8.1

Question 1

what are cycles?

Answer 1

• where a start molecule is changed over a series of reactions and reformed
• allowing continuous pathway

Question 2

what are chains?

Answer 2

• where a start molecule changed over a series of reactions to form an end molecule

Question 3

what are enzymes?

Answer 3

proteins that speed up the rate of reactions by lowering the activation energy

Question 4

how do enzymes lower the activation energy?

Answer 4

by colliding with substrates at the active site that have
1. a complementary shape and charge
2. the correct orientation
3. sufficient energy

Question 5

what are the 2 binding of substrate theories?

Answer 5

1. lock and key mechanism
2. induced fit mechanism

Question 6

describe the lock and key mechanism

Answer 6

• states that the active site has an exact fit with the substrate
• it is the binding of substrates with complementary shape and charge

Question 7

describe the induced fit mechanism

Answer 7

• the binding of substrates with complementary shape and charge
• states that the active site has an approximate fit with the substrate
• molds to fit the substrate as it successfully collides
• it is regarded to be more accurate

Question 8

why do enzymes need to be inhibited at times?

Answer 8

• to control the metabolic pathway
• prevent unnecessary production

Question 9

what are the 2 types of inhibition?

Answer 9

1. competitive
2. non-competitive

Question 10

describe the process of competitive inhibition

Answer 10

1. the inhibitor molecule is similar in shape and charge to the substrate
2. as a result, it is able to bind to the active site and occupy it for a period of time
3. this therefore, slows down the reaction because it prevents the substrate from binding and undergoing catalysis

Question 11

what is an ib example of a competitive inhibition

Answer 11

the conversion of succinate to fumarate

Question 12

describe the process of the conversion of succinate to fumarate

Answer 12

• malonate is the competitive inhibitor that binds to the enzyme
• this prevents succinate from binding

Question 13

describe the process of non-competitive inhibition

Answer 13

1. the inhibitor molecule binds to a secondary site on the enzyme (allosteric site)
2. binding to this site triggers a change in enzyme conformation
3. resulting in the change in active site shape
4. this means that it can no longer mold to fit the substrate and thus completely prevents the reactions from occurring

Question 14

what is the ib example for a non-competitive inhibition?

Answer 14

the conversion of triose phosphate to pyruvate

Question 15

describe the process of the conversion of triose phosphate to pyruvate

Answer 15

• alanine binds to the allosteric site of pyruvate kinase
• prevents triose phosphate from binding

Question 16

what is the end-product inhibition and why is this type of non-competitive inhibition useful?

Answer 16

• when the end product of a chain inhibits the enzyme involved in the first reaction
• it is very effective at controlling the concentration of all the molecules in the pathway

Question 17

describe the rate of reaction during competitive inhibition

Answer 17

1. rate increases at a slower rate due to blocking of the active site
2. as substrate concentration increases, it begins to outcompete the inhibitor for the active site
3. therefore, it is able to reach the same maximum rate at a high substrate concentration

Question 18

describe the rate of reaction during non-competitive inhibition

Answer 18

1. rate increases at a much slower rate due to the changes in the active site of multiple enzymes
2. as substrate concentration increases, unaffected enzymes collide more frequently with the substrate
3. however, this means only a certain number of enzymes reach maximum rate
   - which will be lower than that of competitive inhibition