Enzymes

Question 1

how does an enzyme work ?

Answer 1

• enzymes decrease activation energy = increasing rate of reaction

Question 2

what is the lock and key hypothesis ?

Answer 2

• active site has rigid shape
• substrate shape is complementary to active site
• ESC is formed then EPC

Question 3

what is the induced fit hypothesis ?

Answer 3

• active site is flexible
• active site changes shape to fit substrate
• ESC then EPC formed

Question 4

how does pH affect enzyme activity ?

Answer 4

• enzymes active at optimum pH
• high or low pH can denature enzymes as tertiary structure is disrupted

Question 5

how does temperature affect enzyme activity ?

Answer 5

• high temperature = denaturation
• inc temp - inc ke more frequent collisions

Question 6

what is an apoenzyme ?

Answer 6

• inactive protein part of an enzyme
• needs a cofactor to be active

Question 7

what is a holoenzyme ?

Answer 7

• enzyme along with cofactor

Question 8

what is a cofactor ?

Answer 8

• either organic or inorganic
• help enzyme function

Question 9

what is an inorganic cofactor ?

Answer 9

• metal ions
• eg. Zn2+ for carbonic anhydrase

Question 10

what is an organic cofactor ?

Answer 10

• prosthetic groups (heam)
• coenzyme (NAD)

Question 11

what is the difference between prosthetic groups and co-enzymes ?

Answer 11

• co-enzymes are temporarily bound whereas prosthetic groups are tightly bound

Question 12

what are the 6 classifications of enzymes ?

Answer 12

• Ligase
• Isomerases
• Lyase
• Hydrolases
• Oxidoreductases
• Transferases

Question 13

what are transferase enzymes ?

Answer 13

• transfer a functional group between molecules
• eg. kinases transfer phosphate groups

Question 14

what are ligase enzymes ?

Answer 14

• catalyse synthesis of new covalent bonds using ATP
• eg. DNA Ligase

Question 15

what are oxidoreductase enzymes ?

Answer 15

• catalyse transfer of electrons
• eg. lactate dehydrogenase

Question 16

what are isomerase enzymes ?

Answer 16

• catalyse conversion of isomers, transferring groups within the same molecule
• eg. cis trans isomers

Question 17

what are hydrolase enzymes ?

Answer 17

• addition of water to break bonds

Question 18

what are 3 types of hydrolase enzymes ?

Answer 18

• phosphatases (ester bonds)
• lipases (ester bonds - lipids)
• peptidases (peptide bonds - forms 2 products )

Question 19

what are lyase enzymes ?

Answer 19

-catalyse addition or removal of H20 , CO2 , NH3 to create double bonds

• eg. dehydrase, decarboxylase. deaminase

Question 20

what are Isoenzymes ?

Answer 20

• different amino acid sequence but catalyse the same reaction

Question 21

what is allosteric regulation ?

Answer 21

• effector can bind to allosteric site and either speed up or slow down action

Question 22

what is feedback inhibition ?

Answer 22

• the end product binds to an enzymes at the start of the pathway to stop further synthesis

Question 23

What do kinase enzymes do?

Answer 23

• Add phosphate groups