Biomolecules

NEET Chemistry · 137 questions · Page 13 of 14 · Click an option or "Show Solution" to reveal answer

Q121

Compound A gives D-Galactose and D-Glucose on hydrolysis. The compound A is :

A Amylose

B Sucrose

C Maltose

D Lactose

Correct Answer

Option D

Solution

Lactose : It is a disaccharide of $\beta$ -D-Galactose and $\beta$ -D-Glucose with C1 of galactose and C4 of glucose link.

Lactose : $\beta$ -D-Galactose + $\beta$ -D-Glucose

Q122

Which of the following statements is not true about sucrose?

A The glycosidic linkage is present between C1 of

\alpha

-glucose and C1 of

\beta

-fructose

B It is also named as invert sugar

C It is a non reducing sugar

D On hydrolysis, it produces glucose and fructose

Correct Answer

Option A

Solution

The glycosidic linkage is present between C1 of $\alpha$ -D-glucose and C2 of $\beta$ -D-fructose.

Q123

Complete hydrolysis of cellulose gives

A D-ribose

B D-glucose

C L-glucose

D D-fructose

Correct Answer

Option B

Solution

Cellulose is a linear polymer of $\beta$

- D -

glucose in which

{C_1}

of one glucose unit is connected to

{C_4}

of the other through

\beta - D

glucosidic linkage. It does not undergo hydrolysis easily. However on heating with dilute

{H_2}S{O_4}

under pressure. It does undergo hydrolysis to give only

D-

glucose.

\left( {{C_6}{H_{10}}{O_5}} \right)n + n{H_2}O\overset{{\,H + }}\longrightarrow \mathop {n{C_6}{H_{12}}{O_6}}\limits_{D - Glu\cos e}

Q124

Which of the following statements is not true about RNA?

A It controls the synthesis of protein

B It is present in the nucleus of the cell

C It usually does not replicate

D It has always double stranded

\alpha

-helix structure

Correct Answer

Option D

Solution

RNA has a single standard helix structure. DNA has a double standard helix structure

Q125

Which of the following compounds can be detected by Molisch’s test ?

A Nitro compounds

B Sugars

C Amines

D Primary alcohols

Correct Answer

Option B

Solution

Molisch's Test : This is a general test for carbohydrates.

One or two drops of alcoholic solution of $\alpha$ -naphthol is added to

2

ml glucose solution.

1

ml of conc.

{H_2}S{O_4}

solution is added carefully along the sides of the test-tube.

The formation of a violet ring at the junction of two liquids confirms the presence of a carbohydrare or sugar.

Q126

Stability of

\alpha

-Helix structure of proteins depends upon

A dipolar interaction

B H-bonding interaction

C van der Waals forces

\pi

-stacking interaction

Correct Answer

Option B

Solution

Mostly $\mathrm{H}$ -bonding is responsible for the stability of $\alpha$ -helix form.

Q127

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) :

\alpha

-halocarboxylic acid on reaction with dil.

\mathrm{NH_3}

gives good yield of

\alpha

-amino carboxylic acid whereas the yield of amines is very low when prepared from alkyl halides. Reason (R) : Amino acids exist in zwitter ion form in aqueous medium. In the light of the above statements, choose the correct answer from the options given below :

A (A) is not correct but (R) is correct

B (A) is correct but (R) is not correct

C Both (A) and (R) are correct but (R) is not the correct explanation of (A)

D Both (A) and (R) are correct and (R) is the correct explanation of (A)

Correct Answer

Option D

Solution

The reaction of $\alpha$ -halocarboxylic acid with dilute ammonia is known as the haloform reaction.

In this reaction, the halogen atom of $\alpha$ -halocarboxylic acid is replaced by an amino group to form $\alpha$ -amino carboxylic acid.

The yield of $\alpha$ -amino carboxylic acid is good because the amino group is a better nucleophile than the halogen atom, and it attacks the carbonyl carbon of the carboxylic acid to form an intermediate, which is then hydrolyzed to form the product.

On the other hand, when alkyl halides are reacted with ammonia, the yield of amines is very low because alkyl halides are less reactive than $\alpha$ -halocarboxylic acids.

The reason (R) is also true.

Amino acids exist in the zwitterion form in an aqueous medium.

In this form, the amino group has a positive charge, and the carboxyl group has a negative charge.

The zwitter ion form is stabilized by the interaction between the opposite charges, which is known as an electrostatic interaction.

This interaction makes the zwitterion form more stable than the neutral form.

Q128

RNA is different from DNA because RNA contains

A ribose sugar and thymine

B ribose sugar and uracil

C deoxyribose sugar and thymine

D deoxyribose sugar and uracil

Correct Answer

Option B

Solution

The correct answer is Option B: RNA contains ribose sugar and uracil.

Here's a brief explanation: DNA contains deoxyribose sugar, while RNA contains ribose sugar.

DNA uses thymine as one of its bases, but RNA uses uracil instead.

This difference is one of the key distinguishing features between RNA and DNA.

Q129

A non-reducing sugar "A" hydrolyses to give two reducing mono saccharides. Sugar A is

A Fructose

B Galactose

C Glucose

D Sucrose

Correct Answer

Option D

Solution

Sucrose

\overset{{Hydrolyses}}\longrightarrow

glucose + fructose Glucose and fructose both are monosaccharides. Sucrose is non-reducing sugar.

Q130

Number of stereo centers present in linear and cyclic structures of glucose are respectively :

A 4 & 4

B 4 & 5

C 5 & 4

D 5 & 5

Correct Answer

Option B

Solution

In this linear structure 4 chiral carbons present. In this cyclic structure 5 chiral carbons present.

Ready for a full NEET mock test? Timed · full syllabus · instant results

Take a Mock Test →