Enzyme catalysis - class-XI
Description: enzyme catalysis | |
Number of Questions: 52 | |
Created by: Seema Agrawal | |
Tags: chemistry surface chemistry biochemistry |
According to the adsorption theory of catalysis, the rate of reaction increases with the use of a catalyst because:
-
the heat liberated during adsorption increases the rate of reaction
-
the kinetic energy of reactants increases which increases the rate of reaction
-
the activation energy of reaction increases which increases the rate of reaction
-
the concentration of reactants at the active centers becomes high due to adsorption the rate of reaction
Adsorption theory of Heterogeneous catalysis involves five steps-
- Diffusion of reactants to the surface of the catalyst.
- Adsorption of reactant molecules on the surface of the catalyst. (Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate.
- Desorption of reaction products from the catalyst surface, and thereby, making the surface available again for more reaction to occur.
- Diffusion of reaction products away from the catalyst’s surface.
- So, we can deduce from Adsorption theory of catalysis that as the concentration of reactants at active centers increases due to adsorption and thus the rate of the reaction is also increased.
Match the column I and column II and mark the appropriate choice.
Column I | Column II |
---|---|
(A) Diastase | (i) Proteins $\rightarrow$ peptones |
(B) Pepsin | (ii) Glucose $\rightarrow$ ethyl alcohol |
(C) Ptyalin | (iii) Starch $\rightarrow$ maltose |
(D) Zymase | (iv) Starch $\rightarrow$ sugar |
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(A) $\rightarrow$ (iv), (B) $\rightarrow$ (ii), (C) $\rightarrow$ (i), (D) $\rightarrow$ (iii)
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(A) $\rightarrow$ (ii), (B) $\rightarrow$ (i), (C) $\rightarrow$ (iv), (D) $\rightarrow$ (iii)
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(A) $\rightarrow$ (i), (B) $\rightarrow$ (ii), (C) $\rightarrow$ (iii), (D) $\rightarrow$ (iv)
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(A) $\rightarrow$ (iii), (B) $\rightarrow$ (i), (C) $\rightarrow$ (iv), (D) $\rightarrow$ (ii)
- Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products.
- Diastace converts $Starch\rightarrow maltose$
- Pepsin converts $Proteins\rightarrow peptones$
- Ptyalin converts $Starch\rightarrow sugar$
- Zymase converts $Glucose\rightarrow ethyl alcohol$
- Invertase converts $Cane sugar\rightarrow Glucose+Fructose$
The activity of an enzyme becomes ineffective:
-
at low temperature
-
at atmospheric pressure
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at high temperature
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in aqueous medium.
- Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products.
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Enzymes are Highly specific nature.
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Enzymes are highly active under optimum temperature.
- Enzymes are highly active under optimum pH.
- The activity of enzymes gets increased in presence of activators and co-enzymes.
Which of the following is not correct for enzyme catalysis?
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The enzyme activity is maximum at optimum pH which is between 5-7.
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Each enzyme is specific for a given reaction.
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The favourable temperature range of enzyme activity is between 50-60$^{\circ}$C.
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The enzymatic activity is increased in presence of certain substances called co-enzymes.
- Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products.
-
Enzymes are Highly specific nature.This says that enzyme is specific for a given reaction.
- Enzymes are highly active under optimum temperature.The optimum temperature range for enzymatic activity is 298-310K.
- Enzymes are highly active under optimum pH.Optimum pH level is between 5-7.
- The activity of enzymes gets increased in presence of activators and co-enzymes.
Identify the correct statement regarding enzymes.
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Enzymes are specific biological catalysts that possess well defined active sites.
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Enzymes are normally heterogeneous catalysts that are very specific in their action.
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Enzymes are specific biological catalysts that cannot be poisoned.
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Enzymes are specific biological catalysts that can normally function at very high temperature (T=1000K).
- Enzyme catalysis is unique in its efficiency and a high degree of specificity.
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Most highly efficient: One molecule of an enzyme may transform one million molecules of the reactant per minute.
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Highly specific nature: Each enzyme is specific for a given reaction, i.e., one catalyst cannot catalyse more than one reaction.
-
Highly active under optimum temperature: The rate of an enzyme reaction becomes maximum at a definite temperature, called the optimum temperature.
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Highly active under optimum pH: The rate of an enzyme-catalysed reaction is maximum at a particular pH called optimum pH, which is between pH values 5-7.
- Enzymes are normally homogeneous catalysts.
Some drugs do not bind the enzyme's active site, instead, bind to a different site of an enzyme. This site is called:
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allosteric site
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substrate site
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ionic site
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competitive site
A substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction.
Determine the surface area of a catalyst that adsorbs $10^3cm^3$ nitrogen at STP per gram in order to form mono layer. The effective area occupied by nitrogen molecule on the surface is $0.1602\times { 10 }^{ -14 }\quad { cm }^{ 2 }$
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$579m^2$
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$449 m^2$
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$579cm^2$
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none of these
Enzymes in the living systems:
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provide energy
-
provide immunity
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transport oxygen
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catalyse biological reactions
Enzymes in the living systems catalyse biological reactions.
The efficiency of an enzyme to catalyse a reaction is due to its capacity to:
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Reduce the activation energy of the reaction
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Form strong enzyme-substrate complex
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Decrease the bond energies of all substrate molecules
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Alter the substrate geometry to fit into the shape of the enzyme molecule
Enzymes are catalysts for biological reactions. Catalysts have the ability to lower the activation energy barrier of the reaction. The more it reduces the activation energy barrier the more efficient it will be.
The temperature at which the enzyme shows maximum activity is known as _____________ temperature.
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critical
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supportive
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optimum
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none of the above
Each enzyme has a temperature range in which a maximal rate of reaction is achieved. This maximum is known as the optimum temperature of the enzyme. The optimum temperature of each enzyme is different
The effectiveness of a catalyst is minimum at its optimum temperature.
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True
-
False
A catalyzed reaction rate is much faster at the optimum temperature of an enzyme. This is a result of increased catalyst activity due to its maximum effectiveness at the optimum temperature
Select the incorrect statement(s).
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Enzyme catalysed reactions are usually hydrolytic in nature
-
Enzyme catalysed reactions takes place with evolutions of gases
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The rate of reaction does not depend upon enzyme concentration
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Enzymes are colloidal in nature
The rate of enzyme catalysed reaction depends upon enzyme concentration.
Which of the following is true?
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Enzymes are non - proteinaceous nitrogen containing compounds.
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Amylase convert starch into amylose.
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Biocatalysts, catalyse the reaction occurring in living beings.
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Enzymes are not found in plants.
Enzyme activity is highest in the temperature range of:
-
$0-15^o$C
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$15-25^o$C
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$25-45^o$C
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remain same in all
In conversion of sucrose to glucose, the enzyme is:
-
zymase
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lipase
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invertase
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diastase
The Enzyme Invertase is used for the conversion of Sucrose to Glucose.
Incorrect statement about a catalyst is?
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It does not alter Gibbs energy, $\Delta G$ of a reaction
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it catalyses both spontaneous and non-spontaneous reactions
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A small amount of catalyst can catalyse a large amount of reaction
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It does not affect equilibrium constant of a reaction
How do enzymes increase the rate of reaction?
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By lowering activation energy
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By increasing activation energy
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By changing equilibrium constant
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By forming enzyme substrate complex
Enzyme catalysis is the increase in the rate of a chemical reaction by the active site of a protein. The protein catalyst (enzyme) may be part of a multi-subunit complex, and/or may transiently or permanently associate with a Cofactor (e.g. adenosine triphosphate). Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions. A key driver of protein evolution is the optimization of such catalytic activities via protein dynamics.
They decrease activation energy by providing alternate pathway for process and hence, increase the rate of reaction.
The enzyme ptyalin used for digestion of food is present in:
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saliva
-
blood
-
intestine
-
adrenal gland
They decrease the activation energy by providing alternate pathway (enzyme reacts with the substrate to form an intermediate ES complex, which would be impossible in the absence of the enzyme) for the process.
Enzyme + Substrate → Complex → Product + Enzyme
Which statement about enzymes is not correct?
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Enzymes are in colloidal state.
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Enzymes are catalysts.
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Enzymes can catalyse any reaction.
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Urease is an enzymes.
Enzymes are proteins and are giant molecules making them colloidal particles. They are shape selective and catalyzes a specific reaction in which they are suitable. But they cannot catalyze any reaction.
Bacterial infection on eye surface is protected by the enzyme :
-
urease
-
carbonic anhydrase
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lysozyme
-
xymase
They decrease activation energy by providing alternate pathway (enzyme reacts with the substrate to form an intermediate ES complex, which would be impossible in the absence of the enzyme) for the process.
Conjunctiva (membrane covering the eye) is protected by lysozyme and defensin enzymes. However, when these protective barriers fall, conjunctivitis results.
Identify the correct statement regarding enzymes.
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Enzymes are specific biological catalyst that possess well defined active state.
-
Enzymes are normally heterogeneous catalyst that are very specific in their action.
-
Enzymes are specific biological that cannot be poisoned.
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Enzymes are specific biological catalyst that can normally function at very high temperature $ ( T \simeq 1000 K).$
They decrease activation energy by providing alternate pathway (enzyme reacts with the substrate to form an intermediate ES complex, which would be impossible in the absence of the enzyme) for the process.
Enzymes in the human body function as a catalyst.
-
True
-
False
Catalysts increase the rate of a reaction by providing an intermediate to be formed, although the catalyst is left unchanged at the end of the reaction. Catalysts speed up reactions, and without them these reactions might be too slow to sustain life processes.
An enzyme is a protein which has a highly specific amino acid sequence as well as 3D structure allowing it to catalyse reactions. In this sense, they are biological catalysts.
Examples of enzymes are DNA Polymerases (which replicate our DNA to allow our cells to divide) and Kinases (which add phosphate groups to other proteins that might be part of a signalling pathway).
Which requires catalyst
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$S+O _2 \rightarrow SO _2$
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$2SO _2+O _2 \rightarrow 2SO _3$
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$C+O _2 \rightarrow CO _2$
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All
Catalyst makes the reaction more exothermic.
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True
-
False
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Ambiguous
-
Data insufficient
The statement is false.
Catalyst does not makes the reaction more exothermic.
A catalyst can lower the activation energy required for the reaction to take place and allows the reaction to reach equilibrium faster, but as the catalyst is unchanged at the end of the reaction, the total energy absorbed or released during the reaction will be the same.
-
True
-
False
Enzyme catalysed reactions are highly specific. Just as a key is used or a particular lock, each enzyme is used for specific reaction.
Transition metals are more efficient catalyst.
-
True
-
False
-
Ambiguous
-
Data insufficient
Transition metals are more efficient catalyst as they have vacant d- orbitals. The ability of transition metals to form more than one stable oxidation state means that they can accept and lose electrons easily. This enables them to catalyze certain redox reactions. They can be readily oxidized and reduced again, or reduced and then oxidized again, as a consequence of having a number of different oxidation states of similar stability. They can behave either as homogeneous catalysts or as heterogeneous catalysts.
-
True
-
False
Zymase is an enzyme complex that catalyses the fermentation of glucose into ethanol and carbon dioxide. It occurs naturally in yeasts.
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True
-
False
Enzymes also act as catalyst in biological process. Enzymes are biological molecules that act as catalysts and help complex reactions to proceed faster without altering the rate of reaction.
During the process of digestion, the protein present in food materials are hydrolysed to amino acids. The two enzymes involved in the process are:
Proteins $\xrightarrow [ ]{ Enzyme\quad (A) } $ Polypeptides
$\xrightarrow [ ]{ Enzyme\quad (B) } $ Amino acids
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Invertase and zymase
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Amylase and maltase
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Diastase and lipase
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Pepsin and trypsin
Which of the following belong(s) to the family of enzymes?
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Lipase
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Pepsin
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Ptylin
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Cellulose
Enzymes are ____ specific in action.
-
highly
-
not
-
may be
-
may not
Enzymes are highly specific in action.
Almost every biochemical reaction is controlled by its own specific enzymes.
Thus, the enzyme urease catalyzes the hydrolysis of urea. No other enzyme catalyzes this reaction.
The function of enzymes in the non-living system is to:
-
transport oxygen
-
provide immunity
-
catalyse biochemical reaction
-
none of the above
A fundamental task of proteins is to act as enzymes catalysts that increase the rate of virtually all the chemical reactions within cells. Although RNAs are capable of catalyzing some reactions, most biological reactions are catalyzed by proteins. In the absence of enzymatic catalysis, most biochemical reactions are so slow that they would not occur under the mild conditions of temperature and pressure that are compatible with life. Enzymes accelerate the rates of such reactions by well over a million-fold, so reactions that would take years in the absence of catalysis can occur in fractions of seconds if catalyzed by the appropriate enzyme.
In a fermentation tank, molasses solution is mixed with yeast enzymes. After three days alcohol was observed. The speed of the reaction in this case is:
-
slow
-
medium
-
fast
-
very fast
The maximum concentration of alcohol possible through a natural fermentation is about $12\%$ ethanol,
Starch converts into maltose by the catalytic action of the enzyme:
-
maltase
-
zymase
-
diastase
-
lipase
Name of an enzyme used to dissolve the blood clot is :
-
streptokinase
-
amylases
-
invertase
-
phenylketoneurea
Streptokinase is used to dissolve blood clots that have formed in the blood vessels. It is used immediately after symptoms of a heart attack occur to improve patient survival. This medicine may also be used to treat blood clots in the lungs (pulmonary embolism) and in the legs (deep venous thrombosis).
An enzyme present in the saliva of human beings is :
-
thiamine
-
riboflavin
-
amylases
-
none of these
Ptyalin is the starch hydrolyzing enzyme secreted by salivary glands in human beings. It is also called as salivary amylase. Ptyalin secreted in the mouth brings about digestion of starch in the mouth itself.
Active sites are essential for enzyme action.
-
True
-
False
Holoenzymes are complete and active enzymes.
-
True
-
False
True, Holoenzymes are complete and active enzymes.
Metal ions can activate enzymes.
-
True
-
False
Yes, Metals ion can active enzymes.
$Cl^-$ ions act as activators for:
-
amylases
-
peptidases
-
glycosidases
-
lipases
$Cl^{-}$ ions act as activators for amylase enzyme.
The temperature at which the catalytic activity of the catalyst is maximum, is called:
-
critical temperature
-
room temperature
-
absolute temperature
-
optimum temperature
Some catalysts are, however, physically altered by a rise in temperature and hence their catalytic activity may be decreased. This is particularly true with colloidal solutions like that of platinum, since a rise in the temperature may cause their coagulation. In such a case, the rate of reaction increases up to a certain point and then gradually decreases. The rate of reaction is maximum at a particular temperature; that is Optimum temperature.
Which one of the following statements is false?
-
Enzymes arc highly specific
-
Enzymes increase activation energy
-
Enzymes require optimum temperature
-
None of the above
- Enzymes serve as a biological catalyst by accelerating the rate of chemical reaction occurring inside the cells of living organisms, thus decreasing the activation energy required for the reaction to occur.
- Enzymes are very specific in nature, implying that, a particular enzyme can catalyze only a specific reaction and not all the reactions.
-
The optimum temperature for an enzyme to function effectively is $37.5^o C$ which is also the normal human body temperature. At a temperature above this, enzymes undergo denaturation, thus, showing a reduced performance
Which of the following catalysts is sensitive to temperature changes?
-
Enzymes
-
$Pt, Fe$
-
$Ni, Fe$
-
All of the above
Enzymes are specific in their action and catalyze reactions at lower temperature. At high temperature, they lose their specific nature and get denatured.
The function of zymase is to:
-
change starch into sugar
-
ferment glucose to alcohol and carbon dioxide
-
change malt sugar into glucose
-
change starch into malt sugar and dextrin
Zymase is an enzyme complex that catalyzes the fermentation of sugar into ethanol and carbon dioxide.
Hence option B is correct.
The enzyme ptyalin used for digestion of food is present in:
-
saliva
-
blood
-
intestine
-
adrenal glands
The enzyme ptyalin, also known as amylase is present in saliva and is responsible for breaking down starch into simple sugars such as dextrin and maltose which are further broken down in the intestine
The function of enzymes in the living system is to________.
-
Transport oxygen
-
Provide immunity
-
Catalyse biochemical reaction
-
Provide energy
The function of enzymes in the living system is to catalyse biochemical reaction.
Enzymes are highly substrate specific and catalyze reactions by providing an alternate pathway of lower activation energy.
A catalyst increases the rate of reaction by_________.
-
Decreasing enthalpy
-
Decreasing internal energy
-
Decreasing activation energy
-
Increasing activation energy
A catalyst increases the rate of reaction by decreasing activation energy.
Note: The function of enzymes in the living system is to catalyse biochemical reaction.
Enzymes are highly substrate specific and catalyze reactions by providing an alternate pathway of lower activation energy.
Identify the correct statement regarding enzymes:
-
Enzymes are specific biological catalysts that can normally function at very high temperature
-
Enzymes are normally heterogeneous catalysts that are very specific in action.
-
Enzymes are specific biological catalysts that cannot be poisoned
-
Enzymes are specific biological catalysts that possess well defined active site
Enzymes are specific biological catalysts that possess well defined active site.
Enzymes function at physiological temperature $ \displaystyle \simeq (37 : ^oC)$
-
Enzymes arc biological catalysts found in organisms
-
All enzymes are proteins
-
Enzymes can catalyse any reaction
-
Enzymes activity is optimum at $37^o C $
Which of the following statements regarding enzyme inhibition is correct -
-
Competitive inhibition is seen when a substrate competes with an enzyme for
binding to an inhibitor protein -
Non-competitive inhibitors often bind to the
enzyme irreversibly -
Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme
-
Non-competitive inhibition of an enzyme can be overcome by adding large amount of substrate
Enzymes, which catalyze biochemical reactions are very complex. They help in the reaction of very specific substances. This suggests that the enzyme and the reacting biochemicals are complementary to one another like a:
-
dog in his kennel
-
horse and a rider
-
lock and key
-
leaf and a bud
Enzymes are very specific in nature. Only those substrates that can fit into the active site of an enzyme can be bound within it. This specific action is similar to a lock and key where a key(reacting biochemicals) can only be used to actuate a specific lock(enzyme) and not all of them.
Which of the following factors are responsible for the increase in the rate of a surface catalysed reaction?
I. A catalyst provides proper orientation for the reactant molecules to react
II. Heat of adsorption of reactants on a catalyst helps reactant molecules to.overcome activation energy
III. The catalyst increases the activation energy of the reaction
IV. Adsorption increases the local concentration of reactant molecules on the surface of the catalyst
Select the correct answer using the codes given below:
-
I and II
-
I and III
-
I, II and IV
-
I, II and III
A catalyst works by providing an alternative reaction pathway to the reaction product. The rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.