NEET Practice Questions (MCQs) with Answers & Solutions

(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.

 Glucose reduces Fehling solution to give red ppt. of Cu₂O.

$\underset{Glu\cos e}{\underset{CHO}{\overset{CHO}{\underset{\left|}{\overset{\right|}{{\left(\mathrm{CHOH}\right)}_4}}}}}+\underset{Fehling solution}{2CuO}\to \underset{C{H}_{\mathit{2}}OH}{\overset{COOH}{\underset{\left|}{\overset{\right|}{{\left(\mathrm{CHOH}\right)}_4}}}}+\underset{\mathrm{Red} \mathrm{ppt}}{{\mathrm{Cu}}_2\mathrm{O}}$

 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.

(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.

(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

 Starch is hydrolysed with dilute acids or enzymes and break down to molecules of variable complexity and finally gives D-glucose.

$$\begin{gathered} {\left({\mathrm{C}}_6{\mathrm{H}}_{10}{\mathrm{O}}_5\right)}_n \stackrel{ }{\to }{\left({\mathrm{C}}_6{\mathrm{H}}_{10}{\mathrm{O}}_5\right)}_{n\text{'}} \stackrel{ }{\to }{\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\stackrel{ }{\to }{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6 \\ \mathrm{Starch} \mathrm{Diastase} \mathrm{Maltose} \mathrm{D}-\mathrm{glucose} \end{gathered}$$

(a) 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.

(c) In the process of digestion the proteins present in food material are hydrolysed to amino acid. In this process two enzymes pepsin and trypsin are involve as follows :

$\mathrm{Proteins} \underset{(\mathrm{Enzyme} \mathrm{A})}{\overset{\mathrm{Pepsin}}{\to }} \mathrm{Polypeptide} \underset{(\mathrm{Enzyme} \mathrm{B})}{\overset{\mathrm{Trypsin}}{\to }} \mathrm{Amino} \mathrm{acid}$

(b) The helical structure of protein is stabilised by hydrogen bonds between amide group of the same peptide chain. These bonds are formed by -NH- group of one unit and oxygen of carbonyl group of the third unit. It takes 3.6 amino acid to complete one turn of the helix to enable. Such H-bonding and a 13 membering is formed by H-bonding. This H-bonding responsible for holding helix in a position.