Amino Acids

Q.

What is repeating unit of protein?

Q. Which of the following amino acids has the most basic side chain?

1. Glutamine
2. Methionine
3. Tyrosine
4. Arginine

Q. Amino acids are formed by:

1. Proteins
2. Fatty acids
3. Essential oils
4. $\alpha$-Keto acids

Q.

The number of tripeptides formed by 3 different amino acids is:

1. Five

2. Six

3. Three

4. Four

Q. The non-essential amino acid among the following is:

1. Valine
2. Leucine
   
3. Alanine
4. Lysine

Q. The non-essential amino acid among the following is:

1. Valine
2. Leucine
   
3. Alanine
4. Lysine

Q.

Which of the following is not a sex hormone?

1. Estrone

2. Estradiol

3. Cortisone

4. Testosterone

Q.

Which of the following is not an essential amino acid

1. Valine

2. Lysine

3. Histidine

4. Glycine

Q. At the isoelectric point for an amino acid, the species present are:

1. $R-\underset{N{H}_2}{\underset{|}{CH}}-COOH$
2. $R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-COOH$
3. $R-\underset{N{H}_2}{\underset{|}{CH}}-CO{O}^{-}$
4. $R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-CO{O}^{-}$

Q.

Among the following essential amino acids are

I) Glycine II) Alanine III) Valine IV) Leucine

1. I&II

2. II&III

3. III&IV

4. I&IV

Q.

Which of the following is not essential amino acid?

1. R

2. T

3. S

4. W

Q. The substituents R₁ and R₂ for nine peptides are listed in the table given below. How many of these peptides are positively charged at Ph = 7.0? ___

Q.

A tripeptide is composed equally of L - valine, L - tyrosine and L - alanine (one molecule each).The number of isomeric tripeptides of this kind may exist is

1. 4

2. 5

3. 6

4. 7

Q.

All common amino acids except one react with cold nitrous acid(HNO₂) and evolve nitrogen gas.

That amino acid is

1. Cysteine

2. Proline

3. Histidine

4. None of these

Q. If $K_{a1}$ and $K_{a2}$ are the ionization constants of $H_3{N}^{+}CHICOOH$ and $H_3{N}^{+}CHICO{O}^{-},$ respectively, the pH of the solution at the isoelectric point is

1. $pH=p{K}_{a1}+p{K}_{a2}$
2. $pH=(p{K}_{a1}+p{K}_{a2}{)}^{1/2}$
3. $pH=(p{K}_{a1}+p{K}_{a2}{)}^{1/2}$
4. $pH=\frac{(p{K}_{a1}+p{K}_{a2})}{2}$

Q. What is the monomer of polypeptide?

1. Amino acid
2. Glucose
3. Nucleoside
4. Nucleotide

Q. The increasing order of $p{k}_a$ for the following amino acids (Gly, Asp, Lys, Arg) in aqueous solution is:

1. Asp<Gly<Arg<Lys
2. Arg<Lys<Gly<Asp
3. Gly<Asp<Arg<Lys
4. Asp<Gly<Lys<Arg

Q.

In glycyl alanine the number of sp³ and sp² hybridised carbons respectively

1. 3& 2

2. 5 &0

3. 5 & 2

4. 4&1

Q.

Which of the following statements is correct with respect to all amino acids? They are:

1. All optically active

2. All optically active, except glycine

3. All optically active, except lysine

4. All optically active except glutamic acid

Q. An example of a sulphur containing amino acid is

1. Lysine
2. Serine
3. Cysteine
4. Tyrosine

Q. The predominant form of histamine present in human blood is:
$(pKa=6.0)$

1. 
2. 
3. 
4. 

Q.

A mixture of two amino acids having pl 9.60 and 5.40 can be separated

1. By adjusting the pH of the solution at 9.60

2. By adjusting the pH of the solution at 4.20

3. By adjusting the pH of the solution at 7.0

4. By adjusting the pH of the solution at 7.5

Q. For $\alpha$-amino acids having the structure $R-\underset{N{H}_2}{\underset{|}{C}H}-COOH$

Which of the following statements are true?

A. Water solubility is maximum at a pH when concentrations of anions and cations are equal
B. They give ninhydrin test
C. On reacting with nitrous acid they give off $N_2$

1. All
2. B and C
3. A and B
4. only A

Q.

Which of the nitrogen of histidine is first protonated ?

1. $\alpha$

2. $\beta$

3. $Both$

4. $None$

Q.

The total number of distinct naturally occurring amino acids obtained by complete acidic hydrolysis of the peptide shown below is___

Q. For $\alpha$ - amino acid having the structure,
$R-\underset{N{H}_2}{\underset{|}{CH}}-C{O}_{2}H$

Which of the following statements are true?
(A) Water solubility is maximum at a pH when the concentration of anions and cations are equal.
(B) They give ninhydrin test.
(C) On reacting with nitrous acid, they give of $N_2$.

1. All
2. B and C
3. A and B
4. None of these

Q.

Which of the nitrogen of histidine is first protonated ?

1. $\alpha$

2. $\beta$

3. $Both$

4. $None$

Q.

In alkaline medium, glycine predominantly exists as/in a/an:

1. Cation

2. Anion

3. Zwitter ion

4. Covalent form

Q. $\underset{\left(C_3{H}_{7}N{O}_3\right)}{\left(A\right)\alpha -\text{Amino acid}}\underset{HCl}{\overset{MeOH}{\to }}\underset{\left(C_4{H}_{10}N{O}_{3}Cl\right)}{\left(B\right)}\stackrel{PC{l}_5}{\to }\underset{\left(C_4{H}_{9}N{O}_{2}C{l}_2\right)}{\left(C\right)}$

$\underset{\left(C_4{H}_{9}N{O}_{2}C{l}_2\right)}{\left(C\right)}\stackrel{H_3{O}^{+}}{\to }\underset{\left(C_3{H}_{6}N{O}_{2}Cl\right)}{\left(D\right)}\underset{HCl}{\overset{Na-Hg}{\to }}\text{Alanine}$

Compound (B) is

1. 
2. 
3. 
4. 

Q. $\underset{\left(C_3{H}_{7}N{O}_3\right)}{\left(A\right)\alpha -\text{Amino acid}}\underset{HCl}{\overset{MeOH}{\to }}\underset{\left(C_4{H}_{10}N{O}_{3}Cl\right)}{\left(B\right)}\stackrel{PC{l}_5}{\to }\underset{\left(C_4{H}_{9}N{O}_{2}C{l}_2\right)}{\left(C\right)}$

$\underset{\left(C_4{H}_{9}N{O}_{2}C{l}_2\right)}{\left(C\right)}\stackrel{H_3{O}^{+}}{\to }\underset{\left(C_3{H}_{6}N{O}_{2}Cl\right)}{\left(D\right)}\underset{HCl}{\overset{Na-Hg}{\to }}\text{Alanine}$

Compound (C) is :

1. 
2. 
3. 
4.