CBSE Class 11 Biology Revision Notes Chapter 12

CBSE Class 11 Biology Revision Notes Chapter 12 – Mineral Nutrition

Chapter 12 of Class 11 Biology is focused on Mineral Nutrition for plants. All living things require minerals such as carbohydrates, proteins and fats, and water for their growth and development. This chapter focuses on inorganic plant nutrition and the essential nutrients that plants need to sustain and grow.

Extramarks offers Class 11 Biology Chapter 12 Revision Notes that summarise all the key concepts covered in this chapter in an easy-to-understand language. There may be topics in the textbook where students can get stuck. These notes help students get the conceptual knowledge of that topic and get their doubts cleared easily and quickly.

Access Class 11 Biology Chapter 12 – Mineral Nutrition Notes

Chapter 12 focuses on Plant nutrition. Some of the important concepts covered in the chapter are explained below.

Mineral Nutrition

There are certain nutrients that are required for all living creatures to survive, such as proteins, carbohydrates, water, lipids, and minerals. These are also important for plants for their development and growth.

Methods of Studying Mineral Needs of Plants

• There is a method called Hydroponics which involves growing plants in nutrient solutions instead of soil. It is used where there is commercial cultivation of vegetables. Also, for researching plant mineral deficiency disorder, this method of growing plants is utilised.
• Aeroponics is another method of spraying nutrients floating in the air over plants.

Essential Mineral Elements

Depending upon various plants, their need for minerals varies. There are criteria that determine whether an ingredient is necessary for a plant or not.

• A particular element must be necessary for the plant to complete its development and reproduction.
• The requirement of the element should be precise. There should not be any element that can substitute it.
• There should be a direct role of elements in plant metabolism.

Two kinds of mineral elements required by Plants are Macronutrients and Micronutrients.

Macronutrients

Macronutrients include Carbon, oxygen, hydrogen, phosphorus, sulphur, Potassium, Nitrogen, calcium, and Magnesium

CO2 and H2O are the most common hydrogen, Carbon, and oxygen sources. Plants receive others as mineral nourishment from the soil. Plants require these in large quantities.

Micronutrients

Iron, Copper, Manganese, Zinc, Boron, Molybdenum, Chlorine, and Nickel fall in this mineral element category. Plants require these in small amounts.

Essential Elements

1. Various essential elements such as hydrogen, carbon, oxygen, and Nitrogen are considered structural elements of the cells because they serve as components of numerous biomolecules like amino acids, lipids, etc., and are categorised into distinct groups as per their unique activities.
2. Essential elements like magnesium ion in chlorophyll and Phosphorus in ATP are significant components of chemical compounds associated with energy.
3. Essential elements operate as inhibitors and enzymes’ activators, influencing their function. Mg2+ activates both ribulose bisphosphate carboxylase oxygenase and phosphoenolpyruvate carboxylase. Both of these are required for carbon fixation to occur. Zn2+ activates alcohol dehydrogenase during nitrogen metabolism, while Mo is required for nitrogenase activity. 
4. A few key components control the osmolarity of a cell. The stomata open and close in response to potassium ions.

Role of Macronutrients and Micronutrients

The role of different Macronutrients and Micronutrients are-

Nitrogen

• A considerable amount of Nitrogen is required by the plants.
• Certain plants absorb it as nitrate ions (NO2), and some plants take it as ammonium ions (NO4)+.
• It is an essential vitamin component required for actively developing tissues like meristematic tissues.
• It has a direct role in photosynthesis.

Phosphorus

• Plants absorb Phosphate ions (PO4)3+
• It is found in large quantities in proteins, nucleotides, nucleic acids, and cell membranes.
• It enhances the growth and development of the plant roots.
• For the formation of seeds, this nutrient is required.
• It is also involved in the transport and storage of energy.

Potassium

• Potassium is rich in actively developing tissues, such as buds, meristematic tissues, root tips, and leaves.
• Osmotic potential is sustained by this element in plants responsible for stomatal opening and closing.
• Potassium increases photosynthetic rates.
• Protein synthesis also depends upon this element.

Calcium

• Plants absorb calcium ions (Ca2+) for ongoing cell division and development.
• Calcium plays an essential role in nitrogen metabolism.
• In the middle lamella, it exists in the form of calcium pectate.
• It is necessary for the development of the mitotic spindle.
• It is also vital for activating certain enzymes.

Magnesium

• It helps activate the enzymes that are involved in photosynthesis and respiration.
• Plants absorb Magnesium in the form of magnesium ions (Mg2+).
• It facilitates the production of DNA and RNA.
• It is an essential component of chlorophyll and helps maintain ribosome structure.

Sulphur

• It is an essential component of amino acids such as methionine.
• It is an element that helps in seed production in plants.
• For the creation of chlorophyll, it is quite essential.

Iron

• It is generally absorbed by the plants in the form of ferric ions (Fe3+) and is necessary for cell development and division.
• During a wide range of metabolic processes, it helps transport electrons.
• It is required to activate catalase enzymes which are further necessary for chlorophyll synthesis.

Manganese

• It is absorbed by the plants in the form of ions (Mn2+).
• It is essential for nitrogen metabolism.
• During non-cyclic photophosphorylation, it is required in the photolysis of water.

Zinc

• The body of the plants absorbs zinc ions (Zn2+).
• It is essential for the production of chlorophyll.
• It is responsible for activating a large number of enzymes, including carboxylases.
• It is necessary for carbohydrate synthesis.

Copper

• Plants absorb this in the form of cupric ions (Cu2+).
• It plays a role in redox reactions during the metabolic process.
• It performs the reproductive and photosynthesis functions in plants.
• This ion contributes to the flavour of fruits and vegetables.
• The amount of sugar in the plants is increased by this ion.

Boron

• It is absorbed by the plants in the form of BO33 or B4072-.
• It helps in calcium absorption.
• It helps in the development of pollen tubes.
• It assists in the transport of plant carbohydrates.
• It also helps in cell differentiation.

Molybdenum

• Plants absorb Molybdenum in the form of molybdate ion (MoO2)2-
• This ion, along with iron, forms the enzyme’s catalytic site. It is the main component of the Nitrogenase enzyme.
• It is an integral part of the nitrate reductase enzyme.

Chlorine

• Chlorine is absorbed by the plants in chloride ions (Cl1-) form.
• It helps in maintaining the osmotic potential of the cells.
• It plays a part in the photolysis of water, resulting in oxygen production.

Symptoms of Deficiency of Essential Elements

• One of the essential elements in plants is Nitrogen. The deficiency of Nitrogen causes yellowing of the leaves of the plants.
• The deficiency of Phosphorus causes burned and yellowish tips of the leaves.
• Interveinal Chlorosis and wilting of older leaves are caused due to the deficiency of Potassium.
• Calcium deficiency causes Blossom end rot.
• With the deficiency of Magnesium, older leaves turn yellow. This condition is called Chlorosis, and it happens when chlorophyll is degraded.
• With the deficiency of Sulphur, younger leaves become more yellow than the older leaves.
• Iron deficiency causes Chlorosis of leaves. Plants suffer from Dieback disease due to iron deficiency.
• The deficiency of Manganese causes yellowing between the leaves’ veins and dead patches on the components of the plants.
• Rosettes get developed in plants due to the deficiency of zinc.
• Plant cell walls and stems get weaker due to the deficiency of Copper.
• The deficiency of Boron affects the reproductive system of plants.
• Growth is retarded due to the deficiency of Molybdenum.
• Chlorosis, wilting, necrosis in the tissues and a highly branching root system are caused due to the deficiency of chlorine.

Metabolism of Nitrogen

Three nitrogen atoms linked with a triple covalent (N ≡ N) bond form ammonia. The process of converting Nitrogen into ammonia is known as nitrogen fixation.

There are two ways to convert Nitrogen into ammonia:

• When lightning strikes, the physical nitrogen fixing happens. The N2 and O2 present in the atmosphere reacts in the presence of lightning to create NO (Nitric Oxide). NO is further oxidised to form nitrogen peroxide (NO2).
• When dead plants and animals decompose, ammonia is produced. This process is known as ammonification. When ammonia is converted into nitrite, and ultimately to nitrate, this process is known as Nitrification. Nitrite is formed in the presence of Nitrosomonas bacteria, and nitrate is formed in the presence of Nitrobacter bacteria.

Biological nitrogen fixation only occurs if there is a presence of nitrogen-fixing microorganisms such as Rhizobium. Diazotrophs are prokaryotes that are responsible for biologically fixing Nitrogen. It is a symbiotic bacteria that live in the roots of leguminous plants.

Nitrogenase is an enzyme that plays a role in biological nitrogen fixation. Both symbiotic and free-living nitrogen-fixing bacteria exist. Rhodospirillum, Azotobacter, Nostoc, and Anabaena are some of the free-living nitrogen-fixing aerobic bacteria.

Leguminous plants like beans, peas, alfalfa, clover, etc., have a symbiotic relationship with Rhizobium. The development of distinctive nodules accompanies Nitrogen-fixing. The first step in the development of the nodules is the contact of Rhizobium with the roots of the plants. The bacteria are attracted to the roots of the plants due to the release of certain compounds. A root hair curling compound is produced by Rhizobium that helps in bacteria’s invasion of the roots. The nitrogenase enzyme responsible for catalysing nitrogen fixation is oxygen sensitive. The enzyme leghemoglobin scavenges oxygen during nitrogen fixation.

Reductive Amination and Transamination

Transamination: It transfers an amino group from one amino acid to a keto acid. Transaminases are enzymes that catalyse this process of Transamination. As a result, Asparagine amino acids are formed. With this process, the poisonous ammonia is transformed into essential amino acids that can help the growth and development of the plant.

Notes of Chapter 12 Biology Class 11 Free Download

Revision notes by Extramarks will help students prepare more effectively. They won’t have to prepare their own notes and can refer to the notes prepared by subject matter experts for last-minute preparations and revisions. Since the notes are authored in easy-to-understand language, students can refer to these notes if they are unable to understand any concept from the textbook. These notes can be accessed any time from the Extramarks’ website.

Contents of Biology Class 11 Chapter 12 Notes

In this chapter, students will learn that the minerals that plants usually require are absorbed from the soil. However, some of the mineral requirements of the plants need to be fulfilled by Hydroponics. Minerals are categorised into two major groups depending on the number of minerals required for the plants for healthy living.

• Macronutrients: These are the elements required by living beings in a large quantity and are thus known as macronutrients. Some instances of macronutrients are oxygen, hydrogen, and Nitrogen.
• Micronutrients: These are the elements required in smaller quantities known as micronutrients. Examples of micronutrients include zinc, iron, and Copper.

Notes of Class 11 Biology Chapter 12 consists of functions of both types of these minerals. This chapter also includes the study of diseases that plants suffer from due to the minerals deficiency falling into these two categories. In this chapter, the metabolism of Nitrogen and its uses are also explained. Students can have a complete idea of the content of this chapter by using these revision notes. 

Subtopics in Class 11th Biology Chapter 12 Notes

Let’s look at the sub-topics discussed in this chapter’s notes.

• What is mineral nutrition in plants?
• What are macro and micronutrients?
• Grouping essential elements according to their functions
• The function of essential elements, such as:

Nitrogen: Nitrogen plays a vital role in the plant’s growth and photosynthesis.

Phosphorus is an essential element required for growth, seed formation, and energy transfer.

Potassium: It is necessary to maintain osmolarity.

Calcium: It is required for signal transduction.

Magnesium: It is needed for photosynthesis.

Sulphur: It is required for protein structuring and is also an essential component of vitamins.

Iron: It helps in signal transduction and enzymatic reactions.

Manganese: It helps in photophosphorylation.

Zinc: It is required for chlorophyll formation.

Copper: It is required for metabolic reactions.

Molybdenum: It acts as a catalyst for specific reactions.

Boron: It is an essential mineral for reproduction.

Chlorine: It helps maintain the potential of the cell.

• Symptoms of deficiency of mineral nutrients in plants.
• Metabolism of Nitrogen in plants

Tips to Study From Ch 12 Biology Class 11 Notes

Here are some valuable tips for students to ensure they get the best results with these revision notes.

• Many questions in the exams are directly asked from the textbook. So, read the NCERT textbook thoroughly and with attentiveness.
• You can figure out the section that you find difficult to understand from the textbook. Then find that section in the Chapter 12 Biology Class 11 notes and understand the concept. These notes will help you to clarify your doubts as they are presented in a comprehendible manner. 
• Practice the questions provided at the end of the chapter. Refer to the model answers provided with the notes. This way, you will be able to identify your limitations in answering a particular question. You can work out those limitations.
• Before the exam, go through the notes to recall essential points.