Important Questions Class 11 Biology Chapter 14

Class 11 Biology Chapter 14 Important Questions – Respiration in plants

From plant physiology to its structure, different Biology sections explain the various components involved in the making of the plant body, its functioning, preparation of food, transpiration mechanisms and its relation with the environment. Thus this understanding would help us nurture the plants and facilitate their optimum growth. 

Since primary school, we have encountered various topics that emphasise plant growth and functioning. A brief understanding of plant processes and significance will help us easily comprehend the various sectors of plant life covered in this chapter. 

Chapter 14 of Class 11 Biology talks about the process of plant respiration. In the natural environment, plants produce their food to survive. The sugars and oxygen produced during photosynthesis supply energy for plant growth. The end products of photosynthesis are glucose and oxygen, which are used as starting products for beginning the process of cellular respiration. 

This chapter is essential from the perspective of various competitive examinations like NEET, MH- CET, and board examinations. Students should solve exercises and exemplar questions from the NCERT to prepare for their examinations. Extramarks has experienced faculty working conscientiously and diligently to prepare authentic, concise answers which students can trust and enjoy the process of learning while preparing for their exams. The systematic and well-laid-out balanced study plan boosts their performance naturally and effortlessly. 

Biology is a theoretical subject. Learning and going through various core concepts can become a time-consuming process. At Extramarks, we ensure that the students’ minutest doubts are resolved and they develop an interest in learning and mastering the topic with ease to excel in their

academic performance. The Biology experts at  Extramarks have curated Important Questions Class 11 Biology Chapter 14 using NCERT Textbook, NCERT Exemplar, various reference books, past examination papers, and other sources. Our Biology faculty experts have compiled a complete list of important questionnaires and step-by-step solutions to facilitate the students with the learning process in every way whether preparing for exams or competitive exams. 

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Access Important Questions of Respiration in Plants Class 11 for the Academic Year 2022-23.

Class 11 Biology Chapter-wise important questions are available for free to students, and these questions are perfect for self-study.

Check out CBSE Class 11 Biology Important Questions for other chapters as well:

CBSE Class 11 Biology Important Questions

Sr No. Chapters Chapters Name
1 Chapter 1 The Living World
2 Chapter 2 Biological Classification
3 Chapter 3 Plant Kingdom
4 Chapter 4 Animal Kingdom
5 Chapter 5 Morphology of Flowering Plants
6 Chapter 6 Anatomy of Flowering Plants
7 Chapter 7 Structural Organisation in Animals
8 Chapter 8 Cell the Unit of Life
9 Chapter 9 Biomolecules
10 Chapter 10 Cell Cycle and Cell Division
11 Chapter 11 Transport in Plants
12 Chapter 12 Mineral Nutrition
13 Chapter 13 Photosynthesis in Higher Plants
14 Chapter 14 Respiration in Plants
15 Chapter 15 Plant Growth and Development
16 Chapter 16 Digestion and Absorption
17 Chapter 17 Breathing and Exchange of Gases
18 Chapter 18 Body Fluids and Circulation
19 Chapter 19 Excretory Products and their Elimination
20 Chapter 20 Locomotion and Movement
21 Chapter 21 Neural Control and Coordination
22 Chapter 22 Chemical Coordination and Integration

Important Questions Class 11 Biology Chapter 14 With Solutions

Class 11 Biology Chapter 14 important questions have been curated for students after thorough analysis through multiple sources. The chapter covers cellular respiration, production of ATP, respiratory quotient, glycolysis, aerobic and anaerobic respiration, the process of fermentation, tricarboxylic acid cycle (Kreb’s cycle), photophosphorylation, terminal oxidation, electron transport chain, amphibolic pathway etc. The solutions for Important Questions Class 11 Biology Chapter 14 explain all these essential concepts in detail. 

The set of Important Questions Class 11 Biology Chapter 14 will cover the chapter’s major topics and help students revise their concepts easily. After going through these question-answer sets, students will be able to understand their strengths and weaknesses among the various topics covered in the chapter. This will help develop a strong foundation and revisit complex concepts to strengthen their learning.

Given below is a list of  questionnaires from the Important Questions Class 11 biology Chapter 14 with their solutions:


Question 1. Anaerobic respiration is observed in living entities such as humans and angiosperms in aerobic conditions. Why?

Answer 1: The process by which ATP is obtained by breaking down glucose without oxygen is called anaerobic respiration. During this process, electron acceptors are used in place of molecular oxygen to produce energy. Under normal conditions in human beings, aerobic respiration takes place. However, our muscles require more energy than usual under intense conditions like heavy exercise and strenuous workouts. The energy is then derived in the form of ATP. Due to the high consummation of energy, there is a lack of oxygen in the muscle cells. To produce more energy, muscle cells perform aerobic respiration. They produce lactic acid to meet their energy needs. In poor conditions of oxygen, yeast cells undergo aerobic respiration. The end products formed after this reaction are ethyl alcohol and carbon dioxide.

Question 2. Explain Glycolysis. State where it occurs and its end products. Both aerobic and anaerobic respiration determine the fate of these products.

Answer 2: The process in which glucose (A six-carbon compound) splits into two molecules of pyruvic acid (A three-carbon compound) is called an EMP pathway of glycolysis. The process of glycolysis takes place in the cytoplasm of the cell. Glucose is broken down anaerobically for pyruvic acid. Pyruvic acid is obtained from the sucrose present in plants which is a resulting product of photosynthesis. Sucrose gets converted into fructose and glucose by enzyme invertase. After which, these products enter the glycolytic pathway. An entire sequence of 10 reactions regulated by different enzymes occurs during glycolysis to yield pyruvate from glucose. Pyruvic is the chief product of glycolysis. The cellular need decides pyruvate’s metabolic fate. 

There are three modes in which cells manage pyruvic acid produced during glycolysis. They are lactic acid, fermentation, aerobic respiration, and alcoholic fermentation. In anaerobic conditions in unicellular eukaryotes and prokaryotes, fermentation occurs. The pyruvic acid produced during glycolysis enters the Krebs cycle. The Krebs cycle is observed in entities performing aerobic respiration. Complete oxidation of glucose gives end products like carbon dioxide and water, which require an oxygen supply. When aerobic respiration occurs, the molecule enters the Krebs cycle and the electron transport chain. There are 38 ATP molecules formed from aerobic respiration. 

During anaerobic respiration, the molecule gets broken down to form lactic acid or alcohol. There are 2 ATP molecules produced during this process. Learn more about glycolysis from Chapter 14 class 11 biology important questions, available on the Extramarks website.

Question 3. Discuss “The respiratory pathway is an amphibolic pathway.”

Answer 3: Respiration is usually assumed to be a catabolic pathway as various substrates are broken down to derive energy. Organic substances like fats, carbohydrates, proteins etc., release energy when broken down in the respiratory pathway. Carbohydrates are broken down to glucose before they enter the respiratory pathways. Fats are converted into fatty acids and glycerol, while fatty acids get converted into acetyl CoA before entering the process of respiration. In the same way, proteins are converted into amino acids. While the synthesis of fatty acids occurs, acetyl-CoA is withdrawn from the respiratory pathway. The process that serves as a catabolic pathway for the respiratory substrates also serves as an anabolic pathway for producing different metabolic products and secondary metabolites. Thus, the respiratory pathway serves as catabolic and anabolic pathways. Therefore, respiration can be called the amphibolic pathway, where catabolism and anabolism occur.

Question 4. What is oxidative phosphorylation?

Answer 4: Oxidative phosphorylation is a metabolic pathway. It generates ATP through phosphorylation, i.e. addition of phosphate to an organic compound of ADP by the electron transport system. The phosphorylation process occurs in the cell’s inner mitochondrial membrane. ATP synthase occurs when hydrogen protons pass through the mitochondrial membrane. The energy required during phosphorylation is derived from the oxidation-reduction phenomena in respiration. The ATP is formed after the transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers. Hence, the process is called oxidative phosphorylation.

Question 5. Oxygen is critical for aerobic respiration. Explain its role concerning ETS.

Answer 5: NADH2 and FADh2 are energy carriers in the electron transport system. They are utilised for the production of ATP. These electrons get transferred through a series of events and finally convert into oxygen molecules. The oxygen molecule works as the final hydrogen acceptor to form water molecules. Although in the final stage, oxygen becomes essential to perform the process of aerobic respiration. Oxidative phosphorylation involves a sequence of events through which electrons are transferred through an electron gradient. It is similar to the flow of water through a tap. Until the tap does not open , it prohibits the flow of even a single drop of water. Hence, subsequent drops of water cannot flow down. The oxygen acts as a hydrogen acceptor like a receptacle, collecting the first electron so the subsequent flow of electrons through ETS can be maintained. Hence, oxygen is required to create a gradient through which electrons can be transferred passively.

Question 6. The energy yield in terms of ATP is higher in aerobic respiration than during anaerobic respiration. Explain?

Answer 6: During aerobic respiration, there is complete oxidation of a glucose molecule. However, in anaerobic respiration, incomplete oxidation of glucose molecules occurs. As a result, energy production is more during aerobic respiration than in anaerobic respiration. In both processes, ATP is formed. However, the number of ATP molecules formed in aerobic respiration is more than in anaerobic respiration. 

In aerobic respiration, a total of 36 molecules of ATP are produced per one molecule of glucose; in anaerobic respiration, one molecule of glucose yields two molecules of ATP. Hence energy yield is higher in aerobic respiration.

Students are advised to visit the Extramarks website and access Biology Class 11 Chapter 14 important questions and other study resources for more information on energy yields in aerobic and anaerobic respiration.

Question 7. Who is the competitive inhibitor of the enzyme succinate dehydrogenase?

Answer 7: A substrate analogue that combines reversibly to the free enzyme at the active site without getting transformed is called a competitive inhibitor. Competitive inhibition is a form of enzyme inhibition in which the inhibitor binds to the active site on the enzyme. As the inhibitor binds on the active site, it inhibits the binding of the substrate and vice versa. Malonate or oxaloacetate resembles the structure of succinate dehydrogenase. Hence, they act as an inhibitor and bind to the active site of succinate dehydrogenase. Such competitive inhibitors are usually used for the control of different bacterial pathogens. Hence, malonate is the competitive inhibitor of the enzyme succinate dehydrogenase.

Question 8. Explain fermentation.

Answer: Cellular respiration, which takes place without oxygen, is called aerobic respiration. Fermentation is an anaerobic pathway which is a common pathway that takes place in the majority of prokaryotes and unicellular eukaryotes. In this process, glucose gets partially oxidised to form acids and alcohol. Plants carry out incomplete oxidation of glucose during the process of fermentation. Fermentation takes place under anaerobic conditions through a sequence of reactions. 

In organisms like yeast, glucose forms pyruvic acid through partial oxidation. Pyruvic acid gets converted into ethanol and carbon dioxide (CO2) in the further steps. This anaerobic condition is termed alcoholic or ethanol fermentation. The entire reaction is catalysed by two enzymes called pyruvic acid decarboxylase and alcohol dehydrogenase. 

In a few animal muscle cells and bacteria, the pyruvic acid is reduced to lactic acid by lactate dehydrogenase under anaerobic conditions. NADH2 is the reducing agent which oxidises to NAD+ while the following steps are carried out. This process is called lactic acid fermentation. The end products like lactic acid of these anaerobic pathways are harmful. They are termed to be hazardous processes. For example, if the concentration of alcohol produced by yeast cells increases above 13%, The yeast cells could kill themselves: alcohol and lactic acid fermentation release significantly less energy. We use the process of fermentation in  food, beverage and pharmaceutical industries. A wide variety of products such as curd, vinegar, bread and alcoholic drinks are formed after the process of fermentation.

Key Topics Covered in Chapter 14 Biology Class 11 Important Questions

Following are the  key points that are covered in Important Questions Class 11 Biology Chapter 14 are:

  1. Introduction to respiration:

Respiration is an energy-releasing process. It is an enzymatically controlled catabolic process. Respiration involves a step-wise oxidative breakdown of various food substances inside the living cells. Living organisms need energy for performing different activities like absorption, movement, reproduction and even breathing. The energy required to carry out these functions is obtained from the oxidation of food during respiration.

  1. Cellular respiration:

Cellular respiration is the mechanism by which food materials are broken down inside the cells to release energy. Cellular respiration is carried out for the synthesis of ATP. In cell organelles, like cytoplasm and mitochondria, various functions occur. The breakdown of complex molecules into simpler compounds yields energy in these organelles. The broken compounds that oxidise after C-C bonds are called respiratory substrates.

  1. Respiratory Quotient:

When respiration occurs, oxygen is utilised, and carbon dioxide and water are released along with energy molecules in the form of ATP. The ratio of the volume of carbon dioxide produced to the volume of oxygen consumed during respiration over some time is known  as respiratory quotient. The symbol for the respiratory quotient is RQ. The respiratory quotient (RQ) is equal to one for carbohydrates and less than one for protein and peptones.

  1. Glycolysis:

Gustav Embden, Otto Meyerhof, and J. Parnas gave the scheme for glycolysis. It is also known as the EMP pathway. Glycolysis is the partial oxidation of glucose or similar hexose sugar to break down into two molecules of pyruvic acid through a series of reactions releasing ATP and NADH2. This process is enzyme-mediated and takes place in the cytoplasm.

  1. Tricarboxylic acid cycle/Krebs cycle:

The krebs cycle was discovered by Hans Krebs in 1940. It is also called the TCA cycle because the initial product of the reaction is citric acid. Acetyl CoA combines with OAA (Oxaloacetic acid) and water. They yield citric acid. This is an enzyme-mediated process in the presence of enzyme citrate synthase to release CoA. Citrate is then isomerised to isocitrate. 

  1. Electron Transport Chain:

ETC or mitochondrial respiratory chain is the metabolic pathway through which the electron passes from one carrier to another. ETC takes place inside the inner mitochondrial membrane of the cell. At the same time, the transfer of electrons occurs from one carrier to another via the ETC. ATP is produced from ADP. Along with ATP, inorganic phosphate is also formed. The number of ATP molecules synthesised is dependent on the electron donor. Oxidation of one molecule of NADH results in 3 molecules of ATP, while oxidation of one molecule of FADH yields two molecules of ATP.

Benefits of Solving Important Questions Class 11 Biology Chapter 14

Biology lays greater emphasis on conceptual learning and understanding. By reading and solving exercises based on the chapter, students can prepare well for their examinations. We recommend students to register themselves at Extramarks and access the study material designed by the subject matter experts. Before preparing for examinations, teachers always advise us to revise all chapters and build our conceptual knowledge. Using our wide range of study materials, students can revise different chapters multiple times and get good grades. Following are the benefits of  Solving Important Questions Class 11 Biology Chapter 14:

  • Students can entirely rely on the Important Questions Class 11 Biology Chapter 14 as they are prepared following the NCERT textbooks and adhere to the latest guidelines provided by  CBSE
  • These are a set of questions given that are more likely to be asked in examinations. This gives students a general idea of the questions they may face during exams and are not caught off guard. Hence, keep them prepared to solve any tricky questions through their study material.
  • The Biology faculty experts have prepared the questions at Extramarks, that help students conveniently recall the crucial points in the exam and use these solutions for last-minute revisions. These resources are reliable and accurate. In fact, these resources are the best study material for getting a 100% score and creating your first milestone in high school. 
  • Our team has given step-by-step solutions to help students easily revise essential concepts and theories. Students can access multiple resources from Extramarks as per their preparation level from the Extramarks official website

Q.1 Which of the following substrates will have maximum respiratory quotient?



The respiratory quotient of barley (carbohydrate) is 1 and that of soybean (protein) is 0.9. While the respiratory quotient of almonds and chia seeds (fat) is less than 1.

Q.2 One molecule of glucose requires 2 ATP to get phosphorylated to form fructose 1-6 Biphosphate in glycolysis. The ATP which are used in the same process if the substrate is fructose is




Whether it is glucose or fructose, reactions are same.

Q.3 In Krebs cycle, the number of reduced coenzymes formed is



One turn of Krebs cycle produces four reduced coenzymes (2NADH2, 1NADH2 and 1FADH2) and 2CO2. In all, there are two turns of Krebs cycle for the oxidation of 1 molecule of glucose.

Q.4 One turn of Krebs cycle for the oxidation of 1 mol of sucrose produces



Whether it is glucose/sucrose, one turn of Krebs cycle produces 12 ATP. In sucrose, there will be in all four turns of Krebs cycle instead of two, as in case of glucose, and therefore, total ATP production will be two times more than glucose, that is 76 ATP.

Q.5 The step of glycolysis where NADH+H+ is formed:



The step of glycolysis where NADH+H+ formed is 3-PGA to 3-biphosphoglycerate.


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