Text Book Back Questions and Answers - Chapter 14 - Biomolecules - 12th Chemistry Guide Samacheer Kalvi Solutions

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Biomolecules
Textual Evaluation Solved
Multiple Choice Questions
Question 1.
Which one of the following rotates the plane polarized light towards left?
(a) $\mathrm{D}(+)$ Glucose
(b) $\mathrm{L}(+)$ Glucose
(c) $\mathrm{D}(-)$ Fructose
(d) $\mathrm{D}(+)$ Galactose
Answer:
(c) D(-) Fructose
Question 2.
The correct corresponding order of names of four aldoses with configuration given below Respectively is
(a) L-Erythrose, L-Threose, L - Erythrose, D - Threose
(b) D - Threose, D - Erythrose, L - Thrcose, L - Erythrose
(c) L-Etythrose, L-Threose, D - Erythrose, D - Threose
(d) D - Erythrose, D - Threose, L-Erythrose, L-Threose
Answer:
(d) D - Erythrose, D - Threose, L-Erythrose, L-Threose
Question 3.
Which one given below is a non-reducing sugar?
(a) Glucose
(b) Sucrose
(c) maltose
(d) Lactose
Answer:
(b) Sucrose
Question 4.
Glucose(HCN) Product (hydrolysis) Product (HI + Heat) A, the compound A is
(a) Heptanoic acid
(b) 2 -lodohexane
(c) Heptane
(d) Heptanol
Answer:
(a) Heptanoic acid

Question 5.
Assertion: A solution of sucrose in water is dextrorotatory. But on hydrolysis in the presence of little hydrochloric acid, it becomes levorotatory.
Reason: Sucrose hydrolysis gives unequal amounts of glucose and fructose. As a result of this change in sign of rotation is observed.
(a) If both accretion and reason are true and reason is the correct explanation of assertion
(b) If both assertion and reason are true but reason is not the correct explanation of assertion
(c) If assertion is true but reason is false
(d) if both assertion and reason are false
Answer:
(a) If both accretion and reason are true and reason is the correct explanation of assertion
Qustion 6.
The central dogma of molecular genetics states that the genetic information flows from
(a) Amino acids Protein DNA
(b) DNA Carbohydrates Proteins
(c) DNA RNA Prnteins
(d) DNA RNA Carbohydrates
Answer:
(c) DNA RNA Proteins
Question 7.
In a protein, various amino acids liked together by
(a) Peptide bond
(b) Dative bond
(c) $\alpha$-Glycosidic bond
(d) $\beta$-Glycosidic bond
Answer:
(a) Peptide bond
Question 8.
Among the following the achiral amino acid is
(a) 2 - ethylalanine
(b) 2 - methyiglycine
(c) 2 -hydroxymethyiscrine
(d) Tryptophan
Answer:
(c) 2-hydroxymethylserine
Question 9.
The correct statement regarding RNA and DNA respectively is
(a) the sugar component in RNA is an arabinose and the sugar component in DNA is ribose
(b) the sugar component in RNA is 2' - deoxyribose and the sugar component in DNA is arabinose

(c) the sugar component in RNA is an arabinose and the sugar component in DNA is 2' - deoxyribose
(d) the sugar component in RNA is ribose and the sugar component in DNA is 2'-deoxyribose
Answer:
(d) the sugar component in RNA is ribose and the sugar component in DNA is 2'-deoxyribose
Question 10.
In aqueous solution of amino acids mostly exists in
(a) $\mathrm{NH}_2-\mathrm{CH}(\mathrm{R})-\mathrm{COOH}$
(b) $\mathrm{NH}_2-\mathrm{CH}(\mathrm{R})-\mathrm{COO}$
(c) $\mathrm{H}_3 \mathrm{~N}-\mathrm{CH}(\mathrm{R})-\mathrm{COOH}$
(d) $\mathrm{H}_3 \mathrm{~N}^{+}-\mathrm{CH}(\mathrm{R})-\mathrm{COO}^{-}$
Answer:
(d) $\mathrm{H}_3 \mathrm{~N}^{+}-\mathrm{CH}(\mathrm{R})-\mathrm{COO}^{-}$
Question 11.
Which one of the following is not produced by body?
(a) DNA
(b) Enzymes
(c) Hormones
(d) Vitamins
Answer:
(d) Vitamins
Question 12.
The number of $\mathrm{sp}^2$ and $\mathrm{sp}^3$ hybridised carbon in fructose are respectively
(a) 1 and 4
(b) 4 and 2
(c) 5 and 1
(d) 1 and 5
Answer:
(d) 1 and 5
Question 13.
Vitamin $B_2$ is also known as
(a) Riboflavin
(b) Thiamine
(c) Nicotinamide
(d) Pyridoxine
Answer:
(a) Riboflavin

Question 14.
The pyrimidine bases present in DNA are
(a) Cytosine and Adenine
(b) Cytosine and Guanine
(c) Cytosine and Thiamine
(d) Cytosine and Uracil
Answer:
(c) Cytosine and Thiamine
Question 15.
Among the following $\mathrm{L}$ - serine is
(a) $\mathrm{H}_2 \mathrm{~N}-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{COOH}$

Answer:

Question 16.
The secondary structure of a protein refers to
(a) fixed configuration of the polypeptide backbone
(b) hydrophobic interaction
(c) sequence of a-amino acids
(d) $\alpha$-helical backbone
Answer:
(d) $\alpha$-helical backbone
Question 17.
Which of the following vitamins is water soluble?
(a) Vitamin $E$
(b) Vitamin $\mathrm{K}$
(c) Vitamin A
(d) Vitamin B
Answer:
(b) Vitamin $\mathrm{K}$
Question 18 .
Complete hydrolysis of cellulose gives
(a) $\mathrm{L}-$ Glucose
(b) D-Fructose
(c) D-Ribose
(d) D-Glucose
Answer:
(d) D-Glucose
Question 19.
Which of the following statement is correct?
(a) Ovalbumin is a simple food reserve in egg-white
(b) Blood proteins thrombin and fibrinogen are involved in blood clotting
(c) Denaturation makes protein more active
(d) Insulin maintains the sugar level of in the human body
Answer:
(c) Denaturation makes protein more active

Question 20 .
Glucose is an aldose. Which one of the following reactions is not expected with glucose?
(a) It does not form oxime
(b) It does not react with Grignard reagent
(c) It does not form osazones
(d) It does not reduce tollens reagent
Answer:
(b) It does not react with Grignard reagent
Question 21.
If one strand of the DNA has the sequence 'ATGCTTGA', then the sequence of complementary strand would be
(a) TACGAACT
(b) TCCGAACT
(c) TACGTACT
(d) TACGRAGT
Answer:
(a) TACGAACT
Question 22.
Insulin, a hormone chemically is
(a) Fat
(b) Steroid
(c) Protein
(d) Carbohydrates
Answer:
(c) Protein
Question 23.
$a-D(+)$ Glucose and $B-D(+)$ glucose are
(a) Epimers
(b) Anomers
(c) Enantiomers
(d) Conformational isomers
Answer:
(b) Anomers
Question 24.
Which of the following are epimers?

(a) $\mathrm{D}(+)-$ Glucose and $\mathrm{D}(+)-$ Galactose
(b) $\mathrm{D}(+)$ - Glucose and $\mathrm{D}(+)$ - Mannose
(c) Neither (a) nor (b)
(d) Both (a) and (b)
Answer:
(d) Both (a) and (b)
Question 25.
Which of the following amino acids are achiral?
(a) Alanine
(b) Leucine
(c) Proline
(d) Glycine
Answer:
(a) Alanine
II. Answer the following questions.
Question 1.
What type of linkages hold together monomers of DNA?
Answer:
1. Phospho diester linkages hold together monomers of DNA
2. Phosphoric acid forms phospho diester bond between neucleotides
3. The sugar - phosphate linkage forms the backbone of each strand of DNA.

Question 2.
Give the differences between primary and secondary structure of proteins.
Answer:
Primary structure of proteins
1. Linear sequence of amino acids
2. Composed of peptide bonds formed between amino acids.
3. Formed during translation.
4. Involved in post - translational modifications.
Secondary structure of proteins
1. Folding of the peptide chain into an a-helix and 13-sheet.
2. Encompasses hydrogen bonds
3. Forms collagen, elastin action, myosin, and keratin - like fibres.
4. Involved in forming structures such as cartilages, ligaments, skins etc.
Question 3.
Name the Vitamins whose deficiency cause
1. rickets
2. scurvy
Answer:
1. Vitamin - D deficiency causes rickets disease.
2. Vitamin $-\mathrm{C}$ deficiency causes scurvy disease.
Question 4.
Write the Zwitter ion structure of alanine.

Answer:
Zwitter ion structure of alanine

Question 5 .
Give any three difference between DNA and RNA.
Answer:
DNA
1. It is mainly present in nucleus, mitochondria and chloroplast .
2. It contains deoxyribose sugar
3. Base pair $\mathrm{A}=\mathrm{T} . \mathrm{G}=\mathrm{C}$
4. Double stranded molecules
5. Its life time is high
6. it is stable and not hydrolysed easily by alkalis
7. It can replicate itself
RNA
1. It is mainly present in cytoplasm, nucleolus and ribosomes
2. It contains ribose sugar
3. Base pair $\mathrm{A}=\mathrm{U} . \mathrm{C}=\mathrm{G}$
4. Single stranded molecules
5. It is Short lived
6. It is unstable and hydrolyzed easily by alkalis
7. It cannot replicate itself. It is formed from DNA.
Question 6.
Write a short note on peptide bond.
Answer:
1. The amino acids are linked covalently by peptide bonds.
2. The carbonyl group of the first amino acid react with the amino group of the second amino acid to give an amide linkage (- CONH) between these aminoacids. This amide linkage is called peptide bond.

3. The resulting compound is called a dipeptide. Because, two amino acids are inovived for getting one peptide bond.
4. If large number of amino acids combined through peptide bond, the resulting giant molecule is called a protein.
5. The amino end of the peptide is known as N-terminal, while the carboxy end is called $\mathrm{C}-$ terminal.
Question 7.
Give two difference between Hormones and vitamins.
Answer:
hormones
1. Hormones are produced in the endocrine or ductless glands.
2. Hormones are not stored in the body. These are produced as and when required.
3. They are effective in low concentration. Their excess or deficiency may cause hormonal disorders.
4. Hormones influence the genes to produce specific enzymes required during metabolism.
5. Example: Insulin
Vitamins
1. Vitamins (except Vitarnin - D) are not produced in the body. Vitamin must be supplied in the diet.
2. Vitamins are stored in the body upto certain extent.
3. They are needed in small quantity. Excess vitamins are excreted. Their deficiency causes
4. malfunctioning called deficiency diseases or avitaminosis.
5. They act as co-enzymes and help enzymes to perform their function.
6. Example: Vitamin A, B, C, D, E and K
Question 8 .
Write a note on den atu ration of proteins.
Answer:
Denaturation of proteins.
1. In general, protein has a unique three - dimensional structure formed by interactions such as disuiphide bond, hydrogen bond, hydrophobic and electrostatic interactions.
2. These interactions can be disturbed when the protein is exposed to a higher temperature in certain chemicals such urea, alternation of $\mathrm{pH}$, ionic strength etc. It leads to the loss of the three - dimensional structure.
3. The process of a protein losing its higher order structure without losing the primary structure, It is called denaturation of protein. When a protein denatures, its biological function is also lost.
4. Since the primary structure is intact, this process can be reversed in certain proteins. This can happen spontaneously upon restoring the original conditions or with the help of special enzymes called cheperons.

5. Example: Coagulation of egg white by action of heat.
Question 9.
What are reducing and non - reducing sugars?
Answer:
1. Reducing sugars:
Those carbonhydrates which contain free aldehyde or ketonic group and reduces Fehling's solution and Tollen's reagent are called reducing sugars. All monosacehaides whether aldose or ketone are reducing sugars.
2. Non - reducing sugars:
Cabohydrates which do not reduce Tollen's reagent and Fehling's solution are called non - reducing sugars. Example Sucrose. They do not have free aldehyde group.
Question 10.
Why carbohydrates are generally optically active?
Answer:
Carbohydrates are generally optically active because they have one or more chiral carbon atoms in their molecules. For example, Glucose has four chiral carbons and therefore it is optically active.

Question 11.
Classify the following into monosaccharides, oligosaccharides and polysaccharldes.
1. Starch
2. fructose
3. sucrose
4. lactose
5. maltose
Answer:
1. Starch-Polysaccharides
2. Furctose - Mono saccharides
3. Sucrose-Oligo saccharide
4. Lactose - Oligo saccharide
5. Maltose-Oligo saccharide
Surcose, Lactose and Maltose are typical disaccharides
Question 12.
How are vitamins classified?
Answer:
Vitamins are classified into two groups based on their solubility in water and in fat. They are,
1. Water - soluble vitamins
2. Oil or fat - soluble vitamins
Water - soluble vitamins - Vitamins which dissolve in water are called water soluble vitamins. Examples Vitamins of B group and Vitamin C Oil or fat - soluble vitamins: Vitamins which dissolve in oils or fat are called oil or fat - soluble vitamins. Examples - Vitamin A, D, E and $\mathrm{K}$
Question 13.
What are hormones? Give examples.
Answer:
Hormone is an organic substance that is sëcreted by one tissue into the blood stream and induces a physiological response in other tissues. It is an inter cellular signaling molecule. Virtually every process is a complex organism is regulated by one or more hormones. Example, insulin, epinephrine, estrogen, androgen etc.
Question 14 .
Write the structure of all possible dipeptides which can be obtained from glycine and atanine.

Answer:

Therefore two dipeptides structures are possible from glycine and alanine. They are
1. glycyl alanine and
2. Alanyl glycine
Question 15.
Define enzymes.
Answer:
There are many biochemical reactions that occur in our living cells. Digestion of food and harvesting the energy from them, and synthesis of necessary molecules required for various - cellular functions are examples for such reactions. All these reactions are catalysed by special proteins called enzymes.
(or)
Enzymes are bio catalysts produced by the living cells which catalyse many biochemical reactions in animal and plant bodies. They are more specific in their action.
Question 16.
Write the structure of $-\mathrm{D}(+)$ glucopyranose.
Answer:

Question 17.
What are different types of RNA which are found in cell?
Answer:
RNA molecules are classified according to their structure and function into three major types.
1. Ribosomal RNA (r-RNA)
2. Messenger RNA (m - RNA)
3. Transfer RNA ( $\mathrm{t}-\mathrm{RNA})$
r-RNA:
rRNA is mainly found in cytoplasm and in ribosomes, which contain $60 \%$ RNA and $40 \%$ protein.
Ribosomes are the sites at which protein synthesis takes place.
$\mathrm{t}-\mathrm{RNA}$ :
tRNA molecules have lowest molecular weight of all nucleic acids. They consist of $73-94$ nucleotides in a single chain. The function of tRNA is to carry amino acids to the sites of protein synthesis on ribosomes.
$\mathrm{m}-\mathrm{RNA}$ :
mRNA is present in small quantity and very short lived. They are single stranded, and their synthesis takes place on DNA. The synthesis of mRNA from DNA strand is called transcription. mRNA carries genetic information from DNA to the ribosomes for protein synthesis.
Question 18 .
Write a note on formation of - helix.
Answer:
1. In the $\alpha$ - helix sub - structure, the aminoacids are arranged in a right handed helical (spiral) structure and are stabilised by the hydrogen bond between the carbonyl oxygen one aminoacid (n ${ }^{\text {th }}$ residue) with amino hydrogen of the fifth residue $\left(n+4^{\text {th }}\right.$ residue)
2. The side chains of the residues protrude outside of the helix. Each turn of an $\alpha-$ helix contains about 3.6 residues and is about $5.4 \mathrm{~A}$ long.
3. The amino acid proline produces a line in the helical structure and often called as a helical breaker due to its rigid cyclic structure.
4. Many fibrous proteins such as ct-Keratin in hair, nails, wool, skin and myosin in muscles have $\alpha-$ helix structure. Stretching property of human hair is due to the helical structure of $\alpha$-keratin in hair.

5. Structure of a-helix.

Question 19.
What are the functions of lipids in living organism?
Answer:
1. Lipids are the integral component of cell membrane. They are necessary of structural integrity of the cell.
2. The main function of triglycerides in animals is as an energy reserve. They yield more energy than carbohydrates and proteins.
3. They act as protective coating in aquatic organisms.
4. Lipids of connective tissue give protection to internal organs.
5. Lipids help in the absorption and transport of fat soluble vitamins.
6. They are essential for activation of enzymes such as lipases.
7. Lipids act as emulsifier in fat metabolism.
Question 20
Is the following sugar, D-sugar or L-sugar?
Answer: