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How do enzymes speed up a reaction?
Enzymes are protein catalysts that accelerate a reaction by reducing the amount of activation energy required.
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(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.
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(T/F) Enzymes are very selective in the reactions they catalyze.
True.
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What is a substrate?
A substrate is a molecule upon which an enzyme acts.
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What is an active site?
An active site is the area of an enzyme to which a substrate binds.
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What is the lock and key theory?
The lock and key theory states that an enzyme and its corresponding active site are exactly complementary.
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(T/F) The induced fit hypothesis holds that an enzyme causes a conformational change in its corresponding active site to facilitate substrate binding.
True.
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What is a cofactor?
A cofactor is a nonprotein moleculte that is incorporated into an enzyme and is required for proper functioning.
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What is the difference between an apoenzyme and a holoenzyme?
An apoenzyme is an enzyme without its corresponding cofactor.
A holoenzyme contains its cofactor.
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What is a coenzyme?
A coenzyme is an organic cofactor for an enzymatic reaction (e.g.vitamin).
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What is a prosthetic group?
A tightly bound cofactor is also known as a prosthetic group.
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(T/F) Most coenzymes are synthesizd by the body.
False, most coenzymes are obtained from outside sources.
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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.
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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.
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(T/F) At very high concentrations of substrate, reaction rate approximates Vmax.
True.
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(T/F) All enzymes in the body are proteins.
False, ribozymes are RNA enzymes.
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What is the optimal pH for the enzymes of glycolysis?
7.
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What is the optimal tmeprature for most enzymes in the body?
37°C
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(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.
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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.
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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.
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What are the three categories of enzymatic regulatory inhibition?
Feedback, reversible, and irreversible inhibition.
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How does feedback inhibition regulate an enzymatic process?
Feedback inhibition uses an end product as an allosteric inhibitor to the enzyme catalyzing the reaction.
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What are the two types of reversible inhibitors?
The two types of reversible inhibitors are competitive and non-competitive inhibitors.
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(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.
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(T/F) A competitive inhibitor binds at the active site and therefore can be overcome by increasing the concentration of substrate.
True.
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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.
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(T/F) Irreversible inhibition involves permanent damage to the active site.
True.
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What is a zymogen?
A zymogen is an inactive form of an enzyme.
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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 pepsinogen and chymotrypsinogen. (note the "ogen" suffix).
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