MCAT Biology - Enzymes
1. What is a coenzyme? 2. What is a prosthetic group? 3. (T/F) Most coenzymes are synthesized by the body
1. A coenzyme is an organic cofactor for an enzymatic reaction 2. A tightly bound cofactor is also known as a prosthetic group 3. False, most coenzymes are obtained from outside sources
1. What is a substrate? 2. What is an active site? 3. What is the lock and key theory?
1. A substrate is a molecule upon which an enzyme acts 2. An active site is the area of an enzyme to which a substrate binds 3. The lock and key theory states that an enzyme and its corresponding active site are exactly complementary
1. How do enzymes speed up a reaction? 2. (T/F) Enzymes get used up during the course of a reaction 3. (T/F) Enzymes are very selective in the reactions they catalyze
1. Enzymes are protein catalysts that accelerate a reaction by a reducing the amount of activation energy required 2. False, enzymes are catalysts and therefore don't get used up during the course of a reaction 3. True
1. (T/F) A non-competitive inhibitor can be overcome by increasing the concentration substrate 2. (T/F) A competitive inhibitor binds at the active site and therefore can be overcome by increasing the concentration of substrate 3. How can a non-competitive inhibitor's effect be reversed?
1. False, a non-competitive inhibitor doesn't bind at the active site and therefore doesn't compete with the substrate 2. True, a competitive inhibitor competes with the substrate for active sites 3. Through the addition of a compound having a greater affinity for the inhibitor than the inhibitor has for the enzyme
1. (T/F) All enzymes in the body operate most efficiently at a pH of around 7.2 2. What is an allosteric enzyme? 3. What happens to an enzyme in the presence of an allosteric inhibitor?
1. False, enzymes in the digestive tract work best at acidic and basic pH's 2. An allosteric enzyme is an enzyme with 2 or more active sites. An allosteric enzyme oscillates between an active and inactive configuration 3. An allosteric inhibitor prevents and enzyme from binding to its substrate by stabilizing the inactive configuration
1. (T/F) All enzymes in the body are proteins 2. What is the optimal pH of the enzymes of glycolysis? 3. What is the optimal temperature for most enzymes in the body?
1. False, ribozymes are RNA enzymes 2. 7 3. 37 degrees C
1. What are the 3 categories of enzymatic regulatory inhibition? 2. How does feedback inhibition regulate and enzymatic process? 3. What are the 2 types of reversible inhibitors?
1. Feedback, reversible, and irreversible inhibition 2. Feedback inhibition uses an end product as an allosteric inhibitor to the enzyme catalyzing the reaction 3. The 2 types of reversible inhibitors are competitive and non-competitive inhibitors
1. What happens to the free energy (delta G) of a reaction if it is catalyzed by an enzyme? 2. What happens as the concentration of substrate is increased in an enzyme-catalyzed reaction? 3. (T/F) At very high concentrations of substrate, reaction rate approximates Vmax
1. The free energy of an enzyme-catalyzed reaction is the same as the reaction without the enzyme 2. The reaction rate increases until most of the active sites are filled and then the reaction rate reaches a plateau 3. True
1. (T/F) The induced fit hypothesis holds that an enzyme causes a conformational change in its corresponding active site to facilitate substrate binding 2. What is a cofactor? 3. What is the difference between and apoenzyme and a holoenzyme?
1. True 2. A cofactor is a nonprotein molecule that is incorporated into an enzyme and is required for proper functioning 3. An apoenzyme is an enzyme without its corresponding cofactor. A holoenzyme contains its cofactor
1. (T/F) Irreversibel inhibition involves permanent damage to the active site 2. What is a zymogen? 3. How is a zymogen activated? Give some examples of zymogens
1. True 2. A zymogen is an inactive form of an enzyme 3, A zymogen is activated when a part of it is cleaved off. A few examples are digestive enzymes such as a pepsinogen and chymotrypsinogen
