EASY
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Enzymes from bacteria that live in hot springs may have optimums as low as -75°C.

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Important Questions on Enzymes

HARD
Given below are the four schematics that describe the dependence of the rate of an enzymatic reaction on temperature. Which of the following combination is true for thermophilic and psychrophilic organisms?

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MEDIUM

The graph given below shows the Michaelis-Menten kinetics for two reactions (R1 and R2; represented as solid and dotted lines, respectively). Enzymes E1 and E2 have Vmax values, Vmax1 and Vmax2, respectively. The respective KM values for E1 and E2 are KM1 and KM2. (KM1=KM2).

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The correct statement(s) for reactions R1 and R2 is/are

MEDIUM

Given below are two statements :

Statement I : Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

Statement II : When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor.

In the light of the above statements, choose the correct answer from the options given below : 

HARD
Write briefly about the enzyme inhibitors.
MEDIUM
Match the following lists.
  List-I   List-II   List-III
A Coenzymes are organic compound i No structure similarities I Ribose-5 phosphate isomerase
B Isomerases ii Differ from inorganic catalysis II During catalysis
C Non-competitive enzyme inhibition iii Catalyzing interconversion of optical positional isomers III Operates at high temperatures also
D Enzyme catalysts iv With the apoenzyme only as a transient IV Metal ion of copper

The correct match is:

MEDIUM
Solid and dotted lines represent the activities of pepsin and salivary amylase enzymes of the digestive tract, respectively. Which one of the following graphs best represents their activity vs pH?
HARD

A scientist performed enzyme kinetics and obtained velocityv as a function of substrate concentration [S] and the values are given in the table below.

S(μMolar)  v (μ/min) S(μMolar)  v (μ/min)
50 10.2 400 62.5
100 19.1 800 75.3
150 31.2 1000 76.2
200 38.1 1300 76.3
300 55.4 1600 77.2

The Km of the substrate could

HARD
Write briefly about enzyme inhibitors.
HARD
Write briefly about enzyme inhibitors.
HARD

The following graph shows the concentration of substrate on enzyme activity:

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What does the Y-axis represent?

MEDIUM

The graph below depicts the velocity of an enzyme-catalyzed reaction vs. substrate concentration. Identify the alphabets with the correct descriptions.

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I. A= Enzyme activity

II. B= Substrate concentration at maximum velocity

III. A= Substrate concentration at which half of the maximum velocity

IV. B= Half of the maximum velocity

HARD
In an organism, enzymes generally have
MEDIUM
Select the right option regarding the given graph.
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  X Y
(i) Rate of reaction Enzymatic activity
(ii) Enzymatic activity Rate of reaction
(iii) Enzymatic activity pH /Temperature
(iv) pH /Temperature Enzymatic activity
MEDIUM
Which one of the given graph shows the effect of pH on the velocity of a typical enzymatic reaction (V) ?
MEDIUM
Which of the following graphs shows the relationship between the rate of an enzymatic activity and substrate concentration (S)?
EASY
The curve given below shows enzymatic activity with relation to three conditions (pH, temperature and substrate concentration). What do the two axes (X and Y) represent?

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EASY
 The activity of enzymes increases on increasing all the following factors, except 
HARD
Describe the factor affecting enzyme action.
MEDIUM
What will happen if starch amylase mixture is incubated at 0°c for half an hour?