Unit 1: Enzymes and Catalysis

Question 1

rate of a chemical reaction

Answer 1

• amount of product formed per unit of time

Question 2

enzymes

Answer 2

• a protein that functions as a catalyst to accelerate the rate of a chemical reaction
• enzymes are critical in determining which chemical reactions take place in a cell
• speed up reaction rates by decreasing the required activation energy of a chemical reaction, enzymes do not change thermodynamics of a reaction (change in free energy is the same with and without the enzyme)

Question 3

exergonic reactions

Answer 3

• release free energy

Question 4

endergonic reactions

Answer 4

• requires free energy

Question 5

enzyme active site

Answer 5

• enzyme’s active site forms a complex with the substrates (reactants) and helps push them into position that mimics the products (transition state)

Question 6

transition state (3)

Answer 6

• brief time in a chemical reactions where existing chemical bonds in the reactants are broken and new bonds in the products are formed
• it is largely unstable and has a large amount of free energy
• in an uncatalyzed reaction, this state is very high energy and very unstable, making it hard to acheive

Question 7

activation energy (3)

Answer 7

• energy that must be input or achieved for the transition state to form
• energy barrier that must be overcome for the reaction to proceed
• lowering the activation energy means a faster reaction

Question 8

enzyme function

Answer 8

• make the transition state for stable: less activation energy is required for the transition state to form, and the reaction proceeds quickly

Question 9

enzyme catalysis steps

Answer 9

1) initiation: enzyme loosely binds the substrate(s) in a specific orientation forming an “enzyme-substrate complex”
2) Transition state stabilization: enzyme cranks the substrate(s) into the transition state, essentially making the transition state “less unstable”
3) termination: the reaction proceeds, the products are released, and the enzyme returns to its starting position

Question 10

conformation change (shape change)

Answer 10

• binding of substrates in an active site of enzymes triggers this in the enzyme
• make the TS more stable as it binds Ts more tightly together

Question 11

enzyme inhibition

Answer 11

• small molecules that regulate enzyme activity

- inhibition is usually reversible, the effects of the inhibitor can be removed by the inhibitor removing itself

Question 12

competitive inhibitors

Answer 12

• competes with the normal substrate for the enzyme’s active site
• bind using non-covalent interactions

Question 13

non-competitive inhibitors

Answer 13

• binds to the enzyme at a site that is not the active site

- bind using non-covalent interactions

Question 14

allosteric enzymes

Answer 14

• enzymes can be regulated up or down by the presence of signal molecules
• negative and positive feedback systems