21.
Three cyclic structures of monosaccharides are given below. Which of these are anomers?
A
I and II
B
II and III
C
I and III
D
III is anomer of I and II
Answer :
I and II
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No explanation is given for this question. Let's discuss the answer together.
22.
Natural glucose is termed $$D$$ - glucose because :
A
$$ - OH$$ on the second carbon is on the right side in Fischer projection
B
$$ - OH$$ on the sixth carbon is on the right side in Fischer projection.
C
$$ - OH$$ on the fifth carbon is on the right side in Fischer projection.
D
It is dextrorotatory.
Answer :
$$ - OH$$ on the fifth carbon is on the right side in Fischer projection.
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Fischer gave the prefix $$“D”$$ to compounds whose bottom chiral has its $$OH$$ to the right. So natural glucose is called $$D$$ - glucose or dextrose.
Structure of $$D$$ - Glucose :
23.
The conversion of maltose into glucose is possible by the enzyme
A
zymase
B
lactase
C
maltase
D
diastase
Answer :
maltase
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\[\text{Maltose}\xrightarrow[{{H}^{+}}]{\text{Maltase}}\text{Glucose + Glucose}\]
24.
Which of the following aldohexoses give the same osazone derivative?
A
I and IV
B
I and III
C
II and III
D
III and IV
Answer :
I and III
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Structure I and II have different configurations at centres $$C{\text{ - }}1$$ and $$C{\text{ - 2}}$$ and identical configuration at $$C{\text{ - 3,}}\,C{\text{ - 4}}$$ and $$C{\text{ - 5}}$$ hence, gives same osazone.
25.
Which of the following is not present in a nucleotide ?
A
Guanine
B
Cytosine
C
Adenine
D
Tyrosine
Answer :
Tyrosine
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Tyrosine is an $$\alpha $$ - amino acid, and neither a purine nor a pyrimidine base
26.
Which of the following is not a function of proteins?
A
Formation of hair, wool, skin and nails.
B
As a biological catalysts in the form of enzymes.
C
As food in the form of meat, eggs.
D
As energy provider for metabolism.
Answer :
As energy provider for metabolism.
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Proteins are building blocks of the body but they do not provide energy for metabolism.
27.
Vitamin $$D$$ is also known as
A
sunshine vitamin
B
ascorbic acid
C
growth vitamin
D
reproductive vitamin
Answer :
sunshine vitamin
28.
In fructose, the possible optical isomers are
A
12
B
8
C
16
D
4
Answer :
8
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Fructose has 3 chiral centres and hence number of optical isomers are $${2^3} = 8$$
29.
Biuret test is not given by
A
carbohydrates
B
polypeptides
C
urea
D
proteins
Answer :
carbohydrates
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Biuret test produces violet colour on addition of dilute $$CaS{O_4}$$ to alkaline solution of a compound containing peptide linkage.
30.
Which statement is incorrect about peptide bond ?
A
$$C–N$$ bond length in proteins is longer than usual $$C–N$$ bond length
B
Spectroscopic analysis shows planar structure of
bond
C
$$C–N$$ bond length in proteins is smaller than usual $$C–N$$ bond length
D
None of these
Answer :
$$C–N$$ bond length in proteins is smaller than usual $$C–N$$ bond length
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Due to resonance,
$$C – N$$ bond acquires some double bond character, hence shorter in length