Chemistry

Biomolecules

Question:

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

Answer:

Enzymes are biocatalysts. They reduce the magnitude of activation energy by providing alternative path. In the hydrolysis of sucrose, the enzyme sucrase reduces the activation energy from 6.22 kJ mol-1 to 2.15 kJ mol-1. As a result, enzyme catalysed reactions occur at a much faster rate than the ordinary chemicdl reactions using conventional catalysts.

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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.

Name the linkage connecting monosaccharide units in polysaccharides.

Q 3.

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 4.

Why must vitamin C be supplied regularly in diet?

Q 5.

Match the following enzyme given in Column I with the reactions they catalyse given in Column II.
ncert-exemplar-problems-class-12-chemistry-biomolecules-38

Q 6.

Name the sugar present in milk. How many monosaccharide units are present in it? What are such oligosaccharides called?

Q 7.

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

Q 8.

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

Q 9.

What are reducing sugars?

Q 10.

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 11.

In fibrous proteins, polypeptide chains are held together by
(a) van der Waals forces (b) disulphide linkage
(c) electrostatic forces of attraction (d) hydrogen bonds

Q 12.

What are the common types of secondary structure of proteins?

Q 13.

How do you explain the absence of aldehyde group in the pentaacetate of D-glucose?

Q 14.

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

Q 15.

What are enzymes?

Q 16.

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 17.

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

Q 18.

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 19.

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 20.

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 21.

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

Q 22.

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 23.

What are nucleic acids ? Mention their two important functions.

Q 24.

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

Q 25.

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

Q 26.

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 27.

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

Q 28.

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

Q 29.

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

Q 30.

What are the expected products of hydrolysis of lactose?

Q 31.

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

Q 32.

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

Q 33.

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

Q 34.

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

Q 35.

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 36.

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

Q 37.

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

Q 38.

The two strands in DNA are not identical but are complementary. Explain.

Q 39.

Optical rotations of some compounds along with their structures are given below which of them have D configuration.
ncert-exemplar-problems-class-12-chemistry-biomolecules-10

Q 40.

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

Q 41.

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

Q 42.

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

Q 43.

Glucose or sucrose are soluble in water but cyclohexane and benzene (simple six membred ring compounds) are insoluble in water Explain.

Q 44.

What do you understand by the term glycosidic linkage?

Q 45.

What is glycogen? How is it different from starch?

Q 46.

Structure of a disaccharide formed by glucose and fructose is given below. Identify anomeric carbon atoms in monosaccharide units.
ncert-exemplar-problems-class-12-chemistry-biomolecules-11

Q 47.

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

Q 48.

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

Q 49.

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

Q 50.

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