Chemistry

Biomolecules

Question:

How do you explain the presence of five -OH groups in glucose molecule?

Answer:

Glucose gives penta-acetyl derivative on acetylation with acetic anhydride.
ncert-exemplar-problems-class-12-chemistry-biomolecules-25
This confirms the presence of five -OH groups.

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Biomolecules

Q 1.

What are essential and non-essential amino acids? Give two examples of each type.

Q 2.

Aldopentoses named ribose and 2-deoxyribose are found in nucleic acids.
What is their relative configuration?

Q 3.

Assertion (A): Deoxyribose, C5H10O4 is not a carbohydrate.
Reason (R): Carbohydrates are hydrates of carbon so compounds which follow Cx(H2O)y formula are carbohydrates.

Q 4.

During curdling of milk, what happens to sugar present in it?

Q 5.

Three structures are given below in which two glucose units are linked. Which of these linkages between glucose units are between C1 and C4 and which linkages are between C1 and C6?
ncert-exemplar-problems-class-12-chemistry-biomolecules-12

Q 6.

Describe the term D- and L-configuration used for amino acids with examples.

Q 7.

When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?

Q 8.

What is glycogen? How is it different from starch?

Q 9.

How do you explain the presence of all six carbon atoms in glucose in a straight chain?

Q 10.

Assertion (A): Vitamin D can be stored in our body.
Reason (R): Vitamin D is fat soluble vitamin.

Q 11.

Which monosaccharide units are present in starch, cellulose and glycogen and which linkages link these units?

Q 12.

Why does compound (A) given below not form an oxime?
ncert-exemplar-problems-class-12-chemistry-biomolecules-26

Q 13.

Why are vitamin A and vitamin C essential to us? Give their important sources.

Q 14.

What is the difference between a nucleoside and a nucleotide?

Q 15.

Which of the following terms are correct about enzyme?
(a) Proteins (b) Dinucleotides
(c) Nucleic acids (d) Biocatalysts

Q 16.

The letters ' D ' or ' L' before the name of a stereoisomer of a compound indicate the correlation of configuration of that particular stereoisomer.
ncert-exemplar-problems-class-12-chemistry-biomolecules-21
This refers to their relation with one of the isomers of glyceraldehydes. Predict whether the following compound has ‘D' or ‘L' configuration.

Q 17.

Assertion (A): β-glycosidic linkage is present in maltose.
ncert-exemplar-problems-class-12-chemistry-biomolecules-39
Reason (R): Maltose is composed of two glucose units in which C-l of one glucose unit is linked to C-4 of another glucose unit.

Q 18.

Where does the water present in the egg go after boiling the egg?

Q 19.

What type of bonding helps in stabilising the α-helix structure of proteins?

Q 20.

What is the effect of denaturation on the structure of proteins?

Q 21.

Which of the following are purine bases?
(a) Guanine (b) Adenine (c) Thymine (d) Uracil

Q 22.

Under what conditions glucose is converted to gluconic and saccharic acid?

Q 23.

Sucrose is dextrorotatory but the mixture obtained after hydrolysis is laevorotatory. Explain.

Q 24.

Carbohydrates are essential for life in both plants and animals. Name the carbohydrates that are used as storage molecules in plants and animals, also name the carbohydrate which is present in wood or in the fibre of cotton cloth.

Q 25.

How are vitamins classified? Name the vitamin responsible for the coagulation of blood.

Q 26.

In disaccharides, if the reducing groups of monosaccharides, i.e., aldehydic or ketonic groups are bonded, these are non-reducing sugars. Which of the following disaccharide is a non-reducing sugar?
ncert-exemplar-problems-class-12-chemistry-biomolecules-5

Q 27.

Carbohydrates are classified on the basis of their behaviour on hydrolysis and also as reducing or non-reducing sugar. Sucrose is a .
(a) monosaccharide (b) disaccharide
(c) reducing sugar (d) non-reducing sugar

Q 28.

ncert-exemplar-problems-class-12-chemistry-biomolecules-23

Q 29.

Assertion (A): In presence of enzyme, substrate molecule can be attacked by the reagent effectively.
Reason (R): Active sites of enzymes hold the substrate molecule in a suitable position.

Q 30.

Write two main functions of carbohydrates in plants.

Q 31.

How do enzymes help a substrate to be attacked by the reagent effectively?

Q 32.

Assertion (A): All naturally occurring a-amino acids except glycine are optically active.
Reason (R): Most naturally occurring amino acids have L-configuration.

Q 33.

Which of the following carbohydrates are branched polymer of glucose?
(a) Amylose (b) Amylopectin (c) Cellulose (d) Glycogen

Q 34.

What happens when D-glucose is treated with . the following reagents.
(i)HI (ii) Bromine water (iii) HNO3

Q 35.

ncert-exemplar-problems-class-12-chemistry-biomolecules-15

Q 36.

Amino acids behave like salts rather than simple amines or carboxylic acids. Explain.

Q 37.

Structures of glycine and alanine are given below. Show the peptide linkage in glycylalanine.
ncert-exemplar-problems-class-12-chemistry-biomolecules-30

Q 38.

What are the expected products of hydrolysis of lactose?

Q 39.

What do you understand by the term glycosidic linkage?

Q 40.

In nucleoside a base is attached at 1′ position of sugar moiety. Nucleotide is formed by linking of phosphoric acid unit to the sugar unit of nucleoside. At which position of sugar unit is the phosphoric acid linked in a nucleoside to give a nucleotide?

Q 41.

Protein found in a biological system with a unique three dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to a physical change like change in temperature or a chemical change like, change in pH, denaturation of protein takes place. Explain the cause.

Q 42.

What are glycosidic linkages? In which type of biomolecules are they present?

Q 43.

Match the vitamins given in Column I with the deficiency disease they cause given in Column II.
ncert-exemplar-problems-class-12-chemistry-biomolecules-37

Q 44.

Assertion (A): Glycine must’be taken through diet.
Reason (R): It is an essential amino acid.

Q 45.

The melting points and solubility of amino acids in water are generally higher than those of corresponding haloacids. Explain.

Q 46.

What are monosaccharides ?

Q 47.

What are reducing sugars?

Q 48.

Classify the following into monosaccharides and disaccharides. Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose.

Q 49.

What is the basic structural difference between starch and cellulose?

Q 50.

How do you explain the amphoteric behaviour of amino acids?