catalyzed reaction?
The reaction rate increases until most of the active sites are filled and then the reaction rate reaches a plateau.
(T/F) At very high concentrations of substrate, reaction rate approximates V
(T/F) All enzymes in the body are proteins.
False, ribozymes are RNA enzymes.
What is the optimal pH for the enzymes of glycolysis?
What is the optimal tmeprature for most enzymes in the body?
(T/F) All enzymes in the body operate most efficiently at a pH of around 7.2.
False, enzymes in the digestive tract work best at acidic and basic pH's.
What is an allosteric enzyme?
An allosteric enzyme is an enzyme with two or more active sites. An allosteric enzyme oscillates between an active and inactive configuration.
What happens to an enzyme in the presence of an allosteric inhibitor?
An allosteric inhibitor prevents an enzyme from binding to its substrate by stabilizing the inactive configuration.
What are the three categories of enzymatic regulatory inhibition?
Feedback, reversible, and irreversible inhibition.
How does feedback inhibition regulate an enzymatic process?
Feedback inhibition uses an end product as an allosteric inhibitor to the enzyme catalyzing the reaction.
What are the two types of reversible inhibitors?
The two types of reversible inhibitors are competitive and non-competitive inhibitors.
(T/F) A non-competitive inhibitor can be overcome by increasing the concentration of substrate.
False, a non-competitive inhibitor doesn't bind at the active site and therefore doesn't compete with the substrate.
(T/F) A competitive inhibitor binds at the active site and therefore can be overcome by increasing the concentration of substrate.
How can a non-competitive inhibitor's effect e reversed?
Through the addition of a compound having a greater affinity for the inhibitor than the inhibitor has for the enzyme.
(T/F) Irreversible inhibition involves permanent damage to the active site.
What is a zymogen?
A zymogen is an inactive form of an enzyme.
How is a zymogen activated? Give some examples of zymogens.
A zymogen is activated when a part of it is cleaved off.
A few examples are digestive enzymes such as
. (note the "ogen" suffix).