NCERT Solutions for Class 11 Biology Chapter 12 Respiration in Plants

NCERT Solutions for class 11 Biology Chapter 12 Respiration in Plants: The chapter on Respiration in plants is important for students approaching the board exams. This article introduces NCERT solutions designed to help students explain the concepts of further learning and how to write to get good grades on exams. The solutions are presented in very simple language for ease of understanding.

NCERT CBSE Chapter 12 Respiration in Plants of Class 11 Biology explains how living organisms, including plants and microbes, breathe. It further explains that all living organisms including plants need energy for carrying out daily life activities, be it absorption, transport, movement, reproduction or even breathing. Revise the basic concepts of Respiration in Plants for quick revision and class notes.

Q1: Differentiate Between

• (a) Respiration and Combustion
• (b) Glycolysis and Krebs’ cycle
• (c) Aerobic respiration and Fermentation

Answer:

(a) Difference Between Respiration and Combustion

Respiration	Combustion
It occurs inside living cells	It is a non-cellular process
Respiration is the biochemical process	Combustion is a physiochemical process
Most of the energy is trapped in ATP molecules	ATP is not formed

 (b) Difference Between Glycolysis and Krebs’ Cycle

Glycolysis	Kreb’s Cycle
It is an anaerobic process	It is an aerobic process
A molecule of glucose is converted into two molecules of pyruvic acid.	It involves the oxidation of pyruvic acid into water and carbon dioxide.
It takes place in the cytoplasm	It takes place in the mitochondria.

(c) Difference Between Aerobic respiration and Fermentation

Aerobic Respiration	Fermentation
It uses oxygen for breaking the respiratory material into simpler substances	Oxygen is not used in the breakdown of respiratory substrate
Respiratory material is completely oxidized	Respiratory material is incompletely broken
End products are inorganic	At least one of the products is organic

Q2: What are Respiratory Substrates? Name the Most Common Respiratory Substrate.

Answer:

The breaking of the C-C bonds of complex compounds through oxidation within the cells, leading to the release of a considerable amount of energy is called respiration. The compounds that are oxidized during this process are known as respiratory substrates. Carbohydrates are the most common respiratory substrate.

Q3: Give the Schematic Representation of Glycolysis.

Answer:

Glycolysis is the process by which one molecule of glucose is converted into two molecules of pyruvate, two hydrogen ions, and two molecules of water. The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J. Parnas, and is often referred to as the EMP pathway.

Q4: What are the Main Steps in Aerobic Respiration? Where does it take place?

Answer:

The main steps in aerobic respiration are:

• a) Glycolysis: Takes place in Cytoplasm.
• b) Kreb’s Cycle: Takes place in the Matrix of Mitochondria.
• c) Electron Transport System: Inner mitochondrial membrane.
• d) Oxidative Phosphorylation: Takes place in F0 –F1 particles in the inner mitochondrial membrane.

Q5: Give the Schematic Representation of an Overall view of Krebs’ Cycle.

Answer:

The Krebs cycle or TCA cycle (tricarboxylic acid cycle) or Citric acid cycle is a series of enzyme-catalyzed reactions occurring in the mitochondrial matrix, where acetyl-CoA is oxidized to form carbon dioxide and coenzymes are reduced, which generate ATP in the electron transport chain.

 Q6. Explain ETS.

Answer:

Electron Transport System refers to the mechanism of cellular respiration that occurs in the inner mitochondrial membrane. It is the third and last stage of cellular respiration.

ETS involves electron transfer through a series of protein complexes from higher (NADH+) to lower energy state (O2) by releasing protons into the cytosol. The movement of proton or H+ from a matrix to cytosol generates a proton motive force and creates an electrochemical gradient. Then, the proton molecules tend to diffuse down the electrochemical gradient again into the mitochondrial matrix and release ATP via ATP synthase. An oxygen atom is the last carrier, which accepts the electron and combines with the free hydrogen ions in the mitochondrial matrix to give water. Thus, the oxygen carrier maintains the membrane potential by removing the de-energized electrons from the inner mitochondrial membrane. 

Q7. Distinguish Between the Following:

• (a) Aerobic respiration and Anaerobic respiration
• (b) Glycolysis and Fermentation
• (c) Glycolysis and Citric acid Cycle

Answer:

(a) Difference Between Aerobic respiration and Anaerobic respiration

Aerobic Respiration	Anaerobic Respiration
It takes place in the presence of oxygen.	It takes place in the absence of oxygen.
Carbon dioxide and water are the end products.	Alcohol is the end product.
Aerobic respiration releases more energy	It releases less energy than aerobic respiration.

(b) Difference Between Glycolysis and Fermentation

Glycolysis	Fermentation
Breakdown of glucose into two molecules of pyruvic acid	Breakdown of glucose into CO2 and ethyl alcohol or lactic acid
Takes place in all organisms	Occurs in some microorganisms and fungi
Results in the production of 8 ATPs	Results in the production of 2 ATPs

(c) Difference Between Glycolysis and Citric acid Cycle

Glycolysis	Citric Acid Cycle
Occurs inside the cytoplasm	Occurs inside the mitochondria
No carbon dioxide evolved	Carbon dioxide evolved
Oxygen is not required for glycolysis	Oxygen is required for Citric Acid Cycle

Q8: What are the Assumptions made during the Calculation of the Net Gain of ATP?

Answer:

These calculations can be made only on certain assumptions:

• There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle, and ETS pathway following one after another.
• The NADH synthesized in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation.
• None of the intermediates in the pathway are utilized to synthesize any other compound.
• Only glucose is being respired – no other alternative substrates are entering the pathway at any of the intermediary stages.

Q9: Discuss “The Respiratory Pathway is an Amphibolic Pathway.”

Answer:

The respiratory pathway is called the amphibolic pathway because it involves both catabolism and anabolism. An amphibolic pathway is one that can be utilized to break down as well as makeup processes. When energy is required, proteins or fatty acids are broken down to form acetyl-CoA and further processes of respiration occur. This is catabolism. When the body requires fatty acids or proteins, the respiratory pathway stops and the same acetyl-CoA is utilized and fatty acids are manufactured. This process of synthesis is termed anabolism. Because the respiratory pathway is involved in both anabolism and catabolism, hence it is considered as an amphibolic pathway.

Q10: Define RQ. What is its Value for Fats?

Answer:

During aerobic respiration, O₂ is consumed and CO₂ is released. The ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio. When fats are used in respiration, the RQ is less than 1.

Q11: What is Oxidative Phosphorylation?

Answer:

Oxidative phosphorylation is a cellular process that harnesses the reduction of oxygen to generate high-energy phosphate bonds in the form of adenosine triphosphate (ATP). It is a series of oxidation-reduction reactions that involve the transfer of electrons from NADH and FADH2 to oxygen across several proteins, metal, and lipid complexes in the mitochondria.

Q12: What is the Significance of the Step-Wise Release of Energy in Respiration?

Answer:

The stepwise release of energy makes the system more efficient in extracting and storing energy.