Before we understand the complex terms of this Biology respiration in plants class 11 chapter, let's begin with the basics. So, you already know that respiration in plants deals with how plants breathe. Now, let's understand it in detail.

 

What is respiration in plants? 

It is the method by which plants take in oxygen and release carbon dioxide into the environment.  The process needs glucose for its initiation. It is then converted into water and other by-products. It is a catabolic process that requires the oxygenation of the food that plants produce.

 

All these processes take place under photosynthesis. Since this process releases energy, it is used for various purposes like movement, reproduction, absorption and even breathing. That's why the whole process of cellular respiration has a crucial role to play in an organism's life. If these processes do not take place, no other processes can follow.

Like humans, plants do not have respiratory organs. That's why it can be quite difficult to understand how the whole process of breathing takes place in plants. But it is an important topic and will help you find respiration in plants class 11 NCERT solutions.

 

Plants only respire. The process of respiration is carried out by the presence of organs like lenticels and stomata.

 

They do not need any respiratory organs because: 

• • During photosynthesis, oxygen is released that is used by parts of the other plants like leaves. Diffusion takes place there. 

  • Plants carry out the process of gaseous exchange on their own.

  • The gaseous exchange is simple.

  • The diffusion of gases over large distances does not have an excellent record. 

 

During respiration, oxygen is utilised well by the plants and carbon dioxide and water are released along with a large amount of energy in the form of ATP.

 

This ATP is broken down whenever the plant requires energy. Therefore, it is called the energy currency of the plants. 

This term was proposed by Gustav Embden, Otto Meyerhof, and J. Parnas. It is also called the EMP Pathway. 

 

Glycolysis is the partial oxidation of glucose or hexose sugar. It is then converted into two molecules of pyruvic acid with the help of enzymes. It also releases ATP and NADPH2 as energy. All these processes take place in the cytoplasm. 

 

It is further carried out in different processes. Let's understand that glucose is obtained from sucrose or other such sugars. It is the work of the enzyme invertase that glucose is obtained from sucrose. 

 

Now, if we look further into glycolysis, it starts with the process of phosphorylation of glucose. This process takes place under the influence of an enzyme known as hexokinase. One ATP molecule is used here. The resulting product is Glucose-6-phosphate. 

 

Now, when the enzyme phosphohexose isomerase comes into play, it converts Glucose-6-phosphate into Fructose-6-phosphate. Further, the Fructose-6-phosphate is converted into Fructose 1-6 phosphate due to the action of the phosphofructokinase enzyme. In this, one ATP molecule is used. 

 

The net energy gain in glycolysis is 8 ATP. Let's understand how. During the phosphorylation of glucose, about two ATP molecules are used up. Further, two molecules of NADPH2 are formed during the oxidation of the glyceraldehyde 3-phosphate. As we know, each NADPH molecule is equivalent to 3 ATP. That's why the net gain is 8. 

 

The key product formed in glycolysis is pyruvic acid. The breakdown that follows of pyruvic acid is dependent on the cell's needs. Pyruvate can be transported to the mitochondria for further breakdown.

 

As you might already be familiar with, this process consists of the incomplete oxidation of glucose. It takes place in a condition where there is a lack of oxygen or the presence of no oxygen. These conditions are called anaerobic conditions. A series of reactions conduct the whole process. 

 

Pyruvic Acid that we've mentioned earlier gets converted to carbon dioxide and ethanol (alcohol). The reactions take place in the presence of enzymes known as alcohol dehydrogenase and acid decarboxylase. If we are talking or referring to bacteria, it converts pyruvic acid to lactic acid. 

 

Fermentation is not common to just plants. It can also take place in humans due to lack of oxygen or fatigue. These conditions are created during excessive exercises or workouts that involve the muscles. In this case, pyruvic acid is reduced to lactic acid. This takes place under the influence of the lactate dehydrogenase enzyme. 

 

If we refer to the fermentation in yeast, the pyruvic acid is converted to ethanol and carbon dioxide. A smaller amount of energy is released. Moreover, yeast can poison themselves if the alcohol concentration exceeds 13%. It is known as yeast poisoning. 

 

Both lactic acid and alcohol fermentation can be harmful. Fermentation is used in our daily life in numerous activities like baking, the formation of curd, vinegar, alcoholic beverages, and so on. 

 

Aerobic Respiration simply refers to the respiration that takes place in the presence of oxygen. It uses oxygen for all the chemical reactions that take place in the plants. Oxygen is essential for breaking glucose to generate energy that can be used by the plants later. It is the best and most effective source of energy for plants. All plants and animals that engage in aerobic respiration are known as aerobes.

 

The reactions in plants are: 

C6H12O6 +6O2 ⟶ 6CO2 + 6H2O + Energy

 

Aerobes can't survive without oxygen. It is their main source of energy from the food that they consume.

It is the opposite of aerobic respiration. Respiration that takes place in the absence of oxygen is known as anaerobic respiration. There is incomplete oxidation of glucose that takes place. The product formed is alcohol, carbon dioxide, and even acids like oxalic acid, citric acid, etc. 

 

Glucose ⟶ Alcohol + CO2 + (Energy)

 

It takes place in certain bacteria, yeast, and fungus. All these organisms can survive even without oxygen. They are called anaerobes. They gain energy through the process of anaerobic respiration. 

It is the net gain of ATP from all the reactions that take place. The following assumptions can calculate the gain of ATP: 

• • The NADH obtained from glycolysis is further transferred to mitochondria. Here, it goes through phosphorylation.

  • The other intermediates present do not synthesise other compounds.

  • Only glucose is used in respiration. 

  • The other intermediates or substrates don't enter this pathway at all.

 

As you can see, a total of 36 ATP are gained from these. 

As mentioned above, all the reactants are converted to glucose first for respiration. It is the most favoured substrate. 

 

We see that fats are reduced to glycerol and fatty acids. This further undergoes the breaking down of the compounds. Later, it is converted to Acetyl CoA, and then it enters the respiratory pathway. In this way, proteins break into amino acids. Further, it enters the Krebs cycle.

 

A reaction that involves breaking down compounds is known as catabolism, and the reaction that requires synthesis is anabolic. Hence, respiration is termed an amphibolic pathway.

It is the ratio of the carbon dioxide produced in respiration to the amount of oxygen consumed for respiration.

 

1. What are the core stages of aerobic respiration? Where does it take place? 

It involves the use of oxygen and the liberation of carbon dioxide. It takes place in the presence of oxygen. In plants, it takes place in lenticels and stomata.

 

2. What kind of assumption is made during the calculation of the net gain ATP? 

The NADH obtained from glycolysis is transferred to mitochondria, wherein it undergoes phosphorylation.

The other intermediates present do not produce different compounds.

Only glucose is used in respiration. 

The other intermediates or substrates don't enter this pathway at all.

 

3. What concepts can I learn from the NCERT solutions for class 11, chapter 14? 

They are plant respiration, aerobic and anaerobic respiration, glycolysis, fermentation, the respiratory balance sheet, amphibolic pathway, and respiratory quotient.

 

4. What are the aerobic respiration NCERT solutions?

It refers to the respiration that takes place in the presence of oxygen.

 

5. What is the respiratory balance sheet class 11?

It refers to the total gain of ATP molecules or energy during the respiratory process. 

 

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