Respiration in Plants MCQ Quiz in मल्याळम - Objective Question with Answer for Respiration in Plants - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is: Both Assertion and Reason are true, and Reason is the correct explanation for Assertion.

Explanation:

• Assertion: FADH₂ generates fewer ATP molecules than NADH during oxidative phosphorylation.
  • This statement is true. NADH typically yields about 2.5 ATP molecules per molecule, while FADH₂ yields about 1.5 ATP molecules per molecule.
• Reason: FADH₂ donates electrons to Complex II, bypassing Complex I of the electron transport chain.
  • This statement is also true. FADH₂ enters the electron transport chain at Complex II, rather than Complex I, which is the entry point for NADH.
  • As a result, electrons from FADH₂ skip the proton pumping action of Complex I. Therefore, fewer protons are pumped into the intermembrane space compared to electrons donated by NADH.
  • This results in a smaller proton gradient and less ATP production.
• The Reason correctly explains the Assertion because the fewer ATP molecules generated by FADH₂ are directly due to its entry point at Complex II and the bypassing of Complex I, thereby reducing proton pumping and ATP synthesis.

The correct answer is Oxygen

Explanation:

• Oxidative phosphorylation is the process of ATP production that occurs in the mitochondria, using the electron transport chain (ETC) and chemiosmosis.
• Electrons are transferred through a series of protein complexes and other molecules in the inner mitochondrial membrane.
• During this process, electrons are passed from electron donors like NADH and FADH₂ to various acceptors via the ETC.
• At the end of the electron transport chain, the final acceptor of electrons is molecular oxygen (O₂). It combines with electrons and protons (H⁺) to form water (H₂O).

The correct answer is A- Fructose-6-phosphate, B- Fructose1,6-bisphosphate, C- Glyceraldehyde-3-phosphate, D-Triose bisphosphate

Concept:

• Glycolysis is the process in which glucose is broken down to produce energy in the form of ATP.
• ATP is synthesized during glycolysis in two main steps.
• The first step is when 1,3-bisphosphoglycerate (1,3-BPG) is converted into 3-phosphoglycerate (3PGA) by the enzyme phosphoglycerate kinase, which results in the production of ATP.
• The second step where ATP is synthesized occurs when phosphoenolpyruvate (PEP) is converted into pyruvate.
• Conversion of glucose into glucose-6-phosphate requires ATP and does not generate ATP.

Fig: Steps in Glycolysis

The correct answer is amphibolic

Concept:

• The respiratory pathway is a metabolic pathway that involves the breakdown of organic molecules to produce energy.
• It is considered an amphibolic pathway because it serves both catabolic and anabolic functions.
• Catabolic: The pathway breaks down molecules like glucose to produce ATP, which is a catabolic process.
• Anabolic: The intermediates produced during respiration can also be used as precursors for the synthesis of other biomolecules, which is an anabolic process.
• Because the respiratory pathway involves both breakdown and synthesis, it is referred to as amphibolic.

Explanation:

• Amphibolic: The respiratory pathway is termed amphibolic because it integrates both catabolic and anabolic processes.
• Catabolic: While respiration has catabolic aspects, describing it only as catabolic overlooks its anabolic role.
• Anabolic: Respiration isn't purely anabolic, as it primarily breaks down molecules.
• Endergonic: Respiration is not endergonic; it is an exergonic process that releases energy.

The correct sequence is Cyt b, c, a, a₃

Explanation:

• The electron transport chain in cellular respiration involves a series of electron carriers. The correct sequence through which electrons are passed during ATP synthesis in mitochondria is from Cytochrome b (Cyt b) to Cytochrome c (Cyt c), then to Cytochrome a (Cyt a), and finally to Cytochrome a₃ (Cyt a₃). This sequence is crucial for the efficient production of ATP through oxidative phosphorylation.
• The electron transport chain is a series of complexes that transfer electrons from electron donors to electron acceptors via redox reactions. This process is coupled with the transfer of protons (H⁺ ions) across the mitochondrial membrane, creating a proton gradient that drives the synthesis of ATP.
• The correct sequence of electron acceptors is critical for the gradient's establishment and the efficient production of ATP. Any deviation from this sequence disrupts the process and reduces the efficiency of energy production in cells.

Key Points

• Substrate level phosphorylation is defined as the process of formation of ATP by the physical addition of phosphate group to ADP.
• It occurs during both glycolysis and Kreb's cycle. 
• Oxidative phosphorylation refers to the oxidation of reducing substances NADH and FADH₂ by the transfer of their electrons through an electron transport chain to oxygen, which releases energy for the synthesis of ATP by ADP and Pi.
• In oxidative phosphorylation, ATP produces by chemiosmosis and it takes place in the inner membrane of mitochondria.
• EMP pathway is commonly known as glycolysis.
• It takes place in the cytoplasm of all living cells, both aerobically as well as anaerobically.

Explanation:

• In the EMP pathway, 4 ATP molecules are formed as a result of substrate-level phosphorylation. 
  • When a phosphate group is lost, 1,3-diphosphoglycerate transforms into 3-phosphoglycerate, forming the first two ATP molecules.
  • In the final stage of glycolysis, 2-phosphoenol pyruvic acid transforms into pyruvic acid by transferring its high-energy phosphate bond from ADP and forming two more ATP.
• In the EMP pathway, there are 6 ATP molecules are formed during oxidative phosphorylation.
  • Glycolysis proceeds by phosphorylation of glyceraldehyde-3-phosphate to 1,3- diphosphoglyceric acid at carbon 1 by inorganic phosphoric acid and simultaneously oxidation takes by dehydrogenation.
  • NAD-dependent glyceraldehyde-3-phosphate dehydrogenase enzyme is responsible for oxidation.
  • The resulting hydrogen is carried by NAD as NADH + H⁺.
  • Forms six ATP molecules in this step.

Additional Information

• During Kreb's cycle, succinyl coenzyme A transfers its high energy to a phosphate group, which combines GDP/ADP to produce GTP/ATP and proceeds to phosphorylate two ATP molecules at the substrate level.
• In oxidative phosphorylation, the final electron acceptor is oxygen, and the resulting proton gradient provides energy for the ATP synthase enzyme to produce ATP.

Hence, the correct option is (3) 4 and 6.

Concept:

• The respiratory quotient is also known as the respiratory ratio and is denoted by RQ.
• It is defined as the volume of carbon dioxide released over the volume of oxygen absorbed during the process of respiration.
• \({RQ} = {Volume \space of \space CO_2 \space released \over Volume \space of \space O_2 \space absorbed}\)​

Important Points

• The respiratory quotient depends on the type of respiratory substrate used during respiration, the amount of oxygen present in the respiratory substrate, the extent to which respiratory substrate is broken down.

Carbohydrates -

• When carbohydrate is the substrate, following three cases can be there:

1. In aerobic respiration:
   • C₆H₁₂O₆+ 6O₂ → 6CO₂ + 6H₂O
   • Equal amounts of carbon dioxide and oxygen are evolved and consumed, respectively. So, RQ = 1.
2. In anaerobic respiration:
   • As this process occurs in absence of oxygen, so total amount of oxygen consumed/absorbed is 0 and only carbon dioxide production is there.
   • RQ = ∞
3. When Carbohydrate is incompletely oxidized, there is no production of CO₂. RQ = 0

​Proteins -

• RQ for protein is approximately 0.8.
• We can consider the reaction for albumin metabolism here,

C₇₂H₁₁₂N₁₈O₂₂S + 77 O₂ → 63 CO₂ + 38 H₂O + SO₃ + 9 CO(NH₂)₂

• \({RQ} = {63 \over 77} = 0.8\)

Fats -

• Fats are not completely oxidized so, RQ is 0.7.
• We can consider the chemical equation of triglyceride here,

C₅₅H₁₀₄O₆ + 78 O₂ → 55 CO₂ + 52 H₂O

• \({RQ} = {55 \over 78} = 0.7\)

​Organic acids -

• Organic acids (malic acid , tartaric acid, oxalic acid) contain a higher amount of oxygen in them, so they require less O₂ for respiration.
• This makes the respiratory quotient to be more than 1.

C₄H₆O₅ (Malic acid) + 3 O₂ → 4 CO₂ + 3 H₂O + Energy

• \({RQ} = {4 \over 3} = 1.33\)

​​Explanation:

• A RQ of 0.7 can be achieved when fats or lipids are used as substrate.
• On the other hand, incomplete oxidation of carbohydrates will result in a RQ = 0.
• Thus, carbohydrates and lipids can together give a RQ of 0.7.
• For all the other given combinations, the RQ will be more than 0.7.

Therefore, the correct answer is option 4 - (b) + (d).

Concept:

• Cellular respiration can be defined as the metabolic process by which complex organic substances are broken down into simple products. 
• During this process, energy is released that is stored in energy-carrying biomolecules called ATP. This energy is later utilized to carry out other metabolic activities.
• In eukaryotic cells, mitochondria play an important role in ATP synthesis.
• The enzymes required for ATP synthesis are present in the mitochondria.
• However, the generation of ATP also takes place in certain processes without involving mitochondria such as in glycolysis.

Explanation:

Option 1: Krebs cycle - INCORRECT

• ​Krebs cycle also known as the TCA cycle is part of aerobic respiration.
• It provides energy to cells in the form of ATP.
• It takes place in the matrix of mitochondria.

Option 2: Electron Transport Chain - INCORRECT

• Electron Transport Chain is the third step during aerobic respiration and involves the formation of the water molecule and ATP.
• ETS takes place in the inner mitochondrial membrane.
• NADH₂ and FADH₂ produced during the initial steps of aerobic respiration - glycolysis, connecting link reaction, and Kreb's cycle- are oxidized in ETC with the help of various electron carriers and enzymes.

Option 3: Substrate-level Phosphorylation - CORRECT

• ​Substrate-level Phosphorylation is a chemical reaction in which ATP is synthesized by direct transfer of phosphate group from an intermediate molecule to ADP.
• Substrate-level Phosphorylation is seen during the process of glycolysis.
• Glycolysis is the first step in both aerobic and anaerobic respiration.
• It takes place in the cytoplasm without the use of oxygen.
• During glycolysis 2 ATP molecules are produced.
• These ATP molecules are formed without the involvement of mitochondria.

Option 4: Photorespiration - INCORRECT

• ​Photorespiration occurs in photosynthetic plants.
• Photorespiration can be defined as a light-dependent process in which the photosynthetic organs of a plant utilize oxygen and release carbon dioxide.
• Photorespiration is considered to be a wasteful process. This is because 25% of photosynthetically fixed carbon dioxide is lost in this process.
• It takes place in several organelles - chloroplast, peroxisome and mitochondria.
• At the end of the photorespiration CO₂ and ammonia are released. No ATP is produced in this process.

So the correct answer is option 3 (Substrate-level phosphorylation).

Concept:

• Respiration is a catabolic process that involves the production of energy-rich molecules called ATP.
• Respiration can be defined as a process by which complex organic molecules are oxidized to simpler molecules like CO₂ and H₂O with the release of energy.
• This energy is used up by the organism to carry out other metabolic activities.
• There are two types of respiration - Aerobic respiration and Anaerobic respiration

Aerobic respiration: 

​It occurs in the presence of oxygen and there is complete oxidation of the organic molecules.   

C₆H₁₂O₆ + 6O₂ →  6CO₂ + 6H₂O + ATP 

• Steps involved: Glycolysis, Krebs cycle, and Electron Transport System (ETS)

Anaerobic respiration:

It occurs in the absence of oxygen and there is incomplete oxidation of organic molecules.       

C6H12O6 →  2C₂H₅OH + 2CO₂ + ATP 

Steps involved: Glycolysis and Fermentation

Explanation:

Electron Transport System (ETS):

• ETS is the third step during aerobic respiration. It involves the formation of water molecules and energy molecules (ATP).
• ETS takes place in the inner mitochondrial membrane.
• NADH₂ and FADH₂ produced during the initial steps of aerobic respiration - glycolysis, connecting link reaction, and Krebs cycle- are oxidized in ETS with the help of various electron carriers and enzymes.
• The energy-rich molecules - ATP - are synthesized with the help of energy released during the oxidation of NADH₂ and FADH_2. This process is called oxidative phosphorylation.
• The enzyme involved in the synthesis of ATP is ATP synthase. This enzyme is located in the inner mitochondrial membrane.
• Following is a diagrammatical representation of mitochondria:

          ​     

​

• The enzyme ATP synthase gets activated when there is a proton gradient with a higher concentration of H⁺ ions on the F₀ side as compared to the F₁ side. This theory was proposed by Peter Mitchel and it is known as the chemiosmotic hypothesis.
• Thus according to the chemiosmotic coupling hypothesis of oxidative phosphorylation, adenosine triphosphate (ATP) is formed because of the proton gradient that is formed across the inner mitochondrial membrane.

So from the above-given explanation, the correct answer is option 1 (A proton gradient forms across the inner mitochondrial membrane).

Key Points

• Phosphorylation refers to a process of addition of a phosphate group to a compound by reacting with inorganic phosphate or transfer of phosphate group from another organic phosphate.
• Oxidative phosphorylation is a metabolic pathway by which ATP is formed as a result of phosphorylation reaction from ADP.
• It forms an important part of the cellular respiratory system and is vital for energy production.
• Cellular respiration starts with glycolysis in the cytoplasm where glucose molecules are broken down to form pyruvate, ATP and NADH.
• Pyruvate goes into the TCA cycle which takes place in the mitochondrial matrix, to produce NADH and FADH₂.
• After glycolysis and TCA cycle, there are 4 molecules of ATP, 10 molecules of NADH and 2 molecules of FADH₂ produced from 1 molecule of glucose.
• The NADH and FADH2 molecules transfer electrons to molecular oxygen and such redox reactions release energy to drive the phosphorylation of ADP.
• In order to harvest this energy in usable form, the release of energy should be gradual and thus, the electrons are transferred through a series of carriers located in the inner mitochondrial membrane.
• This is known as the Electron Transport Chain (ETC) and oxidative phosphorylation is linked to this.
• The ETC comprises of different protein complexes that act as electron carriers:
  • Complex I - is NADH dehydrogenase that transfers electrons from NADH to Coenzyme Q (Ubiquinone).
  • Complex II - is succinate dehydrogenase that transfers electrons from succinate (TCA cycle intermediate) to coenzyme Q via FADH₂.
  • Complex III - receives the electrons from coenzyme Q, passes it from cytochrome b to cytochrome c and ultimately to complex IV.
  • Complex IV - is cytochrome oxidase that carries electrons from cytochrome c to molecular oxygen, reducing it to H₂O.
  • Complex V - is ATP synthase that has the F₀ and F₁ components that are responsible for driving the phosphorylation reaction of ADP to form ATP.

Important Points

•  The electron transfers are coupled with proton transport from the matrix outwards through the complexes I, III and IV.
• This creates a proton gradient across the inner mitochondrial membrane.
• The proton gradient forms a pH gradient as well as electric potential, which forms an electrochemical gradient together and drives the protons back into the matrix from cytosol.
• The ATP synthase complex acts as a protein channel for the protons to move through as the membrane itself is impermeable to ions.
• As the protons move through the F₀ component, the F₁ component undergoes rotation that drives ATP synthesis.
• Oxidative phosphorylation yields 32-34 ATP molecules.