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All questions of Respiration in Plants for NEET Exam

Net gain of ATP molecules during aerobic respiration is [1999]
a)38 molecules
b)36 molecules
c)40 molecules
d)48 molecules
Correct answer is option 'A'. Can you explain this answer?

Rohan Unni answered
38 molecules of ATP produced during aerobic respiration. Of these 2 ATP are used in link reaction. Hence net gain is of 36 ATP. 
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End product of glycolysis is [1990]
  • a)
    acetyl CoA
  • b)
    pyruvic Acid
  • c)
    glucose 1-phosphate
  • d)
    fructose 1-phosphate
Correct answer is option 'B'. Can you explain this answer?

Shivani Tiwari answered
Pyruvic acid is formed as an end product of glycolysis, a process that breaks down glucose (a six-carbon molecule) into two molecules of pyruvate (a three-carbon molecule) and simultaneously yields a small net gain of the universal energy storage molecule adenosine triphosphate (ATP), used to power cellular function.

The energy-releasing process in which the substrate is oxidised without an external electron acceptor is called [2008]
  • a)
    fermentation
  • b)
    photorespiration
  • c)
    aerobic respiration
  • d)
    glycolysis 
Correct answer is option 'D'. Can you explain this answer?

Dipika Das answered
Glycolysis takes place in all body cells and is of two types- (a) Anaerobic glycolysis-From glycogen or glucose to lactic acid in muscles. (b) Aerobic glycolysis- From glycogen or glucose to pyruvic acid (all cells of body) 

Incomplete oxidation of glucose into pyruvic acid with several intermediate steps is known as[1988]
  • a)
    TCA-pathway
  • b)
    glycolysis
  • c)
    HMS-pathway
  • d)
    Krebs cycle
Correct answer is option 'B'. Can you explain this answer?

Maheshwar Saini answered
Glycolysis involves the process of partial oxidation of glucose or similar hexose sugar into two molecules of pyruvic acid through a series of ten enzyme mediated reactions. It occurs in cytoplasm.

Site of respiration in bacteria is [1997]
  • a)
    episome
  • b)
    ribosome
  • c)
    mesosome
  • d)
    microsome
Correct answer is option 'C'. Can you explain this answer?

Rhea Sarkar answered
Mesosome.
Mesosomes are the invaginations of the plasma membrane that can form into vesicles. They are found to be present in both gram-positive and gram-negative bacteria. Mesosomes may play a role in cell wall formation during cell division and/or chromosome replication and distribution and/or electron transfer systems of respiration. 

Out of 38 ATP molecules produced per glucose, 32 ATP molecules are formed from NADH/FADH2 in [1993]
  • a)
    respiratory chain
  • b)
    Krebs cycle
  • c)
    oxidative decarboxylation
  • d)
    EMP
Correct answer is option 'A'. Can you explain this answer?

Anjali Iyer answered
The electron transport chain along with oxidative phosphorylation involves the synthesis of energy-rich ATP molecules with the help of energy released during the oxidation of reduced coenzymes (NADH2 and FADH2) formed during glycolysis and the Krebs cycle. A total of 10 NADH2 and 2 FADH2 molecules are produced during aerobic respiration. They help in the formation of 32 ATP molecules.

In glycolysis, during oxidation electrons are removed by [2004]
  • a)
    ATP
  • b)
    glyceraldehyde-3-phosphate
  • c)
    NAD+
  • d)
    molecular oxygen
Correct answer is option 'C'. Can you explain this answer?

Mahesh Saini answered
During glycolysis, NAD (Nicotinamide adenine dinucleotide) removes electrons from 1, 3-diphos-phoglyceric acid using diphospho- glycrealdehyde dehydrogenase. NAD changes to NADR, and this is either utilized as such in anaerobic respiration or in the presence of oxygen.

How many ATP molecules could maximally be generated from one molecule of glucose, if the complete oxidation of one mole of glucose to CO2 and H2O yields 686 kcal and the useful chemical energy available in the high energy phosphate bond of one mole of ATP is 12 kcal ? [2006]
  • a)
    Thirty
  • b)
    Fifty -seven
  • c)
    One
  • d)
    Two
Correct answer is option 'B'. Can you explain this answer?

Madhavan Verma answered
If one mole of glucose yields a total energy of 686 Kcal after complete oxidation and it is given that the chemical energy in phosphate bonds of one mole of ATP is 12 Kcal. Then the number of molecules that could be generated from one glucose molecule could be calculated by dividing the total energy by energy of one mole of ATP i.e. 686�12. This gives an answer of 57 ATP.

Oxidative phosphorylation is production of
  • a)
    ATP in photosynthesis [1992]
  • b)
    NADPH in photosynthesis
  • c)
    ATP in respiration
  • d)
    NADH in respiration
Correct answer is option 'B'. Can you explain this answer?

Ashish Tiwari answered
Overview: oxidative phosphorylation
Simple diagram of the electron transport chain. The electron transport chain is a series of proteins embedded in the inner mitochondrial membrane.
In the matrix, NADH and FADH2 deposit their electrons in the chain (at the first and second complexes of the chain, respectively).
The energetically "downhill" movement of electrons through the chain causes pumping of protons into the intermembrane space by the first, third, and fourth complexes.
Finally, the electrons are passed to oxygen, which accepts them along with protons to form water.
The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP. Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP.
The electron transport chain is a series of proteins and organic molecules found in the inner membrane of the mitochondria. Electrons are passed from one member of the transport chain to another in a series of redox reactions. Energy released in these reactions is captured as a proton gradient, which is then used to make ATP in a process called chemiosmosis. Together, the electron transport chain and chemiosmosis make up oxidative phosphorylation. The key steps of this process, shown in simplified form in the diagram above.

Aerobic respiratory pathway is appropriately termed: [2009]
  • a)
    parabolic
  • b)
    amphibolic
  • c)
    anabolic
  • d)
    catabolic
Correct answer is option 'B'. Can you explain this answer?

Shruti Chauhan answered
All energy-releasing pathways whether aerobic (requiring oxygen) or anaerobic (not requiring oxygen) begin with a pathway called glycolysis, which occurs in the cytoplasm (cytosol). Aerobic respiratory pathway is appropriately termed amphibolic. Aerobic respiration is the main energy-releasing pathway leading to ATP formation. It occurs in the mitochondria. Aerobic respiration yields thirty-six ATP

Life without air would be [1993]
  • a)
    reductional
  • b)
    free from oxidative damage
  • c)
    impossible
  • d)
    anaerobic
Correct answer is option 'D'. Can you explain this answer?

Rajat Rai answered
Air means O2 here;Actually when we talk abt Aerobic or Anaerobic process we talk in context with intracellular rxns,We need O2 for breakdown of food hence We are Aerobic whereas those organisms which Breakdown their food By means of anything but not O2 are anaerobes! This is wht Comes into my mind when I hear these terms!

Chemiosmotic theory of ATP synthesis in the chloroplasts and mitochondria is based on:[2005]
  • a)
    membrane potential
  • b)
    accumulation of Na ions
  • c)
    accumulation of K ions
  • d)
    proton gradient
Correct answer is option 'D'. Can you explain this answer?

Aman Sharma answered
The enzyme responsible for oxidative phosphorylation is ATP synthase. ATP synthase is located in the F1 component of F0 – F1 or elementary particles. ATP synthase becomes active in ATP formation only where there is a proton gradient having higher concentration of H+ or protons on the F0 side as compared to F1 side. Increased proton concentration is produced in the outer chamber of outer surface of inner mitochondrial memberane by the pushing of protons with the help of energy liberated by passage of electrons from one carrier to another.

Maximum amount of energy/ATP is liberated on oxidation of [1994]
  • a)
    fats
  • b)
    proteins
  • c)
    starch
  • d)
    vitamins
Correct answer is option 'A'. Can you explain this answer?

Deepak Joshi answered
Fats are used as respiratory substrates by a number of organisms because they contain more energy as compared to carbohydrates.

Respiratory substrate yielding maximum number of ATP molecule is [1994]
  • a)
    ketogenic amino acids
  • b)
    glucose
  • c)
    amylose
  • d)
    glycogen
Correct answer is option 'B'. Can you explain this answer?

Dipanjan Mehta answered
Firstly, amylose and glycogen are converted to glucose. Deamination of ketogenic amino acids occur and these enter respiratory catabolism as intermediates.

End products of aerobic respiration are [1992]
  • a)
    sugar and oxygen
  • b)
    water and energy
  • c)
    carbon dioxide, water and energy
  • d)
    carbon dioxide and energy
Correct answer is option 'C'. Can you explain this answer?

Surbhi Das answered
The end products of aerobic respiration are 38 atp of energy, carbon dioxide and water while of anaerobic respiration is ethanol and 2atp of energy.

End product of citric acid/Krebs cycle is [1993]
  • a)
    citric acid
  • b)
    lactic acid
  • c)
    pyruvic acid
  • d)
    CO2 + H2O
Correct answer is option 'D'. Can you explain this answer?

Shivani Rane answered
The end product of glycolysis is pyruvic acid whereas acetyl CoA is the connecting link between glycolysis and Krebs' cycle. The TCA cycle was first described by Krebs, 1937 as a cyclic process in which acetyl coA is oxidised to CO2 and water. Acetyl CoA combines with oxalo acetic acid to form citric acid. After a series of cyclic reactions OAA is recycled back.

Which of the metabolites is common to respiration mediated breakdown of fats, carbohydrates and proteins? [NEET 2013]
  • a)
    Fructose 1, 6 - bisphosphate
  • b)
    Pyruvic acid
  • c)
    Acetyl CoA
  • d)
    Glucose - 6 - phosphate
Correct answer is option 'C'. Can you explain this answer?

Aman Sharma answered
Acetyl CoA is common to respiration mediated breakdown of fats, carbohydrates and proteins. Fats are broken down to fatty acid and glycerol and again fatty acid degraded to acetyl Co - A . Protein first degraded by proteases to indiviual amino acids which deaminated to pyruric acid and further decarboxylised to acetyl Co- A

The energy - releasing metabolic process in which substrate is oxidised without an external electron acceptor is called: [2010]
  • a)
    glycolysis
  • b)
    fermentation
  • c)
    aerobic respiration
  • d)
    photorespiration
Correct answer is option 'B'. Can you explain this answer?

Palak Khanna answered
In fermentation, the incomplete oxidation of glucose is achieved under anaerobic conditions by a set of reactions, where pyruvic acid is converted to CO2 and ethanol. The enzyme pyruvic acid, decarboxylase and alcohol dehydrogenase catalyse these reactions. In animals cells also, like muscles during exercise, where oxygen is inadequate for cellular respiration, pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH + H+, which is reoxidized to NAD+, in both the processes. 

In germinating seeds fatty acids are degraded exclusively in the [2008]
  • a)
    proplastids
  • b)
    glyoxysomes
  • c)
    peroxisomes
  • d)
    mitochondria 
Correct answer is option 'B'. Can you explain this answer?

Dipanjan Chawla answered
Glyoxysomes are found to occur in the cells of yeast, Neurospora and oil rich seeds of many higher plants. During germination of oily seeds, the stored lipid molecules of sphaerosomes are hydrolysed by the enzyme lipase to glycerol and fatty acids. The long chain fatty acids are then broken down by successive removal of two carbon fragments in the process of (
β
-oxidation).

Peroxisomes are present in all photosynthetic cells of higher plants in etiolated leaf tissue. It is the site of hydrogen peroxide metabolism and glycolate cycle.

Mitochondria is the site of aerobic respiration in eukaryotic cell. It is called power house of the cell.

During the development of chioroplast the first structure to appear is so called proplastid, which has a double membrane.

The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (ATP) is formed because: [2008]
  • a)
    high energy bonds are formed in mitochondrial proteins
  • b)
    ADP is pumped out of the matrix into the intermembrane space 
  • c)
    a proton gradient forms across the inner membrane
  • d)
    there is a change in the permeability of the inner mitochondrial membrane toward adenosine diphosphate (ADP)
Correct answer is option 'C'. Can you explain this answer?

Kajal Bose answered
Chemiosmotic theory postulated by the British biochemist Peter Mitchell (1920-22) to explain the formation of ATP in the mitochondrial electron transport chain. As electrons are transferred along the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported into the space between the inner and outer mitochondrial membranes, which thus contains a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, through which protons move back into the matrix

The number of substrate level phosphorylations in one turn of citric acid cycle is :   [2020]
  • a)
    Two
  • b)
    Three
  • c)
    Zero
  • d)
    One
Correct answer is option 'D'. Can you explain this answer?

Abhijeet Iyer answered
In one turn of the citric acid cycle, also known as the Krebs cycle or the tricarboxylic acid (TCA) cycle, there is only one substrate level phosphorylation.

What is Substrate Level Phosphorylation?
Substrate level phosphorylation is a metabolic process in which a phosphate group is transferred from a substrate molecule to ADP, resulting in the formation of ATP. This process occurs directly in the metabolic pathway, unlike oxidative phosphorylation which occurs in the electron transport chain.

The Citric Acid Cycle and Substrate Level Phosphorylation
The citric acid cycle is a series of biochemical reactions that occur in the mitochondria, and it plays a crucial role in aerobic respiration. It is an eight-step cycle that oxidizes acetyl-CoA, a product of glycolysis, to generate ATP and other energy-rich molecules.

Steps of the Citric Acid Cycle
1. Step 1: Formation of Citrate: Acetyl-CoA reacts with oxaloacetate to form citrate, a six-carbon molecule.
2. Step 2: Isomerization: Citrate is converted into its isomer, isocitrate.
3. Step 3: Oxidative Decarboxylation: Isocitrate is oxidized and decarboxylated to form alpha-ketoglutarate, which releases one molecule of CO2 and generates one molecule of NADH.
4. Step 4: Oxidative Decarboxylation: Alpha-ketoglutarate undergoes another oxidative decarboxylation reaction, producing another molecule of NADH and one molecule of CO2. It is converted into succinyl-CoA.
5. Step 5: Substrate Level Phosphorylation: Succinyl-CoA is converted into succinate, and in this step, substrate level phosphorylation occurs. A phosphate group is transferred from succinyl-CoA to ADP, forming one molecule of ATP and succinate.
6. Step 6: Dehydrogenation: Succinate is oxidized to form fumarate, generating one molecule of FADH2.
7. Step 7: Hydration: Fumarate is hydrated to form malate.
8. Step 8: Dehydrogenation: Malate is oxidized to form oxaloacetate, generating one molecule of NADH.

Conclusion:
In the citric acid cycle, there is only one step (Step 5) where substrate level phosphorylation occurs. This step involves the transfer of a phosphate group from succinyl-CoA to ADP, forming ATP. Therefore, the correct answer is d) One.

In animal cells, the first stage of glucose breakdown is [1994]
  • a)
    Krebs cycle
  • b)
    glycolysis
  • c)
    oxidative phosphorylation
  • d)
    E.T.C
Correct answer is option 'B'. Can you explain this answer?

Prisha Singh answered
The initial breakdown of glucose occurs in the cell cytoplasm. This is an anaerobic reaction of cellular respiration, meaning that it does not require oxygen. Here, in a series of eight individual reactions, a six-carbon glucose molecule is metabolized using two adenosine triphosphate (ATP) molecules to form two three-carbon pyruvate molecules, two H2O (water) molecules and four ATP molecules for a net gain of two ATP molecules. ATP is a primary source of energy in human metabolism.

The enzymes hexokinase which catalyses glucose to glucose-6-phosphate in glycolysis is inhibited by glucose-6-phosphate. This is an example of [1996]
  • a)
    competitive inhibition
  • b)
    non-competitive inhibition
  • c)
    feedback allosteric inhibition
  • d)
    positive feedback.
Correct answer is option 'C'. Can you explain this answer?

Arindam Khanna answered
Competitive inhibition is the reversible inhibition of enzyme activity due to presence of substrate analogues. Non competitive inhibition is the reduction of enzyme activity by a factor that has no real structural similarity with the substrate. Allosteric inhibition  is reversible  noncompetitive inhibition occurring in case of allosteric enzymes. Herein the inhibitors are the products or intermediates of reactions catalyzed by the enzymes. Hence it is also called end product inhibition or feedback inhibition.

Maximum usable energy per mol of glucose metabolised will be generated during [1999]
  • a)
    aerobic respiration by germinating seeds
  • b)
    production of methanol by enteric bacteria
  • c)
    fermentation into ethanol by yeast
  • d)
    glycolysis in the skeletal muscle of a sprinter performing a hundred metre dash
Correct answer is option 'A'. Can you explain this answer?

Yash Saha answered
The germinating seeds undergo aerobic respiration as they use the oxygen available inside the conical flask. As whole of the oxygen is used up by the germinating seeds, the pressure inside the flask is decreased. Hence, consequently the mercury level rises in the far end of the bent glass tube.

This level reaches only a height of 15 cm in the glass tube. As this level is about one-fifth the air. As oxygen constitutes one fifth of total composition, it is reasonable to infer that the seeds have used this gas of the air in respiration.

During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded ? [2003]
  • a)
    Cellulose
  • b)
    Lipids
  • c)
    Lignin
  • d)
    Hemi-cellulose
Correct answer is option 'C'. Can you explain this answer?

Subham Chavan answered
During bio-gas formation, digestion of cellulose is slow (rate-limiting) and most of the lignin ls not decomposed. After cellulose lignin is the most abundant plant polymer. It forms 20 to 30% of the wood of the tree. Lignin is a complex polymeric molecule, made up of phenyl propanoid units. Cellulose rs a large chained polymer of giucose molecules which are linked with each other by glycosidic bonds. Hemicellulose are branched polymers of glucose, xylose, galactose, mannose and arabinose.

The mechanism of ATP formation both in chloroplast and mitochondria is explained by[1997]
  • a)
    relay pump theory of Godlewski
  • b)
    Munch’s pressure/ mass flow model
  • c)
    chemiosmotic theory of Mitchell
  • d)
    Cholondy-Went’s Model
Correct answer is option 'C'. Can you explain this answer?

Diya Datta answered
According to the chemiosmotic theory the energy liberated during electron transport performs the osmotic work of  accumulating H+ ions, conserving energy in building a proton gradient, which is used to build ATP from ADP and inorganic phosphate.

Respiratory quotient (R.Q.) for fatty acid is [1995]
  • a)
    > 1
  • b)
    < 1
  • c)
    1
  • d)
    0
Correct answer is option 'B'. Can you explain this answer?

Rohan Unni answered
Respiratory quotient (R.Q.) is defined as the ratio of the molecules of carbon dioxide given out to the number of oxygen molecules taken in during respiration. Its value for fatty acids is always less than unity.

Oxidative phosphorylation involves simultaneous oxidation and phosphorylation to finally form [1996]
  • a)
    pyruvate
  • b)
    NADP
  • c)
    DPN
  • d)
    ATP
Correct answer is option 'D'. Can you explain this answer?

Arindam Khanna answered
Oxidative phosphorylation is the synthesis of energy rich ATP from ADP and  inorganic phosphate, that is connected to oxidation of reduced coenzymes produced in cellular  respiration.

The overall goal of glycolysis, krebs cycle and the electron transport system is the formation of[2007]
  • a)
    ATP in one large oxidation reaction
  • b)
    sugars
  • c)
    nucleic acids
  • d)
    ATP in small stepwise units.
Correct answer is option 'D'. Can you explain this answer?

Pallabi Reddy answered
Glycolysis, Krebs cycle and electron transport system, they all give ATP  which is the main energy currency of our body. Glycosis takes place in cytoplasm, Krebs cycle also in cytoplasm and ETS takes place in the mitochondria.

The three boxes in this diagram represents the three major  biosynthetic pathways in aerobic respiration. Arrows represents net reactants or products. [NEET 2013]
Arrows numbered 4, 8 and 12 can all be :
  • a)
    ATP
  • b)
    H2O
  • c)
    FAD+ or FADH2
  • d)
    NADH
Correct answer is option 'A'. Can you explain this answer?

Ruchi Chopra answered
 In a given diagram of aerobic respiration – pathway A is glycolysis, pathway B is kreb’s cycle and pathway C is ETS , thus  4, 8 & 12 are ATP. ATP act as energy currency. The energy trapped in form of ATP and it broken down whenever and wherever it needs to be utilised.

The bacterium (Clostridium botulinum) that  causes botulism is [2006]
  • a)
    an obligate anaerobe
  • b)
    an facultative aerobe
  • c)
    an obligate aerobe
  • d)
    a facultative anaerobe
Correct answer is option 'A'. Can you explain this answer?

Rohan Unni answered
Clostridium botulinum is an obligate anaerobe i.e. it normally lives in the absence of oxygen. Facultative anaerobes are those who generally live in oxygen but may live without oxygen in suitable medium. Obligate aerobes can only live in the presence of oxygen while facultative aerobes generally live in oxygen but can also live without oxygen.

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