2.5 + 8.1 enzymes and metabolism

Question 1

what is anabolism

Answer 1

synthesis of larger molecules from smaller molecules

Question 2

what is catabolism

Answer 2

breaking down complex molecules into smaller molecules

Question 3

what is metabolism

Answer 3

• all enzyme catalysed reactions in a cell
• includes anabolism and catabolism

Question 4

what are enzymes

Answer 4

biological catalysts that increase the rate of reaction without being consumed

Question 5

what are 3 features of enzymes?

Answer 5

1. enzymes lower Ea of reactions
2. enzymes are highly specific as its active site is complementary in shape to its substrate
3. enzymatic activity is lost when denatured due to loss of 3D conformation of active site

Question 6

the two models of enzyme action are…

Answer 6

lock and key, induced fit

Question 7

what does the lock and key model propose?

Answer 7

• the active site is inflexible with a rigid shape
• only substrates with exact shape can fit in active site
• lock = active site on enzyme and key = substrate

Question 8

how does the induced fit model extend the lock and key model?

Answer 8

• increases the range of substrate specificity
• proposes that when a substrate binds to an enzyme, it induces a change in conformation of the enzyme’s active site

Question 9

what affects enzyme activity? (5 briefly)

Answer 9

1. temp
2. pH
3. [substrate]
4. [enzyme]
5. [enzyme inhibitor]

Question 10

how does temp affect enzyme activity?

Answer 10

• incr temp -> incr kinetic energy
• thus incr rate of effective collisions btw substrates and enzymes

Question 11

how does pH affect enzyme activity?

Answer 11

• pH affects the structure of the enzyme
• drastic pH changes can cause denaturation, changing the shape of the active site

Question 12

what is the effect of increasing [substrate]?

Answer 12

• incr substrate leads to more chances of effective collisions w enzymes -> incr the % of active sites occupied
• at high [substrate] there is saturation of all active sites

Question 13

how do competitive inhibitors work?

Answer 13

they compete with the substrate at the active site

Question 14

how do non competitive inhibitors work?

Answer 14

they bind to the allosteric site to alter the shape of the active site

Question 15

_________ inhibition can be overcome by increasing [substrate]

Answer 15

competitive

Question 16

what is a structural feature of competitive inhibition that enables it to function as a competitive inhibitor?

Answer 16

the inhibitor and substrate are similar in shape

Question 17

the synthesis of isoleucine from threonine involves _________ inhibition

Answer 17

end product

Question 18

end product inhibitors are typically _________ inhibitors

Answer 18

non-competitive

Question 19

how does end product inhibition control metabolism?

Answer 19

• end product of a metabolic pathway acts as an inhibitor of the first enzyme in the pathway
• accumulation of end product incr its chances of inhibiting the enzyme to stop the metabolic pathway

Question 20

what is a metabolic pathway?

Answer 20

a chain of enzyme-catalysed reactions

Question 21

in the synthesis of isoleucine, who is the end product inhibitor?

Answer 21

isoleucine

Question 22

what enzyme is used in the synthesis of isoleucine?

Answer 22

threonine deaminase

Question 23

isoleucine is an [competitive/non-competitive] inhibitor

Answer 23

non-competitive

Question 24

explain the end product inhibition of isoleucine

Answer 24

• isoleucine is synthesised from threonine
• isoleucine is non competitive inhibitor of threonine
• binds to allosteric site of threonine deaminase,
  the enzyme in the first step
• stops the metabolic pathway

Question 25

what are 2 ways enzymatic reactions can be tracked?

Answer 25

measure
1. rate of pdt formed
2. rate of disappearance of substrate

Question 26

why are enzymes immobilised (brief)

Answer 26

1. so they can be reused
2. so the reaction can be stopped quickly by removing the enzyme

Question 27

what is an example of enzyme immobilisation in the industry?

Answer 27

lactose-free milk

Question 28

who needs lactose-free milk

Answer 28

individuals w lactose intolerance

Question 29

how is lactose-free milk produced?

Answer 29

regular milk with lactose is passed over immobilised lactase