Chemistry

Biomolecules

Question:

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.

Answer:

Carbohydrate that are used as storage molecules in plants and animals are as follows
(i) Plant contains mainly starch, cellulose, sucrose, etc.
(ii) Animal contain glycogen in their body. So, glycogen is also known as animal starch. Glycogen is present in liver, muscles and brain when body needs glucose, enzyme breaks glycogen down to glucose.
(iii) Cellulose is present in wood, and fibre of clothes.

previuos
next

Biomolecules

Q 1.

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 2.

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

Q 3.

Name the linkage connecting monosaccharide units in polysaccharides.

Q 4.

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

Q 5.

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

Q 6.

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

Q 7.

What are the common types of secondary structure of proteins?

Q 8.

What are enzymes?

Q 9.

Which sugar in called invert sugar? Why is it called so?

Q 10.

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

Q 11.

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

Q 12.

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

Q 13.

Differentiate between globular and fibrous proteins.

Q 14.

Why must vitamin C be supplied regularly in diet?

Q 15.

Why cannot Vitamin C be stored in our body?

Q 16.

What is glycogen? How is it different from starch?

Q 17.

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

Q 18.

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

Q 19.

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

Q 20.

What is the basic structural difference between starch and cellulose?

Q 21.

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

Q 22.

Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ mol-1, while hydrolysis is catalysed by the enzyme sucrase. Explain.

Q 23.

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

Q 24.

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 25.

Which of the following pairs represents anomers?
ncert-exemplar-problems-class-12-chemistry-biomolecules-3
ncert-exemplar-problems-class-12-chemistry-biomolecules-4

Q 26.

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 27.

α-Helix is a secondary structure of proteins formed by twisting of polypeptide chain into right handed screw like structures. Which type of interactions are responsible for making the a-helix structure stable?

Q 28.

Some enzymes are named after the reaction, where they are used. What name is given to the class of enzymes which catalyse the oxidation of one substrate with simultaneous reduction of another substrate?

Q 29.

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

Q 30.

Write two main functions of carbohydrates in plants.

Q 31.

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

Q 32.

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 33.

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

Q 34.

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

Q 35.

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 36.

How do you explain the presence of an aldehydic group in a glucose molecule?

Q 37.

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 38.

What are the expected products of hydrolysis of lactose?

Q 39.

What are the hydrolysis products of (i) sucrose, and (ii) lactose?

Q 40.

What are the different types of RNA found in the cell?

Q 41.

Which of the following monosaccharides are present as five membered cyclic structure (foranose structure)?
(a) Ribose (b) Glucose (c) Fructose (d) Galactose

Q 42.

Monosaccharides contain carbonyl group hence are classified, as aldose or ketose. The number of carbon atoms present in the monosaccharide molecule are also considered for classification. In which class of monosaccharide will you place fructose?  

Q 43.

What are nucleic acids ? Mention their two important functions.

Q 44.

What is the difference between a nucleoside and a nucleotide?

Q 45.

Write the important structural and functional differences between DNA and RNA.

Q 46.

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

Q 47.

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

Q 48.

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 49.

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

Q 50.

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