Enzymes

Question 1

what do enzymes do?

Answer 1

speed up the rate at which a reaction reaches equilibrium

Question 2

what do enzymes bind to and what do they do to this molecule?

Answer 2

the transition state

they stabilize it

Question 3

what is the transition state?

Answer 3

the reaction intermediate species with the greatest free energy

Question 4

what do enzymes reduce and how?

Answer 4

the activation energy

by providing alternative reaction pathways

Question 5

what is glycogen storage disease?

Answer 5

an enzyme deficiency that results in the failure of glycogen to enter its transition state

this results in defective synthesis and breakdown of glycogen

Question 6

how many types of glycogen storage diseases are there and why?

Answer 6

11

due to defects in 12 glycogen/glucose metabolising enzymes

Question 7

what is the most common glycogen storage disease and describe its symptoms?

Answer 7

von gierke’s disease

hypoglycaemia, ulcers, hepatomegaly, bowel inflammation

Question 8

how are glycogen storage diseases treated?

Answer 8

slow release glucose meals

feed little and often to mimic glycogen conversion to glucose

Question 9

what are cofactors?

Answer 9

inorganic metal ions that may be needed for enzyme function

Question 10

what are coenzynes?

Answer 10

organic molecules that may be needed for enzyme function

Question 11

what are tightly bound coenzymes called?

Answer 11

prosthetic groups

Question 12

what is an enzyme without a cofactor called?

Answer 12

an apoenzyme

Question 13

what is an enzyme with a cofactor called?

Answer 13

a holoenzyme

Question 14

what do active sites contain that enzymes require?

Answer 14

amino acids for catalytic activity and for specific interactions

Question 15

where does a substrate bind to an enzyme?

Answer 15

the active site

Question 16

what two models are used to describe how an enzyme binds to a substrat?

Answer 16

lock and key

induced fit

Question 17

describe the lock and key model

Answer 17

the active site of the unbound enzyme is complementary to the shape of the substrate

Question 18

describe the induced fit model

Answer 18

binding of the substrate induces a conformational change in the enzyme, resulting in a complimentary fit

Question 19

what are isozymes?

Answer 19

isoforms of enzymes

catalyse the same reaction but have different structure and properties

Question 20

name a protein thats isozymes can be used for diagnostic purposes

Answer 20

creatinine kinase

Question 21

what are the two isoforms of CK and where are they made?

Answer 21

M form in skeletal muscle (MM)

B form in the brain (BB)

Question 22

what type of CK is made by the heart?

Answer 22

both, forms a heterodimer (MB)

Question 23

what does appearance of BB CK in the blood suggest?

Answer 23

a stroke or brain tumour

Question 24

what does the appearance of MB CK In the blood suggest?

Answer 24

MI

Question 25

what carries out phosphorylation?

Answer 25

protein kinases

Question 26

what are zymogens?

Answer 26

inactive enzyme precursors

Question 27

how are zymogens activated?

Answer 27

cleavage of a covalent bond

Question 28

what is Vmax?

Answer 28

the maximum velocity of a reaction

Question 29

what is Km?

Answer 29

the concentration of a substrate which gives half Vmax

Question 30

where is Vmax found when plotted on a straight line graph?

Answer 30

the Y intersection

Question 31

where is Km found when plotted on a straight line graph?

Answer 31

the x intersection

Question 32

what does a low Km suggest?

Answer 32

enzyme needs a little substrate to work at a half maximal velocity

Question 33

what does a high Km suggest?

Answer 33

enzyme needs a lot of substrate to work at half-maximal velocity

Question 34

what are the two classes of inhibition?

Answer 34

reversible

irreversible