Biomolecules MCQ Questions & Answers in Organic Chemistry | Chemistry
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71.
The central dogma of molecular genetics states that the genetic information flows from
A
amino acids → proteins → $$DNA$$
B
$$DNA$$ → carbohydrates → proteins
C
$$DNA$$ → $$RNA$$ → proteins
D
$$DNA$$ → $$RNA$$ → carbohydrates
Answer :
$$DNA$$ → $$RNA$$ → proteins
The central dogma of molecular genetics states that
\[DNA\xrightarrow{\text{Transcription}}RNA\xrightarrow{\text{Translation}}\text{Protein}\]
Thus, option (C) is correct.
72.
Which of the following statement is not correct ?
A
Amylopectin is a branched polymer of $$\alpha $$ - glucose.
B
Cellulose is a linear polymer of $$\beta $$ - glucose
C
Glycogen is the food reserve of plants
D
All proteins are polymers of $$\alpha $$ - amino acids.
Answer :
Glycogen is the food reserve of plants
Glycogen is called animal starch and is found in all animal cells. It constitutes the reserve
food material.
74.
The correct statement regarding $$RNA$$ and $$DNA,$$ respectively is
A
The sugar component in $$RNA$$ is ribose and the sugar component in $$DNA$$ is $$2'$$ - deoxyribose
B
The sugar component in $$RNA$$ is arabinose and the sugar component in $$DNA$$ is ribose
C
The sugar component in $$RNA$$ is $$2'$$ - deoxyribose and the sugar component in $$DNA$$ is arabinose
D
The sugar component in $$RNA$$ is arabinose and the sugar component in $$DNA$$ is $$2'$$ - deoxyribose
Answer :
The sugar component in $$RNA$$ is ribose and the sugar component in $$DNA$$ is $$2'$$ - deoxyribose
In $$DNA,$$ two helically twisted strands connected together by steps. Each strand consists of alternating molecules of deoxyribose at $$2'$$ - position and phosphate groups.
On the other hand, in $$RNA,$$ the pentose sugar has an identical structure with deoxyribose sugar except that there is an $$ - OH$$ group instead of $$ - H$$ on carbon atom $$2'.$$
Hence, it is only called ribose.
75.
Which of the following does not exihibit the phenomena of mutarotation?
A
$$\left( + \right)$$ Sucrose
B
$$\left( + \right)$$ Lactose
C
$$\left( + \right)$$ Maltose
D
$$\left( - \right)$$ Fructose
Answer :
$$\left( + \right)$$ Sucrose
Key Idea Reducing sugars that exist in hemiacetal and hemiketal forms, exhibit the phenomenon of mutarotation in aqueous solution. During mutarotation, the ring open upto give the open chain form which then reclose either in the inverted position or in the original position giving an equilibrium mixture of two anomers with a small amount of open chain form. Thus, all reducing monosaccharides and disaccharides undergo mutarotation in aqueous solution.
Among the given carbohydrates, only sucrose is a non-reducing sugar as in it the hemiacetal and hemiketal groups of glucose and fructose are linked together through $$O$$ - atom and thus, not free. Due to the absence of free hemiacetal or hemiketal group, sucrose does not exhibit mutarotation.
76.
Which of the following could act as a propellant for rockets?
A
Liquid oxygen + liquid argon
B
Liquid hydrogen + liquid oxygen
C
Liquid nitrogen + liquid oxygen
D
Liquid hydrogen + liquid nitrogen
Answer :
Liquid hydrogen + liquid oxygen
Liquid hydrogen and liquid oxygen are used as excellent fuel for rockets. $${H_2}\left( \ell \right)$$ has low mass and high enthalpy of combustion whereas oxygen is a strong supporter of combustion.
77.
The $$\alpha {\text{ - }}$$ and $$\beta {\text{ - }}$$ forms of glucose are
A
isomers of $$D(+)$$ glucose and $$L(-)$$ glucose respectively
B
diastereomers of glucose
C
anomers of glucose
D
isomers which differ in the configuration of $$C{\text{ - 2}}$$
Answer :
anomers of glucose
No explanation is given for this question. Let's discuss the answer together.
78.
In aqueous solutions, amino acids mostly exist as
In aqueous solutions, amino acids mostly exist as zwitter ion or dipolar ion.
\[\underset{\text{zwitter ion}}{\mathop{\overset{+}{\mathop{N}}\,{{H}_{3}}\overset{\begin{smallmatrix}
R\,\,\, \\
|\,\,\,
\end{smallmatrix}}{\mathop{-CH-}}\,CO{{O}^{-}}}}\,\]
79.
Which of the following statements is true for proteins?
A
They act as antibodies.
B
They act as hormones.
C
They catalyse the biochemical reactions.
D
All of these.
Answer :
All of these.
Antibodies, hormones, enzymes (biocatalyst) all are proteins.
80.
The $$\alpha {\text{ - }}D{\text{ - }}$$ glucose and $$\beta {\text{ - }}D{\text{ - }}$$ glucose differ from
each other due to difference in carbon atom with respect to its
A
conformation
B
configuration
C
number of $$OH$$ - groups
D
size of hemiacetal ring
Answer :
configuration
The isomer having the hydroxyl group $$\left( { - OH} \right)$$ on the right is called $$\alpha {\text{ - }}D{\text{ - }}$$ glucose and one having the hydroxyl group $$\left( { - OH} \right)$$ on the left is called $$\beta {\text{ - }}D{\text{ - }}$$ glucose. Such pairs of optical isomers which differ in the configuration only around $${C_1}$$ atom are called amomers. Thus $$\alpha {\text{ - }}D{\text{ - }}$$ glucose and $$\beta {\text{ - }}D{\text{ - }}$$ glucose are anomers.