Test: Respiration & Enzymes- 1

30 Questions MCQ Test Botany for Class 11 - Notes and Tests | Test: Respiration & Enzymes- 1

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What is the importance of respiration in organisms?


Respiration is a catabolic process, which oxidises reduced substrates, thus, resulting in the energy stored in reduced substrates. The reduced substrates are produced by the process of photosynthesis occurring in green plants and the reduced substrates are oxidised through respiration releasing CO2, water vapour and energy in the form of ATP.
So, the correct answer is 'It liberates CO2'


An indispensible role in energy metabolism is played by


Plants require a number of mineral elements for optimum growth and activity. Phosphorous is an essential macro nutrient. It is a component of energy rich nucleotides, like ATP, GTP etc. 
Phosphorous participates in all the reactions, where energy is either evolved or consumed. Hence, phosphorous plays an indispensable role in energy metabolism of a cell.


Energy obtained by a cell from catabolic reaction is stored immediately in the form of


Which component of ETS is mobile, e— carrier ?


In respiratory electron transport, the protein ubiquinone (UQ), functionally equivalent to plastoquinone of chloroplast electron transport protein, acts as a mobile electron carrier. It transports electrons from complex I to cytochrome b-c1 complex.


Which of the following is the source of respiration?


R.Q. is less than one at the time of respiration of –


Respiratory quotient or R.Q is defined as the ratio of carbon dioxide evolved to oxygen taken in for respiratory break down of a substrate. The value of R.Q for oxidation of carbohydrates is unity and less than one for oxidation of fats and proteins. Thus if groundnut, which stores fats is used as respiratory substrate the value of R.Q will be less than one.


Number of ATP produced from one pyruvic acid during conversion to acetyl Co-A –

Solution: B is right becz when one pyruvic acid convert into acetyl co-A then one NADH2 produced, from which 3 ATP produced through ETS.

In succulent plants R.Q. is less than one because of


Respiratory quotient is defined as the ratio of carbon dioxide eliminated to that of oxygen consumed. Dark succulents undergo incomplete oxidation. When incomplete oxidation takes place, the value of R.Q. is zero. It is because during incomplete oxidation no carbon dioxide is released. Thus, the correct answer is option D.


The link between Glycolysis and Krebs cycle is


Aerobic respiration of glucose produces energy


 Succinyl Co-A is related to :


In eukaryotes, the citric acid cycle takes place in the matrix of the mitochondria, just like the conversion of pyruvate to acetyl CoA. In prokaryotes, these steps both take place in the cytoplasm. The citric acid cycle is a closed loop; the last part of the pathway reforms the molecule used in the first step. the CoA of succinyl CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP. In some cells,GDP—guanosine diphosphate—is used instead of ADP, forming GTP—guanosine triphosphate—as a product. The four-carbon molecule produced in this step is called succinate.


According to chemiosmotic theory of P. Mitchell (1978), ATPs are synthesised on membranes due to the :


A reduction of NADP to NADP.H2 is associated with


Breakdown of carbohydrates (glucose) takes place in the body by glycolysis followed by tricarboxylic acid cycle (Kreb's cycle) resulting in the energy in the form of ATP. Glucose can alternatively also undergo a different pathway to produce other products required by the cells. One of these alternate pathways is the pentose phosphate pathway or also called as hexose monophosphate pathway in which oxidation of glucose 6-phosphate takes place to produce pentoses. The fate of glucose whether to undergo glycolysis or the hexose monophosphate pathway is decided by the relative concentrations of NADP+ and NADPH. The phase starts with the oxidation of glucose 6-phosphate by the enzyme glucose 6-phosphate dehydrogenase to yield 6-phosphogluconolactone. This enzyme is an NADP dependent enzyme, where NADP+accepts an electron to form NADPH + H+.


Cut surfaces of fruits and vegetables often become dark because


Mineral activator needed for the enzymes Aconitase of TCA cycle is


Aconitase is an enzyme that catalyzes the reorganization of citrate into cis-aconitate releasing water. It is an iron-sulfur protein that functions both in TCA cycle as well as glyoxylate cycle. It is also known as citrate hydro lyase. The active site of enzyme consists of 21 amino acids and iron-sulfur cluster. 
Thus, the correct answer is option B.


An example of competitive inhibition of an enzyme is the inhibition of :

[AIIMS 2003]


Inhibitors, resemble with substrate molecules, join in the active site of the enzyme and inhibit the enzyme activity are called Competitive enzyme inhibitors.

Malonate is a competitive inhibitor of succinic dehydrogenase. The binding of succinic dehydrogenase to the substrate, succinate, is completely inhibited. Succinic dehydrogenase catalyzes the oxidation of succinate to fumarate in the Kreb cycle was an experiment demonstrated as an example of competitive inhibition.

So, the correct option is, 'succinic dehydrogenase by malonic acid'.


If the temperature is increased above 35°C


If the temperature is increased above35oC  rate of decline of photosynthesis will be earlier than decline of respiration. 
Factors that affect photosynthesis are the intensity of light, carbon dioxide concentration, and temperature.
The rate of photosynthesis is optimum at the optimum temperature ranging from 25oC to 35oC this is so because at temperatures around 0oC the enzymes stop working and at very high temperatures the enzymes get denatured. Hence if the temperature is increased to more than 35oC there will be a decline in the rate of photosynthesis due to denaturation of carbon fixing enzymes. Similarly, at very high temperatures, the rate of respiration also falls significantly. 


In hexose monophosphate shunt the number of CO2 molecules evolved is


Hexose monophosphate shunt is a secondary pathway for the metabolism of glucose in tissues other than skeletal muscles, in which five-carbon sugars are synthesized and NADPH is produced with the loss of CO2 in the cytoplasm outside the mitochondria, whereas there is no CO2 production in glycolysis.


Conversion of pyruvic acid into ethyl alcohol is mediated by –


Fermentation is a metabolic process that converts sugar to acids, gases, or alcohol and is carried out by a wide range of organisms. Yeast and other microorganisms ferment glucose to ethanol and CO2, rather than to lactate as in muscles of higher vertebrates. Glucose is converted to pyruvate by glycolysis, and the pyruvate is converted to ethanol and CO2 in a two-step process:
In the first step, pyruvate is decarboxylated in an irreversible reaction catalyzed by pyruvate decarboxylase. Pyruvate decarboxylase requires Mg2+ and has a tightly bound coenzyme, thiamine pyrophosphate.
In the second step, acetaldehyde is reduced to ethanol through the action of alcohol dehydrogenase, with the reducing power furnished by NADH derived from the dehydrogenation of glyceraldehyde 3-phosphate.
Ethanol and CO2 are thus the end products of ethanol fermentation, and the overall equation is as follows:
Glucose + 2ADP + 2Pi ----> 2 ethanol + 2 CO2 + 2 ATP + 2 H2O


The commonest living, which can respire in the absence of O2 is –


Option (b) is the correct answer.
Yeast performs anaerobic respiration i.e., in absence of oxygen. This respiration leads to fermentation process of yeast. Certain bacteria also performs anaerobic respiration.


The formation of Acetyl  Co-A from pyruvic acid is the result of its


Which of the following is link between carbohydrate and fat metabolism ?


Pyruvate dehydrogenase complex is used in converting –


The pyruvic acid generated in the glycolysis enters into the mitochondrial matrix, undergoes oxidative decarboxylation and forms active acetate in a coordinated series of reactions catalysed by the multienzyme complex. The reaction takes place in the presence of enzyme pyruvate dehydrogenase and several coenzymes including NAD+, coenzyme A, thiamine pyrophosphate and lipoic acid. The reaction occurs in 4 steps involving the conversion of pyruvic acid to acetyl coenzyme A. One molecule of carbon dioxide is released. The coenzyme NAD+ is reduced to NADH+H+ in the reaction. 

Thus, the correct answer is option D.


The first compound of TCA cycle is


TCA cycle is also known as Krebs cycle. TCA cycle stands for tricarboxylic acid cycle, which signifies that the first stable product is having three carboxylic groups. The first stable product is citric acid, which is a tricarboxylic acid. It is produced by the condensation of one molecule of acetyl CoA and one molecule of oxaloacetic acid.


Which of the following is coenzyme - II ?


Nicotinamide adenine dinucleotide phosphate, abbreviated NADP⁺ or, in older notation, TPN, is a cofactor used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent. It is the coenzyme - II


Where does the synthesis of enzyme occur in a cell


Protein synthesis occurs in cellular structures called ribosomes , found out-side the nucleus. The process by which genetic information is transferred from the nucleus to the ribosomes is called transcription. During transcription, a strand of ribonucleic acid (RNA) is synthesized.


Excess of ATP inhibits the enzyme –

Solution: It's A. Cuz Phosphofructokinases - 1(PFK-1)is one of the most important regulatory enzymes of glycolysis. It is an allosteric enzyme made up of 4 subunits and controlled by many activators n inhibitors. For example, a high ratio of ATP to ADP will inhibit PFK and glycolysis.

End product of glycolysis is


First reaction in pentose phosphate pathway is –


The breakdown of the simple sugar i.e. glucose in glycolysis provides the first 6- carbon molecule required for the pentose phosphate pathway. During the first step of glycolysis, glucose is transformed by the addition of a phosphate group, generating glucose-6-phosphate another 6- carbon molecule.


Oxidation of one molecule of glucose in aerobic respiration results in the production of


The glucose molecule is first broken down into two molecules of pyruvic acid through glycolysis. The glycolysis results in production of net 2 ATP molecules and 2 molecules of reduced coenzyme NADPH2​. The 2 molecules of  pyruvic acid are oxidatively decarboxylated by pyruvate dehydrogenase to yield two molecules of acetyl coenzyme and simultaneous production of two molecules of reduced coenzyme NADH2​​ one per conversion of pyruvic acid to acetyl CoA. The acetyl CoA enters Krebs cycle. Each moleucle of acetyl CoA that enters Krebs cycle generates 3 molecules of NADH2​​, 1 molecules of FADH2​​ and 1 molecule of GTP. Thus for two molecules of acetyl CoA from one glucose molecule, the net gain is 6 molecules of NADH2​ and 2 molecules of FADH2​ and 2 molecules of GTP. Assuming that one molecule of NADH2​​ is equivalent to 3 molecules of ATP and one molecule of FADH2​​ is equivalent to 2 molecules of ATP and one molecule of GTP is equivalent to one molecule of ATP. The net gain from entire aerobic breakdown of glucose comes out to be 38 molecules of ATP. 

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