NEET Chemistry Biomolecules Questions Solved


Phspholipids are esters of glycerol with

(a) one carboxylic acid residue and two phosphate groups

(b) three phosphate groups

(c) three carboxylic acid residues

(d) two carboxylic acid residues and one phosphate groups

(d) Phospholipids are esters of glycerol with two carboxylic acid residue and one phosphate group. Hence, phospholipids may be regarded as derivative of glycerol in which two hydroxyl groups are esterified with fatty acid, while third is esterified with phosphoric acid.

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Which one of the following gives positive Fehling's solution test ?

(a) Sucrose

(b) Glucose

(c) Fats

(d) Protein

(b) Glucose reduces Fehling solution to give red ppt. of Cu2O.

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Which of the following is the sweetest sugar?

(a) Sucrose

(b) Glucose

(c) Fructose

(d) Maltose

(c) Fructose is the sweetest sugar and highly soluble in water and slightly soluble in alcohol and insoluble in ether fructose in laevorotatory hence, called laevulose.

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Which one of the following sets of monosaccharides forms sucrose ?

(a) a-D-galactopyranose and a-D-glucopyranose

(b) a-D-glucopyranose and b-D-fructofuranose

(c) b-D-glucopyranose and a-D-fructofuranose

(d) b-D-glucopyranose and b-D-fructofuranose

(b) Sucrose is composed of a-D-glucopyranose and a b-D-fructofuranose units which are joined by a,b-glycosidic linkage between C-1 of the glucose unit and C-2 of the fructose unit

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a-D-(+)-glucose and b-D-(+)-glucose are

(a) anomers

(b) epimers

(c) enantiomers

(d) geometrical isomers

(a) Those diastereomers which differ only in configuration at C-1 are known as anomers

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The couplings between base units of DNA is through

(a) hydrogen bonding

(b) electrostatic bonding

(c) covalent bonding

(d) van der waal's forces

(a) In DNA the two strands are held together by hydrogen bonds. For example guanine is bonded to cytosine and adenine to thymine by hydrogen bonding.

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The segment of DNA which acts as the instrumental manual for the synthesis of the protein is 

(a) nucleotide

(b) ribose

(c) gene

(d) nucleoside

(c) The segment of DNA which acts as the instrumental manual for the synthesis of protein is gene. Every protein in a cell has a corresponding gene

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Which of the following structures represents the peptide chain ?

(c) The peptide linkage (-NH-CO-) is formed by the condensation of amino acids molecules

Hence, following structure represents the peptide chain

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Which of the following does not exihibit the phenomena of mutarotation?

(a) (+) Sucrose

(b) (+) Lactose

(c) (+) Maltose

(d) (-) Fructose

(a) Reducing sugars that exist in hemiacetal and hemiketal forms, 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 equlibrium 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 mutation.

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RNA and DNA are chiral molecules, their chirality is due to

(a) L-sugar component

(b) chiral bases

(c) chiral phosphate ester units

(d) D-sugar-component

(d) RNA and DNA molecules have ribose and deoxyribose sugar respectively. Both are chiral, their chirality is due to D-ribose or deoxyribose sugar components.

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