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NCERT Solutions for Class 11 Biology Chapter 9 Biomolecules help students understand the complex biological concepts. This chapter provides essential information about the chemical compounds that form the basis of life. It includes compounds such as carbohydrates, proteins, lipids, and nucleic acids. With the help of these solutions, students can strengthen their understanding, identify and work on weak areas, and build a solid foundation in the subject of biology.
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If students find any difficulty in understanding the concept of biomolecules, they are on the right platform. The answers are written in a simple and easy-to-read manner to help students improve their conceptual clarity and perform well in exams. Biomolecules play an important role in various biological processes necessary for growth, development, and metabolism. By doing regular practice with the NCERT Solutions, students can not only increase their knowledge in the subject of Biology but also gain confidence to perform well in the exam.
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The PDF for the chapter Biomolecules can be downloaded from the link given below. It can be used offline anytime for quick revision or homework help. This makes it easier to understand complex topics like carbohydrates, proteins, and enzymes. These NCERT Solutions for Class 11 are also useful for regular study and exam preparation.
The complete solved exercise is given below. Each question is answered step by step to improve understanding and clarity. Studying through the Class 11 Biology Chapter 9 Biomolecules question and answer allows students to understand the structure and function of molecules clearly.
Q1. What are macromolecules? Give examples.
Answer:
The complex high molecular weight molecules separated in acid-insoluble fractions in the assistance of trichloroacetic acid are referred to as macromolecules. They are polymers of a molecular weight of 10,000 daltons and above. Proteins, carbohydrates, nucleic acids etc., are macromolecules. There are lipids in the acid-insoluble fraction too, but they are not of high molecular weight.
Q2. Illustrate a glycosidic, peptide and a phospho-diester bond.
Answer:
Glycosidic bond- This bond is formed between the 1st carbon atom of one monosaccharide and 4 carbon atoms of a neighbouring monosaccharide unit. During the formation of this bond, a water molecule is released. A representation of a glycosidic bond is as follows
Peptide bond- This is a covalent bond formed between the carboxyl group of one amino acid and the amino group of neighbouring amino acids. A water molecule is released in the formation of a peptide bond. A representation of a peptide bond is as follows
Phosphodiester bond- It refers to the phosphate-hydroxyl linkage between two nucleotides. In this bond, the phosphate attached to the hydroxyl group at the 5' carbon of the pentose sugar is in turn bonded to the hydroxyl group of the 3' carbon of the pentose sugar of the next nucleotide.
Q3. What is meant by the tertiary structure of proteins?
Answer:
The three-dimensional configuration of a protein that arises from repeated coiling and folding of helical and pleated polypeptide chains is termed its tertiary structure. Through repeated folding and coiling, polar side chains remain exposed whereas non-polar amino acids are kept inside. The tertiary structure is bonded through weak bonds. The activity of a protein exists in tertiary structures.
Answer:
The structures of 10 small molecular weight biomolecules are as follows
These biomolecules are manufactured in biotechnology industries.
Answer:
Proteins with therapeutic uses are insulin, oxytocin, ADH, thrombin, fibrinogen, renin, immunoglobulin, diastase, streptokinase etc.
Other applications of proteins are
1. As cosmetics- Protein such as casein is used in beauty creams, shampoos etc.
2. Sweeteners- Thaumatin and monellin are sweet proteins.
3. Dietary supplements- Proteins can be used as dietary supplements.
Q6. Explain the composition of triglyceride.
Answer:
A triglyceride is a chemical formed by the esterification of three molecules of fatty acids with one molecule of trihydric alcohol called glycerol. All three fatty acids of triglyceride can be similar as in tripalmitin or dissimilar as in palmito-oleoistearin, dipalmitostearin, etc.
Answer:
Milk has a protein known as casein. When we mix a little curd into milk, the protein casein is coagulated by the action of lactic acid bacteria and thus milk is transformed into curd. Coagulation breaks the structure of the protein casein.
Answer:
Yes, we can try constructing models of biomolecules with the help of commercially purchased atomic models like ball and stick models. The stick is, in the model, taken to be a bond and balls of varying colours are taken to be atoms.
Answer:
When we titrate an amino acid against a weak base, it dissociates into its functional groups i.e. -COOH (carboxylic group) and -NH (amino group)
Q10. Draw the structure of the amino acid, alanine.
Answer:
The structure of the amino acid alanine is represented below:
Answer:
One of the qualitative tests for proteins is the xanthoproteic test. When a qualitative test for protein in urine is done using the aid of the xanthoproteic test, if a yellow precipitate is formed, then it is guaranteed that there is protein in it. The qualitative test for fats is the emulsification test.
During the emulsification test, the experimental material is first treated with ethanol and then dissolved in water. The development of emulsion proves the existence of fats. The qualitative analysis for oils is the paper test. The material to be tested is placed on paper. The presence of oil is established when oil marks remain.
Answer:
Paper consists of wood pulp, which is predominantly composed of cellulose. Cellulose is a polymer of glucose molecules. Approximately 85 billion tonnes of cellulose are generated every year in the biosphere. Paper production requires 0.5 billion tonnes of wood. The rise in the usage of wood has caused immense loss of vegetation.
Q13. Describe the important properties of enzymes.
Answer:
Enzymes are proteinaceous substances which are capable of catalysing chemical reactions of biological origin without themselves undergoing any change. They are commonly called biocatalysts. The properties of enzymes are as follows:
1. Enzymes are proteins by nature
2. Optimum temperature- An enzyme is active within a narrow range of temperature. The temperature at which an enzyme is most active is called the optimum temperature. The enzyme activity decreased above and below this temperature.
3. Optimum pH- Every enzyme has an optimum pH at which it is maximum active. Most of the intracellular enzymes work at neutral pH.
4. Enzymes are substrate specific, i.e. one enzyme catalyses only a particular substrate. Every enzyme has specific sites called active sites for the binding of substrate.
5. Only a small quantity of the enzyme is capable of forming the desired product
6. Enzyme activity is sensitive to certain chemicals called inhibitors or modulators.
Check the NCERT Books and NCERT Syllabus here:
To answer Biomolecules questions, just follow the simple steps:
NCERT Solutions for Class 11: Subject-wise
This chapter explains the structure, types, and functions of essential biomolecules like carbohydrates, proteins, lipids, and nucleic acids found in living organisms.
Question: What type of bond joins monosaccharides in polysaccharides?
a. Peptide bond
b. Glycosidic bond
c. Phosphodiester bond
d. Hydrogen bond
Answer: The correct answer is option (b), Glycosidic bond
Explanation: Glycosidic bonds are the chemical connections between monosaccharide units in polysaccharides. Peptide bonds connect amino acids in proteins, phosphodiester bonds connect nucleotides in DNA and RNA, and hydrogen bonds are weaker interactions that stabilise the structure of molecules.
Here is a table for all the important topics from the chapter:
Below are the chapter-wise solutions:
The different types of structures of biomacromolecules given in Chapter 9 of NCERT Solutions for Class 11 Biology are:
The important topics of NCERT Solutions for Class 11 Biology Chapter 9 are:
Nucleic acids (DNA and RNA) are nucleotide polymers, composed of a sugar, phosphate group, and nitrogenous base (A, T/U, G, C). DNA is double-helix, whereas RNA is typically single-stranded. They carry and transfer genetic information, with DNA coordinating protein synthesis and RNA helping in transcription and translation. Their structure allows replication, gene expression, and heredity in living things.
Vitamins serve as coenzymes or coenzyme precursors, facilitating enzymatic reactions during metabolism. Vitamins assist in energy production, immune function, cell growth, and repair. Vitamins are either water-soluble (B-complex, C) or fat-soluble (A, D, E, K), with each having a unique biochemical function.
Biomolecules possess the following features:
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