Biomolecules MCQ Questions & Answers in Organic Chemistry | Chemistry
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141.
Nucleic acids are the polymers of _________.
A
nucleosides
B
nucleotides
C
bases
D
sugars
Answer :
nucleotides
Nucleic acids are long chain polymers of nucleotides hence, are also called polynucleotides.
142.
Which of the following bases is not present in $$DNA?$$
A
Adenine
B
Thymine
C
Cytosine
D
Uracil
Answer :
Uracil
Uracil is not present in $$DNA.$$
143.
Which of the following is correct about $$H$$ - bonding in nucleotide?
A
$$A - T,\,G - C$$
B
$$A - G,\,T - C$$
C
$$G - T,\,A - C$$
D
$$A - A,\,T - T$$
Answer :
$$A - T,\,G - C$$
The structure of $$DNA$$ molecule is a double helical structure. In this structure double helix are made up of two right handed helical polynucleotide chains which are held together by $$H$$ - bonds. In these helixes the adenine $$(A)$$ base is linked with thymine $$(T)$$ by two $$H$$ - bonds and guanine $$(G)$$ is linked with cytocine $$(C)$$ by three $$H$$ - bonds as $$A = T,$$ and $$G \equiv C.$$
144.
Vitamin $${B_2},$$ a water soluble vitamin is also known as
A
ascorbic acid
B
riboflavin
C
thiamine
D
pyridoxine
Answer :
riboflavin
No explanation is given for this question. Let's discuss the answer together.
145.
Globular proteins are present in
A
blood
B
eggs
C
milk
D
all of these
Answer :
all of these
No explanation is given for this question. Let's discuss the answer together.
146.
Sucrose (cane sugar) is a disaccharide. One molecule of sucrose on hydrolysis gives __________.
A
2 molecules of glucose
B
2 molecules of glucose + 1 molecule of fructose
C
1 molecule of glucose + 1 molecule of fructose
D
2 molecules of fructose
Answer :
1 molecule of glucose + 1 molecule of fructose
147.
The pair of compounds in which both the compounds give positive test with Tollen’s reagent is
A
Glucose and Sucrose
B
Fructose and Sucrose
C
Acetophenone and Hexanal
D
Glucose and Fructose
Answer :
Glucose and Fructose
Glucose being an aldose responds to Tollen’s test while fructose, although a ketose, undergoes rearrangement in presence of basic medium ( provided by Tollen’s reagent ) to form glucose, which then responds to Tollen’s test.
148.
Which of the following is not true about amino acids?
A
They are constituents of all proteins.
B
Alanine having one amino and one carboxylic group.
C
Most naturally occurring amino acids have $$D$$ - configuration.
D
Glycine is the only naturally occurring amino acid which is optically inactive.
Answer :
Most naturally occurring amino acids have $$D$$ - configuration.
Most naturally occurring amino acids have $$L$$ - configuration.
149.
In osazone formation, glucose reacts with three molecules of phenylhydrazine. Which statement is true regarding this ?
A
All the three molecules react in similar fashion
B
Two molecules react in similar manner, while the third reacts in different way
C
All the three molecules react in different ways
D
None of the above is true
Answer :
Two molecules react in similar manner, while the third reacts in different way
First molecule of phenylhydrazine unedrgoes nucleophilic addition on carbonyl ( $$-CHO$$ in glucose and $$ > CO$$ in fructose ) group. Second molecule of the reagent oxidizes $$ - CHOH - $$ at position 2 ( in aldoses ) or $$ - C{H_2}OH$$ at position 1 ( in ketoses ) to form $$ - CHO$$ or $$ > C = O$$ respectively. The third molecule again undergoes nucleophilic addition on the newly developed carbonyl group to form osazone.
150.
Which of the following pairs represents anomers?
A
B
C
D
Answer :
The two cyclic hemiacetal forms of monosaccharide which differ only in the configuration of the hydroxyl group at $$C{\text{ - }}1$$ are anomers.