31 Years NEET Previous Year Questions: Respiration in Plants - 1 - NEET MCQ

Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while that of one molecule of FADH₂ produces 2 molecules of ATP.

During Krebs' or citric acid cycle, succinyl-CoA is acted upon by enzyme succinyl-CoA synthetase to form succinate (a 4C compound). The reaction releases sufficient energy to form ATP (in plants) or GTP (in animals) by substrate-level phosphorylation. GTP can then be used to form ATP.

Glucose is phosphorylated to glucose-6- phosphate by ATP in presence of enzyme hexokinase and Mg²⁺.

 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.

Carbohydrates are usually first converted into glucose before they are used for respiration. Fats are broken down into glycerol and fatty acids first. If fatty acids were to be respired they would first be degraded to acetyl CoA and enter the pathway. Glycerol would enter the pathway after being converted to 3-phosphoglyceraldehyde (PGAL). The proteins are degraded by proteases to individual amino acids (after deamination) and depending on their structure enter the pathway within the Krebs’ cycle or as pyruvate or acetyl CoA. Thus, acetyl CoA is the common metabolite of all the three (carbohydrates, proteins and fats).

The energy releasing metabolic process in which substrate is oxidised without 
an external electron acceptor is called fermentation.

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

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

In germinating seeds, fatty acids are degraded exclusively in the glyoxysomes. Glyoxylate cycle occurs in tissues rich in fats, such as those of germinating seeds; the enzymes involved in the cycle, which have not been found in mammals, are contained in organelles called glyoxysomes

Fermentation is an anaerobic pathway which takes place in certain bacteria and fungi which do not involve electron transport chain. In this process, substrate level phosphorylation takes place in glycolysis producing 2 ATP molecules. 

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.

Succinate dehydrogenase enzyme is present on inner membrane of mitochondria and catalysed the oxidation of succinate to fumarate.

Succinate dehydrogenase enzyme is present on inner membrane of mitochondria and catalysed the oxidation of succinate to fumarate.

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.

12 kcal of energy present in one molecule of ATP & on oxidation of one mole of glucose into CO₂ and H₂O energy released in 686 kcal. So no. of ATP which can store this energy would be = 57.1 = 57 ATPs.

In glycolysis 4 ATP and 2NADH₂ molecules are formed. These 2NADH₂  molecules go to electron transport chain. In oxidative decarboxylation no ATP molecule is formed but two molecules of 2NADH₂  are formed from two molecules of pyruvate. These two NADH₂go to electron transport chain. In Kreb's cycle 2 ATP, 6NADH₂and 2FADH₂ molecules are formed from two molecule of acetyl Co-A. These NADH2 and 2FADH₂  go to electron transport chain. In electron transport chain all 2NADH2   and 2FADH2  pass to electron carriers and yield 3 ATP and 2 ATP molecules per 2NADH2   and 2FADH2  respectively. Thus,  4 ATP are formed in glycolysis, 2 ATP in Krebs cycle and 34 ATP from electron transport chain. 40 ATP and 2 ATP molecules are used during glycolysis. So, net gain of ATP molecules during one complete oxidation of a glucose molecule is 38 ATP.

So, the correct answer is 'Electron transport chain'.

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.

ATP is the energy currency in all cells. Glyceraldehyde 3 - phosphate is reduced during glycolysis. Molecular oxygen is the terminal electron acceptor in ETS.

TCA cycle is so called because the first stable product formed is a tricarboxylic acid molecule that is citric acid. Hence the name citric acid cycle . It is also called the Krebs cycle.

Photophosphorylation refers to addition of phosphate in the presence of light.

Lignin is a complex polymer of phenylpropane units, which are crosslinked to each other with a variety of different chemical bonds.

In alcohol fermentation triose phosphate is the electron donor while acetaldehyde is the electron acceptor.

38 ATP molecules are produced by aerobic oxidation of glucose.

During aerobic respiration, 38 ATP molecules are gained. If specifically aerobic respiration in eukaryotes is asked, then the answer would be 36 ATP because 2 ATP molecules are produced by which accepts the form 2 NADH molecules produced in glycolysis

The energy yield during aerobic respiration (36 ATP) is 18 times of that  during anaerobic respiration ( 2 ATP).

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. 

In the conversion of succinyl Co A to succinic acid, energy liberated during hydrolysis of succinyl CoA is used in synthesis of  GTP. For the conversion of alfa-ketoglutarate to succinyl CoA, NAD+ and CoA are required. Conversion of fumaric acid to malic acid involves simple hydration. FAD participates in conversion of succinic acid to fumaric acid.

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.

Fermentation is referred to as the decomposition of organic compounds, anaerobically by enzymes yielding alcohol, organic acids; gases etc.

The enzyme involved in Krebs cycle are localized in the mitochondrial matrix.

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.