Biomolecules: Important Questions

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Very Short Answer Type Questions (1 Marks Question)

Ques. What is meant by Reducing sugars? (All India 2010)

Ans. Reducing sugar are the sugars that contain aldehydic or Ketonic groups in the form of Hemiacetal and Hemiketal. Reducing sugar can reduce Tollen’s reagent & it can also reduce the Fehlmg's solution.

Ques. Name a water-soluble vitamin that is a powerful antioxidant. Give the name of its natural source. (Comptt. Delhi 2012)

Ans. The name of a water-soluble vitamin is Vitamin C. The name of the natural source of Vitamin C is Amla.

Ques. What is a Glycosidic linkage? (Delhi 2013)

Ans. Glycosidic linkage is the process When two monosaccharide units are joined together through an oxide or etheral linkage that is formed by the loss of a water molecule. Hence, The linkage between monosaccharide units through oxygen is called Glycosidic Linkage.

Ques. Write the name of the linkage joining two amino acids. (All India 2013)

Ans. The name of the linkage that joins two amino acids is Peptide Linkage.

Ques. Name the deficiency diseases resulting from a lack of Vitamin E & A in the diet. (Comptt. Delhi 2013)

Ans. The deficiency of Vitamin E results in Sterility & the deficiency of Vitamin A results in Xerophthalmia.

Ques. Mention one important function of nucleic acids in our body. (Comptt. All India 2013)

Ans. The function of nucleic acid is to control the transmission of hereditary characteristics from one generation to another one.

Ques. Define Peptide Linkage. (Comptt. All India 2014)

Ans. Peptide linkage is an amid a linkage that is formed between -COOH group of ono a

-amino acid by the loss of a water molecule.

The bond – CO – NH is called the Peptide Linkage.

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Short Answer Type Questions (2 marks)

Ques. Name the essential & non-essential amino acids found in human food? Give an example of each. (Delhi 2009)

Ans. The Essential Amino Acids:

The acids that cannot be synthesized by the human body are called essential amino acids. Consequently, they must be supplied to the diet.

Examples: Leucine, Valine, etc.

The Non-essential Amino Acids:

Non-Essential Amino Acids are acids that can be easily synthesized by the human body. Consequently, they can be present in the diet or they can not be present in the diet.

Examples: Alanine, Glycine, etc.

Ques. State clearly what is known as Nucleosides & Nucleotides? ( Delhi 2009)

Ans. Nucleoside:

Nucleoside encompasses only two primary elements of nucleic acids, one is The nitrogenous base & the other is A pentose sugar. During the formation of position -1 of the pyrimidine or position, -9 of the purine moiety is linked with the C 1 of the sugar (mainly ribose or deoxyribose) through a β-linkage.

Nucleotides: Nucleotides encompass all three vital components of nucleic acids. These three components are the Phosphoric acid group, A Pentose sugar & the Nitrogen base. They can be formed by esterification of C₅ ‘- OH of the nucleoside sugar with phosphoric acid.

Ques. Name the bases present in RNA. Write the name of the one base that is not present in DNA? (Delhi 2009)

Ans. The four bases presented in RNA:

• Adenine (A)
• Guanine (G)
• Pyrimidine – Uracil (U)
• Cytosine ( C)

The base that is not presented in DNA:

• Uracil

Ques. Write the main structural difference between DNA & RNA. Write the name of those bases which are common in DNA & RNA. (All India 2009)

Ans. Difference between DNA & RNA

Common bases in DNA & RNA:

• Adenine (A)
• Cytosine ( C)
• Guanine (G)

Ques. (A) name the only vitamin which can be synthesized in our body. Write the name of a disease that is caused due to the deficiency of this vitamin.

(B) State two functions of carbohydrates. (Comptt. All India 2012)

Ans. (A) The only vitamin that can be synthesized is Vitamin B12. the disease caused due to the deficiency of Vitamin B12 is Pernicious Anaemia.

(B) the two functions of carbohydrates:

• Carbohydrate provides energy for the functioning of living organisms. These carbohydrates are glucose, starch & glycogen, etc.
• The carbohydrate Cellulose is used for making furniture & houses in the form of wood.

Ques.(1) Deficiency of which vitamin causes night-blindness?

(2) Write the name of the base that is found as a nucleotide of RNA only.

(3) Glucose on reaction with HI gives n-hexane. What does it represent about the structure of glucose? (Delhi 2014)

Ans. (1) The deficiency of Vitamin A causes Night-blindness.

(2) Uracil is the name of the base that is found as a nucleotide of RNA.

(3) the glucose when reacted with HI gives n-hexane. It represents the open structure of glucose.

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Long Answer Type Questions (3 marks)

Ques. Write the difference between the following:

1. Amylose & Amylopectin
2. Peptide linkage Glycosidic linkage
3. Fibrous proteins & Globular Proteins

Or, Write a chemical reaction to indicate that the open structure of D-Glucose contains the following:

1. Straight chain
2. Five Alcohol Groups
3. Aldehyde as Carbonyl group

(CBSE Delhi 2019)

Ans. 1) Difference between Amylose & Amylopectin

2) Difference between Peptide Linkage & Glycosidic Linkage

3) Difference between Fibrous protein & Globular Protein

Or

1. When glucose is prolonged heated with HI & red P at 100° C, it gives n-hexane, & shows the straight-chain structure of glucose.
2. Glucose does react with acetic anhydride when anhydrous zinc chloride is presented and it forms glucose pentaacetate. It confirms the presence of five-OH groups in the glucose molecule and forms the pentaacetate.
3. Glucose reacts with hydrogen cyanide and forms glucose cyanohydrin. It shows that glucose contains a carbonyl group (> C= 0)

Thus, glucose gets oxidized to six carbon gluconic acid when treated with a mild oxidizing agent like Br₂ water. It indicates that the carbonyl group that is presented in glucose is an aldehyde (-CHO).

Ques. What do you understand by the primary structure & secondary structure of proteins? (Delhi 2009)

Ans. The primary structure of proteins:

Proteins can have one or more polypeptide chains. Each of the polypeptides has amino acids linked with each other in a specific classification is known as the primary structure of the protein. The primary structure can be determined by the successive hydrolysis of the structure with enzymes and mineral acids.

The secondary structure of the protein

The secondary structure of the protein shows how the polypeptide chains are arranged or folded. polypeptide chains confirm to assume as a result of hydrogen bonding is called the secondary structure of the protein. It arises from the plane geometry of the group of the peptide bonds.

It depends upon the size of the R groups, so the two different structures are possible :

• a-helix structure

The intramolecular H-bonds that are present between the C=0 of one amino acid & N-H of the fourth amino acid. It has a spiral structure.

• β-pleated sheet structure

All the polypeptide chains are stretched out to the, nearly maximum extension & after that, it is laid down by side in a zigzag manner to form a sheet that is flat in shape. chains chain is held to the two neighboring chains by a bond of hydrogen.

Ques. Define tin following terms with suitable examples of each. (CBSE AI 2019)

• Anomers
• Essential Amino Acids
• Denaturation of Protein

Ans. Anomers

Anomers are carbohydrates that differ in configuration at the Glycosidic carbon. (I.e. C1 in aldoses & C2 is found in ketoses).

Examples: a – D – glucose, β-D-glucose.

Essential Amino Acids

These acids are the acids that are not made by the human body. The amino acids must have to be supplied into our diet.

Examples: Valine, leucine.

Denaturation of protein

The denaturation of protein is the process that changes the nactive conformation of the protein. The denaturation of protein can be caused by the changes in pH, temperature and the presence of salts in certain chemical agents. During the process of denaturation, the protein molecules uncoil from an ordered and certain confirmation and then the protein precipitates from a three-dimensional structure.

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Very Long Answer Type Questions (5 marks)

Ques. Describe the following:

• Choose the one which is a polysaccharide:

Starch, Maltose, fructose, glucose (CBSE 2015, 2014)

• Write the difference between native protein & denatured protein?
• Write the name of the vitamin which is responsible for the coagulation of blood.

Ans.

• Starch is a polysaccharide.

• Difference between native protein and denatured protein

Native protein is found in a biological system along with a different three-dimensional structure & in biological activity.

Whereas the denatured protein loses its biological activity by some certain physical or chemical treatment. The treatment such as pH changes, temperature, the presence of certain salt or chemical agents is popularly known as denaturation.

• Vitamin K is the vitamin that is responsible for the coagulation of blood.

Ques. How do you explain the presence of an aldehydic group on a glucose molecule?

Ans. The glucose immediately reacts with hydroxylamine and forms a monoxime and then it adds one molecule of hydrogen cyand to give it to the cyanohydrin.

Here is how;

Thus, it contains a carbonyl group that can be an aldehyde or a ketone. When doing mold oxidation with bromine water, the glucose gives the gluconic acid. This gluconic acid is a carboxylic acid that contains six carbon atoms in it.

It indicates that the carbonyl group is present in glucose. The group is aldehydic.

Ques. Describe the terms D- & L- configuration used for sugars. Explain it with examples.

Ans. The sugars are distributed into two families:

• The D-family
• The L-family

Both the families have definite configurations.

Both these configurations are represented concerning glyceraldehyde as per the standard.

It can be presented in two forms

The configuration D- has -OH which is attached to the carbon adjacent to -CH₂OH On the right whereas the L- configuration has -OH which is attached to the carbon adjacent to -CH₂OH on the left.

The sugars there are called D- or -L based on the configuration. It depends on the fact if the molecule is related to D-glyceraldehydes or the L-glyceraldehydes. It has been found that all the sugars that are occurred naturally belong to D-series.

Example: D-glucose, D-ribose and D-fructose.

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