CBSE Important Questions Class 12 Chemistry Chapter 14

Important Questions Class 12 Chemistry Chapter 14

Important Questions for CBSE Class 12 Chemistry Chapter 14 – Biomolecules

Important Questions Class 12 Chemistry Chapter 14 are prepared by the subject experts after consulting the questions of the past years and the updated CBSE Syllabus. Several questions from the CBSE Sample Papers that are important from the exam perspective are also included. Chemistry Class 12 Chapter 14 Important Questions will help students revise the important topics and practise more questions to get the highest score in the exam.

CBSE Class 12 Chemistry Chapter-14 Important Questions 

Study Important Questions for Class 12 Chemistry Chapter 14 – Biomolecules

Very Short Answer  Questions (1 Mark)

Q.1. Give an example of a storage polysaccharide found in the liver and muscles of animals.

Ans. Glycogen is an example of a storage polysaccharide found in the livers and muscles of  animals.

Q.2. Why do carbohydrates often act as reducing agents?

Ans. Carbohydrates act as reducing agents because of the presence of aldehydic groups (- CHO) and ketol groups (- CO-CH2OH) in them. Carbohydrates containing aldehyde groups are glucose, mannose, and galactose, and carbohydrates containing ketol groups are fructose.

Q.3. What is the name of the monomer of protein?

Ans. Amino acid is the monomer of protein.

Q.4. Which is the simplest form of amino acid that is optically active as well?

Ans. Alanine is the simplest form of amino acid that is optically active as well.

Q.5. Write down the name of the amino acid that does not show any optical activity.

Ans. Among the various types of amino acids, glycine is the only one that does not show any optical activity.

Q.6. Which enzyme is responsible for transforming maltose into glucose?

Ans. Maltase is responsible for transforming maltose into glucose. It is released by the colon during digestion. 

Q.7. Give two examples of nucleic acids.

Ans. DNA and RNA are two examples of nucleic acids. 

Q.8. How are DNA and RNA held together?

Ans. The phosphodiester bond holds the monomers of DNA and RNA together.

Q.9. A child is diagnosed with a bone deformity. What kind of medication should he/she be given initially?

Ans. Vitamin D and calcium are essential for healthy bone growth. The deformity in the child, therefore, may have been caused by the deficiency of these two elements. So, vitamin D and calcium supplements can be given to the child initially.

Q.10. What is meant by DNA fingerprinting?

Ans. DNA fingerprinting is the study of different DNA profiles and comparing them. Any piece of DNA  collected from the crime scene is compared to the DNA collected from the suspect to determine whether he is the real culprit or not. This technique is also effective in determining the biological parents of a baby.

Q.11. What is the significance of vitamin K in the coagulation of blood?

Ans. Vitamin K helps in the coagulation of blood by synthesising the blood-clotting protein prothrombin.

Q.12. Vitamin B enriched foods must be included in our diet chart. Why is vitamin B required?

Ans. Vitamin B is crucial for the processes of metabolism, the formation of new blood cells, and maintaining  healthy skin. So, we need vitamin B enriched food to let natural activities run smoothly.

Q.13. Write down the industrial preparation of glucose.

Ans. Glucose is prepared in industries by the process of hydrolysis. Starch is heated with dilute H2SO4 at 393 K temperature to produce glucose from it.

Q.14. Write down the name of the enzyme that initiates the metabolism of glucose.

Ans. Hexokinase is the enzyme responsible for initiating the metabolism process of glucose.

Q.15. Give some examples of oligosaccharides.

Ans. Sucrose, lactose, and maltose are some examples of oligosaccharides.

Q.16. Mention one structural difference between oligosaccharides and polysaccharides.

Ans. Oligosaccharides are made up of a limited number of monosaccharides. This number of saccharide monomers varies between three and ten. Polysaccharides are lengthy chains of monosaccharides linked together with glycosidic connections.

Q.17. What is the function of protein in the human body?

Ans. The functions of proteins are as follows:

  • Protein is essential for repairing damaged cells in our bodies.
  • Protein helps in the development of organs, muscles, skin, and hormones.

Q.18. Mention the names of any two nitrogenous bases that are held together by a double hydrogen bond.

Ans. Adenine and thymine are two nitrogenous bases found in DNA that are held together by a double hydrogen bond.

Q.19. Which nucleic acid is crucial for the protein synthesis of our cells?

Ans. Ribonucleic acid, or RNA, is crucial for the protein synthesis of our cells.

Q.20. The two strands of DNA are not identical but complementary. Comment.

Ans. The strands are made up of  different nitrogenous bases. Adenine and cytosine form hydrogen bonds with thymine and guanine, respectively. So, on one strand, when there is adenine, the opposite side of the other strand must contain thymine or vice versa. Similarly, when cytosine is present on one strand, guanine must be present on the other side.

Short Answer  Questions (2 Marks)

Q.1. What are vitamins? Classify them on the basis of their solubility.

Ans. An organism needs different types of nutrients to run its metabolic activities. It acquires nutrients mainly through food. One of these nutrients is a vitamin. Deficiency in vitamins often leads to diseases like scurvy, rickets, beriberi, etc. In addition to that, various types of skin diseases can be caused by an inadequacy of vitamins in the body.

Based on their solubility, vitamins can be divided into two categories: vitamins that are soluble in fat, and vitamins that are soluble in water. Fat-soluble vitamins include A, D, E, and K, whereas all the vitamins B and  C are examples of vitamins soluble in water.

Q.2. What are essential amino acids and non-essential amino acids? Give examples.

Ans. Amino acids are crucial for the growth and development of the body. However, the body cannot synthesise every type of amino acid. Those amino acids that cannot be produced in the body and are acquired through food are called essential amino acids. For example, valine and tryptophan. The amino acids that the body can produce are known as non-essential amino acids. For example, glycine and glutamic acid.

Q.3. Why is vitamin C readily absorbed in our body?

Ans. Though vitamin C is extremely crucial for the body, it gets expelled from it through urine immediately due to its high solubility in water. So, the body absorbs the vitamin quickly to utilise it for nutrition.

Q.4.What are the definitions of hypervitaminosis and avitaminosis?

Ans: Hypervitaminosis refers to the condition when there is an excessive presence of vitamins in the body, mainly vitamins A and D. Hypervitaminosis can be caused by an excess of vitamin A and vitamin D-rich foods, as well as long-term acne treatments.Vision difficulties, skin diseases, and bone discomfort are common symptoms of it. If it is not treated quickly, it can harm the liver and brain eventually.

Avitaminosis is a condition caused by the deficiency of one or more vitamins in the body. As vitamins are essential for growth, such diseases are common in infants and pregnant women who do not get adequate vitamins. Severe diarrhoea or excessive sweating can also lead to such illnesses.

Q.5. Mention the structures of the two possible dipeptides that can be formed by glycine and alanine.

Ans. Dipeptide bonds formed by glycine (Gly) and alanine (Ala) can be symmetrical or asymmetrical. The symmetrical bond can be expressed as GlyGly and AlaAla; and asymmetrical bonds can be written as GlyAla and GlyAla.

 Long Answer  Questions (3 Marks)

Q.1. How many types of carbohydrates are there? Mention their names.

Ans. Carbohydrates can be divided into four categories based on the presence of a certain number of sugar molecules, namely, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. These categories can be further divided in the following manner:

  1. Monosaccharides (having one sugar molecule)
    1. Glucose
    2. Fructose
    3. Galactose
  2. Disaccharides (having two sugar molecules)
    1. Sucrose
    2. Lactose
    3. Maltose
  3. Oligosaccharides (having three sugar molecules)
    1. Raffinose
    2. Stachyose
  4. Polysaccharides (having four sugar molecules)
    1. Starch
    2. Glycogen
    3. Cellulose

Q.2. (i)How many chiral carbon atoms are present in D(+) glucose?

Ans. (i) Chiral carbons are those carbon atoms that contain four different atoms or groups.

 In D(+) glucose, four such carbon atoms are present.

(ii) Write the name of the enantiomer of D-glucose.

Ans. Glucopyranose β-D-(+) is the enantiomer of D-glucose.

(iii) What is the meaning of the (+) sign in the name D(+) glucose?

Ans. A compound’s isomers can be dextrorotatory or levorotatory. The dextrorotatory isomers are denoted by the plus (+) sign, while the levorotatory isomers are denoted by the minus (−) sign. So, the (+) sign in the name of D(+) glucose denotes that it is a dextrorotatory isomer of D-glucose.

Q.3.Proteins are both fibrous and globular.. How are they different from each other?

Ans. The differences between fibrous and globular are discussed below: 

Fibrous Globular
  1. These protein molecules have a long, fibre-like structure because of the parallel arrangements of polypeptide chains along a single axis.
  1. The structure of these protein molecules resembles spheres or cigars.
  1. Their main function is to provide the structures of various cells.
  1. Their main function is to perform specific biological activities.
  1. They are not soluble in water.
  1. They are soluble in acid, base, alcohol as well as water.

Q.4.(i). Write down the nitrogenous bases present in DNA.

Ans. (i)The four nitrogenous bases present in the DNA are:

  1. Adenine
  2. Thymine
  3. Guanine
  4. Cytosine

 RNAs also contain the same nitrogenous bases that can be found in DNA, except for one. (ii)What is the name of the base? Which nucleotide base is present in RNAs but not in DNAs?

Ans. Thymine is the nitrogenous base absent in RNAs. Instead of thymine, uracil is present in RNAs, whereas it is absent in DNAs.

(iii) Mention one function of each: DNA and RNA.

Ans. The function of DNA: It carries the genetic code that is transmitted through genes from one generation to another.

The function of RNA: It facilitates the process of translation of DNA.

Q.5. (i) What is meant by the denaturation of protein molecules?

Ans. Denaturation refers to the destruction of the natural properties of protein molecules due to exposure to extreme acidity, extreme basicity, radiation, heat, or salts. In the worst case, the cells containing protein molecules may die.

(ii) Define the term “specificity” of an enzyme.

Ans. The specificity of an enzyme refers to its ability to choose a specific substrate to work on. Only a few enzymes show this property. Specificity can be of four types, such as absolute specificity, group specificity, linkage specificity, and stereochemical specificity.

FAQs (Frequently Asked Questions)

1. Explain the reason for the stability of the -helical structure of proteins.

The -helical structure of proteins is stable because of the presence of hydrogen bonds in them. The building block of proteins is the amino acid. An amino acid’s -NH- groups form hydrogen bonds with the >C=O groups on their adjacent sides, giving the amino acid a helix-like structure and making it stable.

2. Explain the reason for the amphoteric behaviour of amino acids.

Amino acid molecules consist of a carboxyl group and an amino group. These carboxyl groups are acidic in nature, whereas the amino groups are basic. In the aqueous solution, the carboxyl group releases a proton that is received by the amino group.  Thus, they neutralise each other’s effect. However, an amino acid also reacts with bases in its zwitterionic form despite being a base itself. Thus, it shows amphoteric behaviour.

3. What causes the inactivity of amylase in the stomach?

Amylase enzymes cannot work in an acidic environment. In the stomach, extreme acidity is produced because of the secretion of hydrochloric acid, which causes the denaturation and change in the shape of the amylase enzymes. This is the reason that the given enzyme becomes inactive in the stomach.

4. Write the Zwitter ionic form of glycine.

The Zwitter ionic form of glycine is: NH3+−CH2−COO–.

5. What is the reason that glucose does not react with sodium hydrogen sulphite?

Glucose does not react with sodium hydrogen sulphite because it does not contain any free aldehyde group to complete the reaction and produce any bisulphite addition products.