Biomolecules — Page 3 | JEE Chemistry

Q21

The pyrimidine bases present in DNA are

A cytosine and adenine

B cytosine and guanine

C cytosine and thymine

D cytosine and uracil

Correct Answer

Option C

Solution

DNA contains cytosine and thymine as pyrimidine bases and guanine and adenine as purine bases.

Q22

The secondary structure of a protein refers to

A

\alpha

-helical backbone

B hydrophobic interactions

C sequence of

\alpha

-amino acids

D fixed configuration of the polypeptide backbone

Correct Answer

Option A

Solution

The secondary structure of a protein refers to the shape in which a long peptide chain can exist.

There are two different conformations of the peptide linkage present in protein, these are $\alpha$ -helix and $\beta$ -conformation.

The $\alpha$ -helix always has a right handed arrangement.

In $\beta$ -conformation all peptide chains are streched out to nearly maximum extension and then laid side by side and held together by intermolecular hydrogen bonds.

The structure resembles the pleated folds of drapery and therefore is known as $\beta$ -pleated sheet.

Q23

\alpha

-D-(+)-glucose and

\beta

-D-(+)-glucose are

A conformers

B epimers

C anomers

D enantiomers

Correct Answer

Option C

Solution

Since

\alpha - D - \left( + \right) - \,\,

glucose and

\beta - D - \left( + \right)\,\,

glucose differ in configuration at

C-1

atom so they are anomers. NOTE : Anomers are those diastereomers that differ in configuration at

C-1

atom. i.e.,

(c)

in the correct answer.

Q24

The two functional groups present in a typical carbohydrate are

A -OH and -COOH

B -CHO and -COOH

C > C = O and - OH

D - OH and -CHO

Correct Answer

Option D

Solution

NOTE : Glucose is considered as a typical carbohydrate which contains

-CHO

and

-OH

group.

Q25

Biuret test is not given by

A carbohydrates

B polypeptides

C urea

D proteins

Correct Answer

Option A

Solution

Biuret test produces violet colour on addition of dilute

CaS{O_4}

to alkaline solution of a compound containing perptide linkage.

Polypeptides, proteins and urea have - (peptide) linkage while carbohydrates have glycosidic linkages.

So, test of carbohydrates should be different from that of other three.

Q26

Which one of the following statements is correct ?

A All amino acids except lysine are optically active

B All amino acids are optically active

C All amino acids except glycine are optically active

D All amino acids except glutamic acid are optically active

Correct Answer

Option C

Solution

With the exception of glycine all the

19

other common amino acids have a uniquely different functional group on the central tetrahedral alpha carbon.

Q27

Synthesis of each molecule of glucose in photosynthesis involves:

A 10 molecules of ATP

B 8 molecules of ATP

C 6 molecules of ATP

D 18 molecules of ATP

Correct Answer

Option D

Solution

6C{O_2} + 12NADPH + 18ATP

+ 6RuBP

\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \to {C_6}{H_{12}}{O_6} + 12NADP + 18ADP

+ 6RuBP + 18P One molecule of glucose is formed from 6CO2 by utilising 18ATP and 12NADPH.

Q28

Which one of the following bases is not present in DNA?

A Cytosine

B Thymine

C Quinoline

D Adenine

Correct Answer

Option C

Solution

DNA

contains adenine (A), thymine (T), guanine (G) and cytosine (C) bases. So quinoline is not present in

DNA.

Q29

Which of the vitamins given below is water soluble?

A Vitamin D

B Vitamin E

C Vitamin K

D Vitamin C

Correct Answer

Option D

Solution

Water-soluble vitamins dissolve in water and are not stored by the body. The water soluble vitamins include the vitamin

B

-complex group and vitamin

C.

Q30

Thiol group is present in :

A Cytosine

B Cystine

C Cysteine

D Methionine

Correct Answer

Option C

Solution

Among

20

naturally occuring amino acids ''Cysteine'' has' $-$

SH'

or thiol functional group.