CUET Chemistry Set-7: Biomolecules & Polymers
Question 1
The pyranose structure of glucose is a six-membered heterocyclic ring containing
(1) five carbons and one oxygen
(2) four carbons and two oxygens
(3) six carbons and no oxygen
(4) three carbons and three oxygens
Show Answer
Answer: (1)
Solution: Pyranose is a six-membered ring with five carbons and one oxygen (analogous to pyran).
Question 2
Which of the following is not a monosaccharide?
(1) Glucose
(2) Fructose
(3) Ribose
(4) Sucrose
Show Answer
Answer: (4)
Solution: Sucrose is a disaccharide (glucose + fructose), not a monosaccharide.
Question 3
The linkage that joins two amino acids in a protein is
(1) glycosidic
(2) peptide
(3) ester
(4) phosphodiester
Show Answer
Answer: (2)
Solution: Peptide bond (–CO–NH–) links amino acids.
Question 4
The secondary structure of proteins is mainly stabilized by
(1) ionic bonds
(2) hydrogen bonds
(3) disulphide bridges
(4) hydrophobic interactions
Show Answer
Answer: (2)
Solution: $\alpha$-helix & $\beta$-pleated sheet are H-bond stabilized.
Question 5
Which base is present in RNA but not in DNA?
(1) Cytosine
(2) Thymine
(3) Uracil
(4) Guanine
Show Answer
Answer: (3)
Solution: Uracil replaces thymine in RNA.
Question 6
The number of chiral carbons in $\beta$-D-glucopyranose is
(1) 3
(2) 4
(3) 5
(4) 6
Show Answer
Answer: (3)
Solution: C-2, 3, 4, 5 & the anomeric C-1 are chiral → 5 chiral centres.
Question 7
Hydrolysis of lactose yields
(1) glucose + galactose
(2) glucose + fructose
(3) two glucose units
(4) galactose + fructose
Show Answer
Answer: (1)
Solution: Lactose = Gal-$\beta$(1→4)-Glc.
Question 8
Which polymer is an example of a polyamide?
(1) Terylene
(2) Nylon-6,6
(3) PVC
(4) Bakelite
Show Answer
Answer: (2)
Solution: Nylon-6,6 contains repeating amide linkages.
Question 9
The monomer of natural rubber is
(1) chloroprene
(2) isoprene
(3) butadiene
(4) propylene
Show Answer
Answer: (2)
Solution: cis-1,4-Polyisoprene.
Question 10
Which of the following is a biodegradable polymer?
(1) PHBV
(2) Polystyrene
(3) Teflon
(4) PVC
Show Answer
Answer: (1)
Solution: PHBV (poly-$\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate) is biodegradable.
Question 11
The anomeric carbon in a cyclic monosaccharide is the carbon derived from
(1) the carbonyl carbon of the open-chain form
(2) the highest numbered chiral carbon
(3) the carbon involved in glycosidic linkage only
(4) the methyl carbon
Show Answer
Answer: (1)
Solution: Carbonyl C (C-1 in aldoses) becomes anomeric in ring form.
Question 12
Which reagent is used for the estimation of reducing sugars?
(1) Fehling’s solution
(2) Molisch’s reagent
(3) Biuret reagent
(4) Ninhydrin
Show Answer
Answer: (1)
Solution: Fehling’s gives red ppt. with reducing sugars.
Question 13
The helical structure of DNA is stabilized primarily by
(1) covalent bonds between bases
(2) hydrogen bonds between complementary bases
(3) ionic bonds between phosphate and base
(4) disulphide bonds
Show Answer
Answer: (2)
Solution: A–T (2 H-bonds) & G–C (3 H-bonds) pairing.
Question 14
Which of the following is a non-reducing sugar?
(1) Maltose
(2) Lactose
(3) Trehalose
(4) Cellobiose
Show Answer
Answer: (3)
Solution: Trehalose (Glc$\alpha$(1→1)$\alpha$Glc) has no free anomeric OH.
Question 15
The polymer formed by step-growth mechanism among the following is
(1) polyethylene
(2) polypropylene
(3) nylon-6
(4) polystyrene
Show Answer
Answer: (3)
Solution: Nylon-6 is condensation (step-growth); others are chain (addition).
Question 16
In amylopectin, branching occurs through which linkage?
(1) $\alpha$-1,4
(2) $\alpha$-1,6
(3) $\beta$-1,4
(4) $\beta$-1,6
Show Answer
Answer: (2)
Solution: Branch points are $\alpha$(1→6) glycosidic.
Question 17
The isoelectric point (pI) of an amino acid is the pH at which it
(1) exists as a cation
(2) exists as an anion
(3) has net zero charge
(4) precipitates as metal complex
Show Answer
Answer: (3)
Solution: At pI, zwitterion has equal + and – charges → net zero.
Question 18
Which polymer contains urea as one of its monomer units?
(1) Urea-formaldehyde resin
(2) Melamine-formaldehyde
(3) Bakelite
(4) Glyptal
Show Answer
Answer: (1)
Solution: Urea + formaldehyde → UF resin.
Question 19
The repeating unit of natural cellulose is
(1) glucose $\alpha$-1,4
(2) glucose $\beta$-1,4
(3) galactose $\beta$-1,4
(4) mannose $\alpha$-1,6
Show Answer
Answer: (2)
Solution: Cellulose = $\beta$-D-Glc(1→4) repeat.
Question 20
Which of the following is a chain-growth polymer?
(1) Polyester
(2) Polyamide
(3) Polyurethane
(4) Polyacrylonitrile
Show Answer
Answer: (4)
Solution: Polyacrylonitrile is addition (chain) polymer of acrylonitrile.
Question 21
Denaturation of proteins leads to loss of
(1) primary structure
(2) biological activity
(3) peptide bonds
(4) amino acid composition
Show Answer
Answer: (2)
Solution: Secondary & tertiary structures disrupted → activity lost; primary intact.
Question 22
The monomer unit of PVC is
(1) vinyl chloride
(2) ethylene
(3) tetrafluoroethylene
(4) acrylonitrile
Show Answer
Answer: (1)
Solution: CH$_2$=CHCl.
Question 23
Which of the following is a homopolymer?
(1) Nylon-6,6
(2) Bakelite
(3) Teflon
(4) PHBV
Show Answer
Answer: (3)
Solution: Teflon is homopolymer of tetrafluoroethylene; others are copolymers.
Question 24
The number of hydrogen bonds between adenine and thymine in a DNA double helix is
(1) 1
(2) 2
(3) 3
(4) 4
Show Answer
Answer: (2)
Solution: A–T pair forms two H-bonds.
Question 25
Which of the following statements about glycogen is correct?
(1) It is a linear polymer of $\beta$-glucose
(2) It contains only $\alpha$-1,4 linkages
(3) It is more branched than amylopectin
(4) It is insoluble in water
Show Answer
Answer: (3)
Solution: Glycogen is highly branched (every 8–10 residues) via $\alpha$-1,6, more than amylopectin.
BETA
