Enzyme Federal mcqs

 1-Allosteric enzymes have.... Major sites 

2

3

4

5

.(2 other sites where non comparative inhibitor binds..2 where inhibitor can bind and regulate enzyme action)

2-Optimum pH for enzyme maltase is 

4.5

5.5

6.1-6.8

6.7-7

(6.1-6.8...)...Federal book line

3-Optimum pH for enzyme Urease is.. 

7.8-8.7

7

4.5

8

Ans=7 federal book line 

4-In plants enzymes become denatured above.....•C

40

50

60

70

.Ans=60 ftb book line 

5-Optimum pH for most enzymes is btw

4-6

6-8

8-10

Neutral 

.......Ans=6-8

 6-Which environment can denature enzyme 

Acidic 

Basic

Neutral 

None... 

......Ans=Acidic

7-Inhibition caused by final end product of reaction is called 

Allosteric inhibition 

Competitive inhibition 

Non competitive inhibition 

None. 

Alpha answer =allosteric inhibition ..Federal book line

8-Non compitative alter St of....

Enzyme 

Active site 

Velocity of enzyme action 

All. 

......All=Ans.   ..Federal book line

9-Poisions like cyanide,heavy metal ions and insecticides r.....inhibitor

Competitive 

Non competative 

Both 

None 

....Ans=none (..Federal book line)

10-Optimum pH for protease 

1

2

3

5

.....Ans=1(   ..Federal book line)

11-Optimum temperature for thermophilic  bacteria is. 

-10 degree 

40 degree 

90 degree 

37 degree

....Ans=90 degree(   ..Federal book line)

12-if the co-factor is small organic molecule it‘s termed as 

Coenzyme 

Activator 

Prosthetic group 

All

...Coenzyme (..Federal book line)

 13-If co-factors ate non-metallic, these are termed as

Prosthetic group 

Activator 

Coenzyme 

A and B

......Prosthetic group (..Federal book line)

14- The absence or presence at second binding site .....enzyme

Activate

deactivate 

Both 

None 

Ans=both (..Federal book line)

15-According to lock and key model enzyme is... And substrate is.. 

Lock-key 

Key-lock 

Both 

None

.....key-lock(..Federal book line)

 16-Cofactors are

 Atoms

Group of atoms

 Molecules

All. 

...Ans=.All(..Federal book line)

17-Copper, zinc, iron are examples of 

Coenzyme 

Prosthetic group 

Activator 

B and C

...prosthetic -non protein(..Federal book line)

18-Rate of enzyme at 0 degree is. 

Zero 

Not zero 

None 

Denatured 

......not zero(..Federal book line)

19-Rate of react depends upon enzyme conc.is 

Linearly 

Curvely 

Both 

None. 

...linearly (..Federal book line)

20-Any molecule that increases the rate of 

a chemical reaction without being used 

up during that reaction is called:

Coenzyme 

 Apoenzyme 

Activator 

Catalyst

....catalyst^

21-Malonic acid is competitive inhibitor of:

Succinic acid 

Fumaric acid 

Succinic dehydrogenase 

Citric acid

.....Sc. dehydrogenase

22-A ⎯⎯→ B ⎯⎯→ C ⎯⎯→ D ⎯⎯→ E 

Deficiency of “E” will control the above 

pathway through:

Feedback mechanism 

 Feedback activation 

Negative feedback 

 Feedback inhibition

....nswer is “Feedback activation”

Explanation: In a chain of biochemical 

reaction, if the end product of last reaction 

is deficient, the first step in the pathway is 

activated.

23-A ⎯⎯→ B ⎯⎯→C ⎯⎯→ D ⎯⎯→ E 

Accumulation of “E” will control the 

above pathway through:

Feedback mechanism 

 Feedback activation 

Negative feedback 

 Feedback inhibition

Answer is “Feedback inhibition”

Explanation: Cell have limited space thus 

product should be produced according to 

need. The excess cause storage disorders. 

Thus upon accumulation of end products, 

the pathway is inhibited from first step and 

this is called feedback inhibition and vice 

versa.

24-Some enzymes are potentially damaging 

if they are manufactured in their active 

form e.g.:

Amylose 

Pepsinogen 

 Pepsin 

Lipase

.....pepsin

 25-Succinic acid dehydrogenase + malonic 

acid ⎯⎯→?

No reaction possible 

 Fumaric acid 

 Enzyme is blocked 

A and C

.....a and C

 26-Pick up the product:

Succinic acid 

Fumaric acid 

 Malonic acid 

Dehydrogenase

......Fumeric acid 

 27-When reactants move more quickly and 

chances of their collision with each 

other are increased as a result the rate 

of enzyme-controlled reactions will?

Decrease initially 

 Increase for ever 

 Increase initially 

 Decrease for ever

...increase initially 

 28-The reaction between _______ activates 

the catalytic site of enzyme.

 Enzyme and substrate 

 Active site of enzyme and substrate 

 Substrate and binding site of enzyme 

 Enzyme and binding site of enzyme

......C... 

29-The charge and shape of the active site 

of the enzyme is formed by _______ in 

the polypeptide chain of the active site 

of the enzyme.

Some amino acids 

 Many amino acids 

 Bulk of amino acids 

 One amino acids

....sone

30-Enzyme was discovered by :

 Freidrich Wilhelm kuhne

 Thomas Cech & Sydney Altman

 Euler

 N.O.T

....none

French chemist Anselme Payen was the first to discover an enzyme, diastase, in 1833.

31-Term enzyme→named by. 

Freidrich Wilhelm kuhne

 Thomas Cech & Sydney Altman

 Euler

 N.O.T

.....Alpha

32- .........discovered Ribozymes

Freidrich Wilhelm kuhne

 Thomas Cech & Sydney Altman

 Euler

 N.O.T.

.....Beta

33-Ratio of concentration of reactant & product

never altered

remains same

Changes 

A and B. 

.....D

34-Which step causes activation of catalytic site of an enzyme?

Change in pH of the surroundings.

Formation of Enzyme Susstrate complex.

Change in the charge of the active site.

Change in temperature

....B

35- The active site of an enzyme:

Never changes

Forms no chemical bond with substrate

Determined by structure and the specificity of the enzyme.

They are non specific in their action.

..C

36-Inhibitors which block the enzyme by forming weak bond are called

Competitive inhibitors.

Non-competitive inhibitors

Irreversible inhibitors.

Both a and B

...D

37-A substance which binds at the active site of the enzyme but does not result in the

formation of the products is called:

Irreversible inhibitor

Reversible inhibitor

Competitive inhibitor

Non-competitive inhibitor

.....C

38-Sucrase (invertase) acts on:

Sucrose

Sucrose and starch

Any disaccharide

 Any organic Monomer

....Sucrose

39-The enzyme used to lyse thrombus is:

a) Asparaginase

b) Streptokinase

c) Hexokinase 

d) CPK

....B

40- About enzyme inhibition, the CORRECT is :

Always reversible

Always irreversible

Reversibility depends on the type of the inhibitor

can be always reversed by addition of more substrate

○.....C

41-About pH effect on enzyme activity include which of the following?

a) shows bell-shaped effect 

b) the enzyme activity is decreased on both sides of the optimum pH

c) the ionization state of the active site of the enzyme is changed 

d) all of the above

.. D

42- The pH optima of the most enzyme is between: )3 مفاضلة)

a) 2 and 4 

b) 8 and 12

c) 5 and 9 (c)

d) 2 and 5 

...6-8 or 5-9

43-The enzyme active site binds substrate by:

a) Weak forces

b) Hydrogen bonds

c) Electrostatic & hydrophobic interactions 

d) all of the above

..All

44-All the following is correct about the active site of enzyme except:

a) Resembles a pocket

b) Resembles cleft

c) Binding site of the substrate 

d) Never binds to cofactor

e) A restricted region of the enzyme

.......D

45-(Km (also known as the Michaelis constant) – the substrate concentration at which the reaction rate is 50% of the Vmax)

 All are correct about competitive inhibitors except:

a) Similar to [s] structure

b) binds to enzyme active site

c) no change in V max 

d) Km is decreased 

.....D

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