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(A)alpha -amino acids have high melting ...

(A)`alpha` -amino acids have high melting point and show unusually high solubility in polar solvents.
(R) The Zwitter ion behaves like a salt.

A

Both (A) and (R) are true and (R) is the correct explanation of (A)

B

Both (A) and (R) are true and (R) is not the correct explanation of (A)

C

(A) is true but (R) is false

D

Both (A) and (R) are false

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The correct Answer is:
A
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alpha - amino acids are high melting crystalline solids because of the zwitterion structure. They are moderately soluble in water. In acidic medium, alpha - amino acids exist as cations (I) and thus migrate towards cathode under the influence of an electric field. On the other hand, in alkaline medium, alpha - amino acids exist as anions (III) and thus migrate towards anode under the influence of an electric field. However, at some intermediate value of p^(H) , the concentration of the cationic form (I) and anionic form (III) will become equal and consequently the alpha - amino acid will exist primarily as the neutral dipolar ion (II). At this p^(H) , there would be no net migration of the amino acid in an electric field. This p^(H) at which there is no net migration of the amino acid under the influence of an applied electric field is called isoelectric point (pI). Each amino acid has a characteristic isoelectric point. The pH of an amino acid that does not have an ionisable side chain such as alanine isd average of pK_(a) values of the carboxyl group and the protonated amino group. H_(3)overset(+)(N)-overset("R")overset("|")("C")H-COOH overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr H_(3)overset(+)(N)-underset("Zwitterion (II)")(overset("R")overset("|")("C")H)-COO^(-)overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr underset((III))(overset(+)(N)-overset("R")overset("|")("C")H)-COO^(-) Further, the alpha - carbon of all the amino acids (except glycine) is chiral (asymmetric) and hence amino acids can exist in teo stereoisomeric forms i.e., D and L. However, all the nautrally occurring amino acids belong to the L - series. underset("L(-)Glyceraldehyde")(HO-overset("CHO ")overset("| ")underset(" "CH_(2)OH)underset("| ")("C ")-H)" " underset("L-Amino acid")(H_(2)N-overset("COOH")overset("| ")underset("R ")underset("| ")("C ")-H) In alanine, carboxyl group ionises at pK_(a1)=2.34 and ammonium ion at pK_(a2)=9.69 . The isoelectric point of the amino acid is at p^(H) .

alpha - amino acids are high melting crystalline solids because of the zwitterion structure. They are moderately soluble in water. In acidic medium, alpha - amino acids exist as cations (I) and thus migrate towards cathode under the influence of an electric field. On the other hand, in alkaline medium, alpha - amino acids exist as anions (III) and thus migrate towards anode under the influence of an electric field. However, at some intermediate value of p^(H) , the concentration of the cationic form (I) and anionic form (III) will become equal and consequently the alpha - amino acid will exist primarily as the neutral dipolar ion (II). At this p^(H) , there would be no net migration of the amino acid in an electric field. This p^(H) at which there is no net migration of the amino acid under the influence of an applied electric field is called isoelectric point (pI). Each amino acid has a characteristic isoelectric point. The pH of an amino acid that does not have an ionisable side chain such as alanine isd average of pK_(a) values of the carboxyl group and the protonated amino group. H_(3)overset(+)(N)-overset("R")overset("|")("C")H-COOH overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr H_(3)overset(+)(N)-underset("Zwitterion (II)")(overset("R")overset("|")("C")H)-COO^(-)overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr underset((III))(overset(+)(N)-overset("R")overset("|")("C")H)-COO^(-) Further, the alpha - carbon of all the amino acids (except glycine) is chiral (asymmetric) and hence amino acids can exist in teo stereoisomeric forms i.e., D and L. However, all the nautrally occurring amino acids belong to the L - series. underset("L(-)Glyceraldehyde")(HO-overset("CHO ")overset("| ")underset(" "CH_(2)OH)underset("| ")("C ")-H)" " underset("L-Amino acid")(H_(2)N-overset("COOH")overset("| ")underset("R ")underset("| ")("C ")-H) N - terminus of the peptide structure is on the

alpha - amino acids are high melting crystalline solids because of the zwitterion structure. They are moderately soluble in water. In acidic medium, alpha - amino acids exist as cations (I) and thus migrate towards cathode under the influence of an electric field. On the other hand, in alkaline medium, alpha - amino acids exist as anions (III) and thus migrate towards anode under the influence of an electric field. However, at some intermediate value of p^(H) , the concentration of the cationic form (I) and anionic form (III) will become equal and consequently the alpha - amino acid will exist primarily as the neutral dipolar ion (II). At this p^(H) , there would be no net migration of the amino acid in an electric field. This p^(H) at which there is no net migration of the amino acid under the influence of an applied electric field is called isoelectric point (pI). Each amino acid has a characteristic isoelectric point. The pH of an amino acid that does not have an ionisable side chain such as alanine isd average of pK_(a) values of the carboxyl group and the protonated amino group. H_(3)overset(+)(N)-overset("R")overset("|")("C")H-COOH overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr H_(3)overset(+)(N)-underset("Zwitterion (II)")(overset("R")overset("|")("C")H)-COO^(-)overset(" "OH^(-)" ")underset(" "H^(+)" ")hArr underset((III))(overset(+)(N)-overset("R")overset("|")("C")H)-COO^(-) Further, the alpha - carbon of all the amino acids (except glycine) is chiral (asymmetric) and hence amino acids can exist in teo stereoisomeric forms i.e., D and L. However, all the nautrally occurring amino acids belong to the L - series. underset("L(-)Glyceraldehyde")(HO-overset("CHO ")overset("| ")underset(" "CH_(2)OH)underset("| ")("C ")-H)" " underset("L-Amino acid")(H_(2)N-overset("COOH")overset("| ")underset("R ")underset("| ")("C ")-H) Which of structural formula of lysine (NH_(2)-overset("COOH")overset("| ")("C ")H-CH_(2)-CH_(2)-CH_(2)-CH_(2)NH_(2)) at pH 13 ?

Ionic bond is defined as the electrostatic force of attraction holding the oppositely charged ions. Ionic compounds are mostly crystalline solids having high melting and boiling points, electrical conductivity in molten state, solubility in water etc., Covalent bond is defined as the force which binds atoms of same or different elements by mutual sharing of electrons in a covalent bond. Covalent compounds are solids, liquids or gases. They are low melting and boiling point compounds. They are more soluble in non polar solvents. The amount of energy released when one mole of ionic solid fonned by close packing of gaseous ions is called

Ionic bond is defined as the electrostatic force of attraction holding the oppositely charged ions. Ionic compounds are mostly crystalline solids having high melting and boiling points, electrical conductivity in molten state, solubility in water etc., Covalent bond is defined as the force which binds atoms of same or different elements by mutual sharing of electrons in a covalent bond. Covalent compounds are solids, liquids or gases. They are low melting and boiling point compounds. They are more soluble in non polar solvents. The valence electrons not involved in fonnation of covalent bonds are called

Hydrogen bonding is said to be formed, -when sightly acidic hydrogen-atom attached to a strongly, electronegative fluorine, oxygen or nitrogen atom. is held with weak. electrostatic forces by the non-bonded pair of electrons of another atom. The co-ordination number of hydrogen in such cases is two. It acts as a bridge between two atoms, to one of which it is covalently bonded and to other attached through electrostatic forces, also called hydrogen bond. Though the hydrogen atoms in a methyl group are not polarised, if an electronegative group like chloro, carbonyl, nitro or cyano (in order to increase electronegativity) is attached to it, the C-H bond gets polarised due to the inductive effect and the hydrogen atom becomes slightly acidic resulting in the formation of weak hydrogen bonds. Though a weak bond the H-bond effects is large number of the physical properties of compounds some of which are - Boiling points of liquids - Solubility of polar compounds in polar solvents (containig H attached with strong electronegative atom) - Viscosity of liquids . Acidity Which of the following combinations can involve hydrogen bonding I) Mixture of KF and HF " " II) Mixture of CH_(3)COCH_(3) and CHCI_(3) III) Mixture of NH_(4) CI and H_(2)O" " IV) Mixture of CH_(3) and H_(2)O

AAKASH SERIES-BIOMOLECULES-OBJECTIVE EXERCISE-4 (ASSERTION (A) & REASON (R) TYPE QUESTIONS :)
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  2. (A) Rate of the hydrolysis of sucrose in the presence of acid is less ...

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  3. (A)alpha -amino acids have high melting point and show unusually high ...

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  4. (A) Proteins are step growth polymers of alpha- amino acids. (R) alph...

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  5. (A) The proteins are synthesised by various RNA molecules in the cell....

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  6. (A) Tertiary structure of proteins represents overall folding i.e. fur...

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  7. (A) Valine and Leucine are essential amino acids. (R) Both valine an...

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  8. (A) Leucine and isoleucine are structural isomers. (R) Isoleucine ha...

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  9. (A) Xerophthalmia is treated with vitamin - B6 (R) Xerophthalmia is...

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  10. (A) Insulin contains two peptide chains. (R) Insulin is an example o...

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  11. (A) Vitamin 'C' is ascorbic acid. (R) All acids are vitamins

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  12. (A) All hormone receptors are proteins, (R) All hormones are protein...

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  13. (A) Water soluble vitamins like ascorbic acid must be supplied regular...

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  14. (A) Vitamins are important in diet. (R) Deficiency of vitamins cause...

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  15. (A) Insulin is a steroidal harmone. (R) A steroid contains two five ...

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  16. (A) Vitamins are considered as essential food factors. (R) Most of th...

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  17. (A) Vitamins are to be supplimented to the body as an energy source. ...

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  18. (A) Deficiency of vitamin K causes excessive bleeding in injuries. (...

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  19. (A) Enzyme catalysed hydrolysis of sucrose is faster than acid catalys...

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  20. (A) Insulin is a globular protein. (R) Insulin has two polypeptide c...

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