Enzymes

Question 1

What is the reaction intermediate species which has the greatest free energy?

Answer 1

transition state

Question 2

What is the reaction CO2 + H20&raquo_space; H2CO3 catalysed by?

Answer 2

carbonic anhydrase

Question 3

Do enzymes affect equilibrium?

Answer 3

NO

Question 4

How do enzymes work?

Answer 4

Enzymes reduce the activation energy by providing alternative reaction pathways

Question 5

What is enzyme without cofactor called?

Answer 5

apoenzyme

Question 6

What is enzyme with cofactor called?

Answer 6

holoenzyme

Question 7

Do cofactors change during a reaction?

Answer 7

Yes but are regenerated

Question 8

What are the 2 types of cofactors?

Answer 8

metal ions

organic molecules

Question 9

What do most vitamins function as?

Answer 9

coenzymes

Question 10

Are coenzymes and cofactors the same?

Answer 10

Yes

Question 11

Is trypsin affected by a small change in pH?

Answer 11

Yes

Question 12

Is LDH a tetramer?

Answer 12

Yes

Question 13

What does increase in LDL suggest?

Answer 13

tissue damage

Question 14

Where is the M form of creatinine kinase produced?

Answer 14

skeletal muscle

Question 15

Where is the B form of creatinine kinase produced?

Answer 15

brain

Question 16

What form of creatinine kinase does the heart produce?

Answer 16

both (MB heterodimer)

Question 17

What are zymogens?

Answer 17

inactive precursors of an enzyme

Question 18

What is the maximal rate of reaction?

Answer 18

Vmax

Question 19

What is the symbol for the Michaelis constant?

Answer 19

Km

Question 20

What is Vo?

Answer 20

initial rate of reaction

Question 21

What does the “S” stand for?

Answer 21

substrate concentrations

Question 22

What is the Michaelis constant (Km)?

Answer 22

the concentration of S which gives ½ Vmax

Question 23

What does a low Km mean?

Answer 23

that an enzyme only needs a little substrate to work at half-maximal velocity

Question 24

With regard to straight lines, how can Vmax be determined?

Answer 24

can be determined from the intersection of the straight line with the Y axis

Question 25

With regard to straight lines, how can Km be determined?

Answer 25

can be determined from the intersection with the X axis

Question 26

What is a reversible inhibitor?

Answer 26

a substance that binds to an enzyme to inhibit it, but which can be released

Question 27

What is an irreversible inhibitor?

Answer 27

a substance that causes inhibition that cannot be reversed

usually involves formation or breaking of covalent bonds to or on the enzyme

Question 28

How can a competitive inhibitor be out competed?

Answer 28

by the addition of lots of substrate

Question 29

Do allosteric enzymes follow Michaelis-Menten kinetics?

Answer 29

No

Question 30

What does increasing substrate result in?

Answer 30

sigmoidal curve, in stead of a hyperbola

Question 31

What is co-operativity?

Answer 31

the influence that the binding of a ligand to one protomer has on the binding of ligand to another protomer in an oligomeric protein

Question 32

What is Binding of oxygen to haemoglobin

an example of?

Answer 32

allosteric regulation

Question 33

Which shows co-operativity, haemoglobin or myoglobin?

Answer 33

haemoglobin

Question 34

In allosteric regulation, what are the two conformations each subunit has? When are the subunits in each form?

Answer 34

R (relaxed): binds substrate tightly; the active form - in presence of substrate
T (tight or taut): binds substrate less tightly; the inactive form - in absence of substrate