Classification of Amino Acid

Classification of Amino Acid

Q. 1

With help of the drug shown below, serotonin is synthesized from which of the following precursor amino acid? 

 A

Tyrosine.

 B

Tryptophan.

 C

Phenylalanine.

 D

Glycine.

Q. 1

With help of the drug shown below, serotonin is synthesized from which of the following precursor amino acid? 

 A

Tyrosine.

 B

Tryptophan.

 C

Phenylalanine.

 D

Glycine.

Ans. B

Explanation:

Ans:B.)Tryptophan.

  • Serotonin is synthesized from the essential amino acid tryptophan.
  • The rate-limiting step is the conversion of the amino acid to 5-hydroxytrptophan by tryptophan hydroxylase. 
  • This is then converted to serotonin by the aromatic L-amino acid decarboxylase which needs Pyridoxal Phosphate as a cofactor.

Q. 2

Iso electric pH is :

 A

Point at which all amino acids are in zwitter ion form

 B

Point at which pH of ions are same

 C

Point at which pH of ions does not alter

 D

Point at which positive and negative charges on the amino acid are equal.

Q. 2

Iso electric pH is :

 A

Point at which all amino acids are in zwitter ion form

 B

Point at which pH of ions are same

 C

Point at which pH of ions does not alter

 D

Point at which positive and negative charges on the amino acid are equal.

Ans. D

Explanation:

Q. 3

The amino acid residue having an iminoside chain is:

 A

Lysine

 B

Histidine

 C

Tyrosine

 D

Proline

Q. 3

The amino acid residue having an iminoside chain is:

 A

Lysine

 B

Histidine

 C

Tyrosine

 D

Proline

Ans. D

Explanation:

Ans:D.)Proline.

Proline has a secondary amino group, and hence it is an imino acid.


Q. 4

Sulphur containing amino acid is/are:

 A

Aspartic acid

 B

Glutamine

 C

Methionine

 D

Glycine

Q. 4

Sulphur containing amino acid is/are:

 A

Aspartic acid

 B

Glutamine

 C

Methionine

 D

Glycine

Ans. C

Explanation:

Q. 5

Property of photochromosity is seen amongst the following amino acids:

 A

Unsaturated aminoacid

 B

Aromatic aminoacid

 C

Monocarboxylic acid

 D

Dicarboxylic acid

Q. 5

Property of photochromosity is seen amongst the following amino acids:

 A

Unsaturated aminoacid

 B

Aromatic aminoacid

 C

Monocarboxylic acid

 D

Dicarboxylic acid

Ans. B

Explanation:

Q. 6

Aromatic amino acids are –

 A

Tryptophan

 B

Tyrosine

 C

Phenylalanine

 D

All

Q. 6

Aromatic amino acids are –

 A

Tryptophan

 B

Tyrosine

 C

Phenylalanine

 D

All

Ans. D

Explanation:

Q. 7

Polar amino acid (s) is/are:

 A

Serine

 B

Tyrosine

 C

Lysine

 D

All

Q. 7

Polar amino acid (s) is/are:

 A

Serine

 B

Tyrosine

 C

Lysine

 D

All

Ans. D

Explanation:

Q. 8

Non Polar Amino Acids are:

 A

Alanine

 B

Tryptophan

 C

Isoleucine

 D

All

Q. 8

Non Polar Amino Acids are:

 A

Alanine

 B

Tryptophan

 C

Isoleucine

 D

All

Ans. D

Explanation:

Q. 9

Most non polar Amino Acid is :

 A

Leucine

 B

Glycine

 C

Arginine

 D

Lysine

Q. 9

Most non polar Amino Acid is :

 A

Leucine

 B

Glycine

 C

Arginine

 D

Lysine

Ans. A

Explanation:

Q. 10

Acidic amino acids are –

 A

Asparagine

 B

Arginine

 C

None

 D

Lysine

Q. 10

Acidic amino acids are –

 A

Asparagine

 B

Arginine

 C

None

 D

Lysine

Ans. A

Explanation:

 

Proline is a unique amino acid and has an immino group (=NH) instead of an amino (NH2) group found in other amino acid.

Methionine & Cysteine are sulfur containing aminoacids.

The property of photochromicity (i.e. absorbance of ultraviolet light at 250-290nm esp 280nm) is seen with aromatic amino acid (tryptophan > tyrosine > phenylalanine).

Hydrophobic (non polar) aminoacids have no charge on their R group or side chain. Aliphatic (eg methyl, methylene, thioether & imino) side chains and aromatic side chains are nonpolar. So methyl (CH3) side chain of alanine; propyl (C3H7) side chain of valine; butyl (C4H9) side chain of leuicine & isoleucine; thioether side chain of methionine; and imino group/ pyrrolidine containing side chain of proline are nonpolar.

Methyl (CH3) side chain of alanine is nonpolar. Serine, threonine, tyrosine containing hydroxyl group and cysteine containing sulfhydryl group, are polar aminoacids with neutral/uncharged/nonionic side chain. Positively charged basic amino (NH 3+)group side chain of histidine, arginine and lysine ; and negatively acidic carboxyl (COO-) side chain of aspartic acid and glutamic acid is polar.


Q. 11

Basic amino acids are :

 A

Aspartate and glutamate

 B

Serine and glycine

 C

Lysine and arginine

 D

None of the above

Q. 11

Basic amino acids are :

 A

Aspartate and glutamate

 B

Serine and glycine

 C

Lysine and arginine

 D

None of the above

Ans. C

Explanation:

Q. 12

Most basic amino acid out of the following is :

 A

Alanine

 B

Arginine

 C

Histidine

 D

Lysine

Q. 12

Most basic amino acid out of the following is :

 A

Alanine

 B

Arginine

 C

Histidine

 D

Lysine

Ans. B

Explanation:

Q. 13

Which of these amino acids will migrate slowest to the anode end at the physiological pH?

 A

Aspartic acid

 B

Glycine

 C

Lysine

 D

Valine

Q. 13

Which of these amino acids will migrate slowest to the anode end at the physiological pH?

 A

Aspartic acid

 B

Glycine

 C

Lysine

 D

Valine

Ans. C

Explanation:

 

At physiological pH basic aminoacid (positive charged a.a) will move slowest towards anode (positively charged electrode).

Basic amino acids are: Arginine (Most basic), Lysine and Histidine (Weakly basic)


Q. 14

Non-Essential amino acid is –

 A

Tyrosine

 B

Phenylalanine

 C

Lysine

 D

Threonine

Q. 14

Non-Essential amino acid is –

 A

Tyrosine

 B

Phenylalanine

 C

Lysine

 D

Threonine

Ans. A

Explanation:

Q. 15

An essential amino acid in man is –

 A

L-methionine

 B

L-tyrosine

 C

L-serine

 D

L-proline

Q. 15

An essential amino acid in man is –

 A

L-methionine

 B

L-tyrosine

 C

L-serine

 D

L-proline

Ans. A

Explanation:

Q. 16

All are essential amino acids except-

 A

Phenylalanine

 B

Lysine

 C

Leucine

 D

Glycine

Q. 16

All are essential amino acids except-

 A

Phenylalanine

 B

Lysine

 C

Leucine

 D

Glycine

Ans. D

Explanation:

Q. 17

Semiessential amino acids are-

 A

Arginine

 B

Histidine

 C

Glycine

 D

A and B both

Q. 17

Semiessential amino acids are-

 A

Arginine

 B

Histidine

 C

Glycine

 D

A and B both

Ans. D

Explanation:

Q. 18

Which one of the following amino acids is most likely to be found in the trans membrane region of a protein?

 A

Lysine

 B

Arginine

 C

Leucine

 D

All

Q. 18

Which one of the following amino acids is most likely to be found in the trans membrane region of a protein?

 A

Lysine

 B

Arginine

 C

Leucine

 D

All

Ans. C

Explanation:

 Ans:C.)Leucine.

  • Cell membrane is a complex structure composed of lipid, proteins and carbohydrate. Membrane lipids form bilayer. The unique characteristic of this layer is that it has its hydrophobic ends in the centre of membrane while its hydrophilic ends lie on the outer surface of membrane.
  • Hydrophobhic or Non polar aminoacid are present in transmembrane region. Hydrophillic or polar amino acids are present on outer surface of membrane.
    • Leucine is a hydrophobic a.a so it lies in transmembrane region

Polar Amino Acids (Hydrophilic)
Charged

  • Acidic Amino acids-Aspartic Acid (Aspartate), Glutamic Acid (Glutamate)
  • Basic Amino Acids-Histidine, Arginine,Lysine

Uncharged

  • Aliphatic amino acid with hydroxyl group as side chain: Serine, Threonine
  • Aliphatic amino acids with amide group: Asparagine, Glutamine
  • Simple Amino acid: Glycine alone
  • Sulfur containing Aminoacid: Cysteine alone.

Nonpolar Amino Acids (Hydrophobic)

  • Simple amino acid: Alanine alone
  • Sulfur containing amino acid: Methionine alone
  • Aromatic Amino acids except Histidine .
  • All branched chain amino acids: Leucine,Isoleucine and Valine
  • Imino acid: Proline

Q. 19

Amino acid which lacks chirality is:

 A

Lysine

 B

Leucine

 C

Histidine

 D

Glycine

Q. 19

Amino acid which lacks chirality is:

 A

Lysine

 B

Leucine

 C

Histidine

 D

Glycine

Ans. D

Explanation:

Q. 20

Optically inactive Amino Acid is

 A

Proline

 B

Glycine

 C

Lysine

 D

Leucine

Q. 20

Optically inactive Amino Acid is

 A

Proline

 B

Glycine

 C

Lysine

 D

Leucine

Ans. B

Explanation:

Ans:B.)Glycine.

  • Amino acids having an asymmetric carbon atom exhibit optical activity. Asymmetry arises when 4 different groups are attached to the same carbon atom .
  • Glycine is the simplest amino acid and has no asymmetric carbon atom and therefore shows no optical activity. All others are optically active.

Q. 21

Most stable amino acid at the physiological pH is:

 A

Histidine

 B

Lysine

 C

Arginine

 D

Glycine

Q. 21

Most stable amino acid at the physiological pH is:

 A

Histidine

 B

Lysine

 C

Arginine

 D

Glycine

Ans. A

Explanation:

Q. 22

Which of the following amino acid is active at neutral pH?

 A

Histidine

 B

Glycine

 C

Arginine

 D

Aspartic acid

Q. 22

Which of the following amino acid is active at neutral pH?

 A

Histidine

 B

Glycine

 C

Arginine

 D

Aspartic acid

Ans. A

Explanation:

Q. 23

Which amino acid can protonate & deprotonate at neutral pH?

 A

Histidine

 B

Leucine

 C

Glycine

 D

All

Q. 23

Which amino acid can protonate & deprotonate at neutral pH?

 A

Histidine

 B

Leucine

 C

Glycine

 D

All

Ans. A

Explanation:

Q. 24

The following is false about Tryptophan

 A

Non essential amino acid

 B

Involved in serotonin synthesis

 C

Involved in niacin synthesis

 D

Involved in melatonin synthesis

Q. 24

The following is false about Tryptophan

 A

Non essential amino acid

 B

Involved in serotonin synthesis

 C

Involved in niacin synthesis

 D

Involved in melatonin synthesis

Ans. A

Explanation:

Q. 25

The amino acid that can be converted into a vitamin

 A

Glycine

 B

Tryptophan

 C

Phenylalanine

 D

Lysine

Q. 25

The amino acid that can be converted into a vitamin

 A

Glycine

 B

Tryptophan

 C

Phenylalanine

 D

Lysine

Ans. B

Explanation:

Q. 26

Which of the following amino acids is involved in the synthesis of thyroxine ?

 A

Glycine

 B

Methionine

 C

Threonine

 D

Tyrosine

Q. 26

Which of the following amino acids is involved in the synthesis of thyroxine ?

 A

Glycine

 B

Methionine

 C

Threonine

 D

Tyrosine

Ans. D

Explanation:

Ans:D.)Tyrosine.

Specialized products from amino acids
Amino acid             Product
Glycine     :    Creatine, glutathione, heme, purines, conjugated bite acids
Tyrosine     :  Thyroxine, epinephrine, nor epinephrine, dopamine, melanin
Tryptophan  :  NAP, NADP, serotonin, melatonin
Methionine :   Creatine, epinephrine, poiyamines
Cysteine    :   Glutathione, taurine, co enzyme-A, active sulfate
Histidine   :   Histamine
Arginine   :   Creatine , nitric oxide
Lysine     :    Carnitine
Glutamate :  GABA, glutathione, gamma- carboxy glutamate
Glutamine :   Purines, pyrimidines, amino sugars
Aspartate  :   Purines, pyrimidines,
Serine      :    Phosphatidyt serine, sphingomyelins, choline
β-Alanine  :   Coenzyme-A


Q. 27

Essential amino acids are A/E –

 A

Leucine

 B

Lysine

 C

Methinnine

 D

Proline

Q. 27

Essential amino acids are A/E –

 A

Leucine

 B

Lysine

 C

Methinnine

 D

Proline

Ans. D

Explanation:

Ans. is `d’ i.e., Proline

Essential amino acids (EAA)

  • Some amino acids cannot be synthesized inside the human body in amounts corresponding to needs.  So, they must be obtained from dietry proteins.
  • These are called essential amino acids ‑
  • These are :Leucine, lsoleucine, lysine. methionine, phenylalunine, threonine,valine,tryptophan and histidine. 
  • A protein is said to be “biologically complete” if it contains all the EAA in amounts corresponding to human needs.
  • Animal proteins are considered to be the superior to vegetable proteins because they are biologically complete. For example milk and egg. proteins have a pattern of amino acids considered most suitable for humans.



Q. 28

Semi essential amino acids are –

 A

Arginine

 B

Lysine

 C

Leucine

 D

All

Q. 28

Semi essential amino acids are –

 A

Arginine

 B

Lysine

 C

Leucine

 D

All

Ans. A

Explanation:

Ans. is ‘a’ i.e., Arginine

Semiessential amino acids

  • Semiessential amino acids are ones that can sometimes be made internally if conditions are right.
  • Arginine and histidine are such amino acids that can be converted from other amino acids.

Also know

Conditionally essential amino acids

  • Non-essential amino acids become essential if their precursors are deficient.
  • Examples —> Tyrosine (derived from pheylalanine) and cysteine (derived from methionine).

Q. 29

Cereal protein is deficient in which amino acid ‑

 A

Leucine

 B

Lysine 

 C

Phenylalanine

 D

Tryptophan

Q. 29

Cereal protein is deficient in which amino acid ‑

 A

Leucine

 B

Lysine 

 C

Phenylalanine

 D

Tryptophan

Ans. B

Explanation:

Ans. is ‘b’ i.e., Lysine 


Q. 30

Limiting amino acid in soyabean is –

 A

Threonine

 B

Lysine 

 C

Methionine

 D

Tryptophan

Q. 30

Limiting amino acid in soyabean is –

 A

Threonine

 B

Lysine 

 C

Methionine

 D

Tryptophan

Ans. C

Explanation:

Ans. is ‘c’ i.e., Methionine 


Q. 31

The amino acid which is associated with atherosclerosis is :

 A

Lysine

 B

Homocysteine

 C

Cysteine

 D

Alanine

Q. 31

The amino acid which is associated with atherosclerosis is :

 A

Lysine

 B

Homocysteine

 C

Cysteine

 D

Alanine

Ans. B

Explanation:

Answer is B (Homocysteine)

  • There is a strong positive correlation between atherosclerosis and circulating levels of Homocysteine’
  • Hyperhomocysteinemia has been most consistently linked with atherosclerosis and coronary thrombotic events
  • “Patient with clinical and angiographic evidence of coronary artery disease tend to have higher levels of plasma homocysteine. The relationship has not been extended to cerebrovascular and peripheral vascular disease”- CMDT
  • “A large body of literature suggests a relationship between hyperhomocysteinemia and coronary events. Several mutations in the enzymes involved in homocysteine accumulation correlate to thrombosis and (in some studies) coronary risk”
  • An increase of 5 micromol / L of homocysteine in serum elevates the risk of coronary artery disease by as much as cholesterol increase of 20 mg /dl.
  • Homocysteine interacts with lysyl residues of collagen interfering with collagen cross linking.
  • It forms homocysteine thiolactone, a highly reactive free radical which thiolates LDL particles.
  • These particles tend to aggregate, are endocytosed by macrophages and increase the tendency for atherogenesis.
  • Providing adequate quantity of pyridoxine, vitamin B12 and folic acid will keep homocysteine in blood in normal levels.
  • Maternal hyperhomocysteinemia is known to increase the chances of neural tube defects in foetus. So, high doses of folic acid are advised in pregnancy.

Q. 32

Essential amino acid is:   

 A

Phenylalanine

 B

Proline

 C

Glutamine

 D

Serine

Q. 32

Essential amino acid is:   

 A

Phenylalanine

 B

Proline

 C

Glutamine

 D

Serine

Ans. A

Explanation:

 

Phenylalanine

  • It is an alpha-amino acid.
  • This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain.
  • L-Phenylalanine (LPA) is an electrically neutral amino acid
  • The codons for L-phenylalanine are UUU and UUC.
  • Phenylalanine is a precursor for tyrosine, the monoamine signaling molecules dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and the skin pigment melanin.

Q. 33

Essential amino acids are named so:       

 A

Because they are produced in the body

 B

Because they are not produced in the body

 C

They are not important for life

 D

Every food stuff essentially contains them

Q. 33

Essential amino acids are named so:       

 A

Because they are produced in the body

 B

Because they are not produced in the body

 C

They are not important for life

 D

Every food stuff essentially contains them

Ans. B

Explanation:

 

Essential amino acids are so called not because they are more important to life than the others, but because the body does not synthesize them, making it essential to include them in one’s diet in order to obtain them. They are Leucine, Arginine, Histidine, Isoleucine, Meyhionine, Phenylalanine, Threonine, Tryptophan, Valine and lysine.

Additionally, cysteine (or sulphur-containing amino acids), tyrosine (or aromatic amino acids), histidine and arginine are required by infants and growing children.


Q. 34

Limiting amino acid in wheat are:  

 A

Lysine, arginine

 B

Threonine, methionine

 C

Lysine, threonine

 D

Lysine, methionine

Q. 34

Limiting amino acid in wheat are:  

 A

Lysine, arginine

 B

Threonine, methionine

 C

Lysine, threonine

 D

Lysine, methionine

Ans. C

Explanation:

 

Limiting amino acid in various food stuffs

Wheat-lysine (the most deficient) and threonine (second limiting amino acid) Rice-lysine

Legumes-tryptophan or methionine (or cysteine)

Maize-lysine and tryptophan

Egg-none; the reference for absorbable protein


Q. 35

Amino acid involved in urea synthesis:

 A

Glutamine

 B

Aspartic acid

 C

Valine

 D

Phenylalanine

Q. 35

Amino acid involved in urea synthesis:

 A

Glutamine

 B

Aspartic acid

 C

Valine

 D

Phenylalanine

Ans. B

Explanation:

Ans:B.)Aspartic Acid 

  • Urea has 2 amino (-NH2) groups, one derived from NH3 and other from aspartate.

UREA CYCLE
• Location: Cytosol and mitochondria of hepatocytes.
• Substrates: NH 3 (as derived from oxidative deamination of glutamate); CO2 ; aspartate; three ATP.

• Products: Urea; fumarate; H2O.

• Purpose: The urea cycle allows for the excretion of NH 4+ by transforming ammonia into urea, which is then excreted by the kidneys.

• Important enzymes:

  • Carbamoyl phosphate synthetase I: Converts ammonium and bicarbonate into carbamoyl phosphate. This is the rate-limiting step in the urea cycle. This reaction requires two ATP and occurs in the mitochondria.
  • Ornithine transcarbamoylase: Combines ornithine and carbamoyl phosphate to form citrulline. Located in mitochondria.
  • Argininosuccinate synthetase: Condenses citrulline with aspartate to form arginosuccinate. This reaction occurs in the cytosol and requires one ATP.
  • Argininosuccinate lyase: Splits argininosuccinate into arginine and fumarate. Occurs in the cytosol.
  • Arginase: Cleaves arginine into one molecule of urea and ornithine in the cytosol. The ornithine is then transported back into the mitochondria for entry back into the cycle.

• Regulation: Carbamoyl phosphate synthetase I catalyzes the rate-limiting step of the cycle and is stimulated by N -acetylglutamate.

• Diseases:

  • Hyperammonemia occurs when there is a deficiency in one of more of the urea cycle enzymes, causing insufficient removal of NH 4+ .
  • Ammonia intoxication leads to CNS deterioration in the form of mental retardation, seizure, coma, and death.

Q. 36

Amino acid which contributes to biosynthesis of purine ribonucleotide are all except:    

 A

Aspartate

 B

Histidine

 C

Glutamine

 D

Glycine

Q. 36

Amino acid which contributes to biosynthesis of purine ribonucleotide are all except:    

 A

Aspartate

 B

Histidine

 C

Glutamine

 D

Glycine

Ans. B

Explanation:

 

Biosynthesis of purine

  • N1 of purine is derived from amino group of aspartate
  • N3 and N9 are obtained from amide group of glutamine
  • C4, C5 and N7 of the purine ring of nucleotides are contributed by glycine



Q. 37

Which of the following correlates well to overcoming of limiting amino acids in diet:       

March 2013

 A

Rancidity

 B

Tertiary structure of

 C

Biological value

 D

Complementary action of proteins

Q. 37

Which of the following correlates well to overcoming of limiting amino acids in diet:       

March 2013

 A

Rancidity

 B

Tertiary structure of

 C

Biological value

 D

Complementary action of proteins

Ans. D

Explanation:

Ans. D i.e. Complementary action of proteins

A varied diet that includes different types of food will contain all the amino acids that an individual needs. If a food lacking in an amino acid is eaten with another food which contains it, then the second food compensates for the first and vice versa. This is called the complementary action of proteins


Q. 38

Neutral amino acid is ‑

 A

Arginine

 B

Lysine

 C

Aspartate

 D

Leucine

Q. 38

Neutral amino acid is ‑

 A

Arginine

 B

Lysine

 C

Aspartate

 D

Leucine

Ans. D

Explanation:

Q. 39

Not an essential amino acid ‑

 A

Arginine

 B

Histidine

 C

Glutamate

 D

Lysine

Q. 39

Not an essential amino acid ‑

 A

Arginine

 B

Histidine

 C

Glutamate

 D

Lysine

Ans. C

Explanation:

Q. 40

Amino acid which is optically inert ‑

 A

Valine

 B

Alanine

 C

Glycine

 D

Threonine

Q. 40

Amino acid which is optically inert ‑

 A

Valine

 B

Alanine

 C

Glycine

 D

Threonine

Ans. C

Explanation:

 

The a-carbon of amino acids has four different groups attached to it and so is a chiral or asymmetric carbon.

Hence, there are two possible enantiomers, L and D, i.e., mirror image with refrence to a-carbon.

The chiral carbon is also responsible for optical activity and stereoisomerism.

Only exception is glycine, which is the simplest amino acid.

Glycine has no chiral carbon (chirality) because a-carbon of glycine does not have four different groups attached to it.

Therefore glycine does not have optical activity or D and L forms (enantiomers).


Q. 41

Amino acids with extra NH; (amino group) in strucuture

 A

Aspartate

 B

 Glutamate

 C

Histidine

 D

Alanine

Q. 41

Amino acids with extra NH; (amino group) in strucuture

 A

Aspartate

 B

 Glutamate

 C

Histidine

 D

Alanine

Ans. C

Explanation:

Q. 42

Fumarate of TCA is derived from transmination of which amino acid

 A

Phenylalanine

 B

Methionine

 C

Valine

 D

Glutamine

Q. 42

Fumarate of TCA is derived from transmination of which amino acid

 A

Phenylalanine

 B

Methionine

 C

Valine

 D

Glutamine

Ans. A

Explanation:

Q. 43

Which of the following amino acids is purely ketogenic‑

 A

Phenylalanine

 B

Leucine

 C

Proline

 D

Tyrosine

Q. 43

Which of the following amino acids is purely ketogenic‑

 A

Phenylalanine

 B

Leucine

 C

Proline

 D

Tyrosine

Ans. B

Explanation:

Ans:B.)

Amino acids:

Ketogenic :

  • Leucine, Lysine

Glucogenic:

  • Valine, Cysteine, Serine,Alanine, Histidine,Threonine, Arginine, Glycine, Glutamate, Proline/Hydroxy proline

Both Glucogenic & Ketogenic :

  • Isoleucine, Tyrosine ,Tryptophan , Phenylalanine

Q. 44

Which of the following glucogenic amino acid enters the citric acid cycle at succinyl CoA

 A

Phenylalanine

 B

Tyrosine

 C

Isoleucine

 D

Tryptophan

Q. 44

Which of the following glucogenic amino acid enters the citric acid cycle at succinyl CoA

 A

Phenylalanine

 B

Tyrosine

 C

Isoleucine

 D

Tryptophan

Ans. C

Explanation:

Ans. is ‘c’ i.e., isoleucine


Q. 45

Glucogenic amino acid is ‑

 A

Leucine

 B

Leucine

 C

Glutamine

 D

None

Q. 45

Glucogenic amino acid is ‑

 A

Leucine

 B

Leucine

 C

Glutamine

 D

None

Ans. C

Explanation:

Ans. is ‘c’ i.e., Glutamine

Glucogenic

  • Alanine
  • Arginine
  • Aspargine
  • Aspartic acid
  • Cysteine
  • Glutamine
  • Glutamic acid
  • Glycine
  • Histidine
  • Methionine
  • Proline
  • Serine
  • Threonine
  • Valine

Ketogenic

  • Leucine
  • Lysine

Both glucogenic & ketogenic

  • Isoleucine
  • Phenylalaine
  • Tyrosine
  • Tryptophan

Note : According to Harper 29th/e (P-282), lysine is both ketogenic and glucogenic. But all other textbooks have mentioned it as ketogenic.


Q. 46

Which Branched chain amino acid is ketogenic‑

 A

Lycine

 B

Leucine

 C

Isoleucine

 D

b and c both

Q. 46

Which Branched chain amino acid is ketogenic‑

 A

Lycine

 B

Leucine

 C

Isoleucine

 D

b and c both

Ans. D

Explanation:

Ans. is `b > c’ i.e., Leucine > Isoleucine

Branched chain amino acids are leucine, Isoleucine and valine.

1) Leucine is purely ketogenic.

2) Isoleucine is both ketogenic and glucogenic.

3) Valine is glucogenic.


Q. 47

Branched chain amino acid which is both ketogenic and glucogenic ‑

 A

Leucine

 B

Isoleucine

 C

Valine

 D

Tryptophan

Q. 47

Branched chain amino acid which is both ketogenic and glucogenic ‑

 A

Leucine

 B

Isoleucine

 C

Valine

 D

Tryptophan

Ans. B

Explanation:

Ans. is ‘b’ i.e., Isoleucine


Q. 48

True about charge in amino acid ‑

 A

Carboxyl group can form positive charge

 B

Amino group can form negative charge

 C

Neutral at isoelectric pH

 D

All of the above

Q. 48

True about charge in amino acid ‑

 A

Carboxyl group can form positive charge

 B

Amino group can form negative charge

 C

Neutral at isoelectric pH

 D

All of the above

Ans. C

Explanation:

Ans. is ‘c’ i.e., Neutral at isoelectric pH

The pH value at which the number of positive charges equals the number of negative charges is isoelectric pH of amino acids.

At its isoelectric pH, an amino acid is in zwitterion form (dipolar molecule), i.e. has both positive and negative charge on same acid, but overall molecule is electrically neutral.

  • The carboxy (-COON) group of an amino acid can donate protein (Er) and behave as an acid forming a negatively charged anion (coo).
  • Amino group (-N1-12) can accept proton (I-1+) and behave as a base, forming positively charged cation (NH3′).

Amphoteric property of amino acid

  • Substances having a two-way property are called amphoteric or ampholyte. Amino acids have both acidic and basic groups, i.e., they can donate a proton or accept a proton, hence amino acids are referred to as amphoteric. Amphoteric property is related to : ‑

Zwitterion or dipolar molecule

  •  Monoamine-Monocarboxylic amino acids exist as dipolar ion or zwitterions, i.e., they have both positive and negative charges on the same amino acids.
  • The a-COOH group donate its proton to amino group (-NH2) and becomes negatively charged anion (C00).
  • The a-NH2 group accepts proton from carboxyl group (a-COOH) to form positively charged cation (NH3′).
  • The overall molecule (zwitterion) is electrically neutral, i.e., the molecular species which contain an equal number of ionizable group of opposite charge and as a result bear no charge (are neutral) are called zwitterions.

Q. 49

Side chain of which amino acid contains sulfhydryl group ‑

 A

Aspargine

 B

Cysteine

 C

Isoleucine

 D

Threonine

Q. 49

Side chain of which amino acid contains sulfhydryl group ‑

 A

Aspargine

 B

Cysteine

 C

Isoleucine

 D

Threonine

Ans. B

Explanation:

Ans. is ‘b’ i.e., Cysteine

There are two sulfur containing amino acids :-

i) Cysteine

ii) Methionine

The side chain of cysteine contains sulfhydryl group that has a pKa of approximately 8.4 for dissociation of its hydrogen sulfhydryl groups of two cystein molecules can form covalent disulfide bond to form cystine.

Methionine although it contains sulfur group, does not containt sulfhydryl group and cannot form disulfide bond.


Q. 50

Taurine seen in bile acid metabolism is synthesized from which amino acid ‑

 A

Serine

 B

Cysteine

 C

Methionine

 D

Glycine

Q. 50

Taurine seen in bile acid metabolism is synthesized from which amino acid ‑

 A

Serine

 B

Cysteine

 C

Methionine

 D

Glycine

Ans. B

Explanation:

Ans. is ‘b’ i.e., Cysteine

Taurine is synthesized from cysteine.

Synthesis of other important amino acid is as follows :‑

  1. Glutamate is synthesized from a-ketoglutarate by enzyme glutamate dehydrogenase.
  2. Glutamine is synthesized from glutamate by enzyme glutamine synthase.
  3. Alanine is synthesized from pyruvate by transamination.
  4. Aspartate is synthesized from oxaloacetate by transamination.
  5. Asparagine is synthesized from aspartate by enzyme asparagine synthase.
  6. Serine is synthesized from 3-phosphoglycerate (a glycolytic intermediate). It can also be synthesized from glycine as conversion of serine to glycine is reversible.
  7. Glycine is synthesized from (i) glyoxylate and glutamate or alanine; (ii) choline; and (iii) serine
  8. Proline is synthesized from glutamate
  9. Cysteine is synthesized from methionine and serine
  10. Tyrosine is synthesized from phenylalanine.

Q. 51

Niacin is derived from which amino acid?

 A

Tyrosine

 B

Phenylalanine

 C

Tryptophan

 D

Methionine

Q. 51

Niacin is derived from which amino acid?

 A

Tyrosine

 B

Phenylalanine

 C

Tryptophan

 D

Methionine

Ans. C

Explanation:

Q. 52

Glucogenic amino acid is transported to the liver most commonly by

 A

Alanine

 B

Glycine

 C

Lysine

 D

Leucine

Q. 52

Glucogenic amino acid is transported to the liver most commonly by

 A

Alanine

 B

Glycine

 C

Lysine

 D

Leucine

Ans. A

Explanation:

Q. 53

Amino acid with aliphatic side chain

 A

Serine

 B

Alanine

 C

Threonine

 D

Aspartate

Q. 53

Amino acid with aliphatic side chain

 A

Serine

 B

Alanine

 C

Threonine

 D

Aspartate

Ans. B

Explanation:

 

Amino acids are classified as : ‑

1) Aliphatic amino acids : – Alanine, glycine, isoleucine, leucine, valine.

2) Hvdroxy amino acids : – Serine, threonine, tyrosine.

3) Sulfur containing amino acids : – Cysteine, methionine.

4) Dicarboxylic amino acids : – Aspartic acid (aspartate), glutamic acid (glutamate).

5) Amide containing amino acids : – Glutamine, aspargine (these are amides of dicarboxylic amino acids. Glutamine is amide of glutamic acid and aspargine is amide of aspartic acid).

6) Aromatic amino acids : – Phenylalanine, tyrosine, tryptophan.

7) Imino acids or heterocyclic amino acids : – One of the 20 amino acids, proline is an imino (-NH) acid not an amino (-NH2) acid, as are other 19.


Q. 54

Nitric oxide is derived from which amino acid‑

 A

Histidine

 B

Lysine

 C

Methionine

 D

Arginine

Q. 54

Nitric oxide is derived from which amino acid‑

 A

Histidine

 B

Lysine

 C

Methionine

 D

Arginine

Ans. D

Explanation:

Ans:D.)Arginine.

NITRIC OXIDE (NO)/ENDOTHELIUM DERIVED RELAXING FACTOR (EDRF)

  • Nitric oxide, a vasodilator is formed by the action of nitric oxide synthase on Arginine. Synthesis:
  • NO is formed by the action of Cytosolic enzyme NO synthase in endothelial & neuronal cells.
  • Substrate: Arginine, O 2 , NADPH
  • Coenzyme: NADPH, FAD, FMN, Heme, tetrahydrobiopterin
  • Product: Citrulline, NO

Features

  • Reacts with oxygen & superoxide  peroxynitrite which decomposes to form highly reactive OH-radical
  • It stimulates guanyl cyclase (cGMP)

Functions

  • Relaxes smooth muscles
  •  Prevents platelet aggregation
  • Functions as neurotransmitter in brain
  • Mediates tumoricidal, bactericidal actions of macrophages
  • Involved in penile erection; (sildenafil affects this process by inhibiting a cGMP dependent phosphodiesterase)

Q. 55

Aromatic amino acid is ‑

 A

Serine

 B

Histidine

 C

Leucine

 D

Tryptophan

Q. 55

Aromatic amino acid is ‑

 A

Serine

 B

Histidine

 C

Leucine

 D

Tryptophan

Ans. D

Explanation:

 Ans:D.)Tryptophan.

CLASSIFICATION OF L-α AMINO ACIDS ON THE BASIS OF SIDE CHAINS

  • Aliphatic Side Chains : Glycine, Alanine, Valine, Leucine, Isoleucine
  • Side Chains Containing Hydroxyl (OH) Groups  :Serine, Threonine, Tyrosine
  • Side Chains Containing Sulphur Atoms  :Cysteine, Cystine, Methionine
  • Side Chains Containing Acidic Groups or their amides  : Aspartic acid, Asparagine, Glutamic acid, Glutamine
  • Side Chains Containing Basic Groups  : Arginine, Lysine, Histidine
  • Containing Aromatic Rings  : Phenylalanine, Tyrosine, Tryptophan

Q. 56

Purely glucogenic amino acid ‑

 A

Isoleucine

 B

Tyrosine

 C

Lysine

 D

Proline

Q. 56

Purely glucogenic amino acid ‑

 A

Isoleucine

 B

Tyrosine

 C

Lysine

 D

Proline

Ans. D

Explanation:

Q. 57

Cereals are rich in which amino acid ‑

 A

Lysine

 B

Threonine

 C

Tiyptophan

 D

Methionine

Q. 57

Cereals are rich in which amino acid ‑

 A

Lysine

 B

Threonine

 C

Tiyptophan

 D

Methionine

Ans. D

Explanation:

Ans. is ‘d’ i.e., Methionine

“Pulses have high lysine content and are deficient in methionine; on the other hand cereals have an abundance of methionine”


Q. 58

Cereal protein is deficient in which amino acid ‑

 A

Leucine

 B

Lysine

 C

Phenylalanine

 D

Tryptophan

Q. 58

Cereal protein is deficient in which amino acid ‑

 A

Leucine

 B

Lysine

 C

Phenylalanine

 D

Tryptophan

Ans. B

Explanation:

Ans. is ‘b’ i.e., Lysine

Supplementary action of proteins

  • Cereals are deficient in essential amino acid Lysine & threonine.
  • Pulses are deficient in essential amino acid Methionine.
  • So if cereals are eaten with pulses, their proteins complement each other & provide a more balanced and complete protein intake.

Q. 59

Cereal protein is deficient in which amino acid

 A

Leucine

 B

Lysine

 C

Phenylalanine

 D

Tryptophan

Q. 59

Cereal protein is deficient in which amino acid

 A

Leucine

 B

Lysine

 C

Phenylalanine

 D

Tryptophan

Ans. B

Explanation:

Ans. is ‘b’ i.e., Lysine

Supplementary action of proteins

  • Cereals are deficient in essential amino acid Lysine & threonine.
  • Pulses are deficient in essential amino acid Methionine.
  • So if cereals are eaten with pulses, their proteins complement each other & provide a more balanced and complete protein intake.

Q. 60

Amino acid deficient in both Wheat and Maize ‑

 A

Lysine

 B

Threonine

 C

Tryptophan

 D

Methionine

Q. 60

Amino acid deficient in both Wheat and Maize ‑

 A

Lysine

 B

Threonine

 C

Tryptophan

 D

Methionine

Ans. A

Explanation:

Ans. is ‘a’ i.e., Lysine

Wheat

  • Next to rice, wheat is the most important cereal.
  • The limiting amino acids in wheat proteins are lysine and threonine.

Q. 61

Amino acid with double chiral is ‑

 A

Phenyalanine

 B

Threonine

 C

Tryptophane

 D

Tyrosine

Q. 61

Amino acid with double chiral is ‑

 A

Phenyalanine

 B

Threonine

 C

Tryptophane

 D

Tyrosine

Ans. B

Explanation:

Ans. is ‘b’ i.e., Threonine 

  • The a-carbon of amino acids has four different groups attached to it and so is a chiral or asymmetric carbon. 
  • All amino acids have one chiral carbon, except –
  • Li Amino acid with no chiral carbon      Glycine.
  • u Amino acid with two chiral centers    Threonine isoleucine.

Q. 62

Neutral amino acid is ‑

 A

Aspartate

 B

Arginine

 C

Glycine

 D

Histidine

Q. 62

Neutral amino acid is ‑

 A

Aspartate

 B

Arginine

 C

Glycine

 D

Histidine

Ans. C

Explanation:

Ans. is ‘c’ i.e., Glycine 

  • Neutral amino acids
  • Alanine Asparging
  • Cysteine Glycine Glutamine Isoleucine
  • Leucine Methionine
  • Proline Phenylalanine
  • Serine
  • Threonine
  • Tyrosine Tryptophan
  • Valine

Q. 63

Essential amino acid is ‑

 A

Alanine

 B

Serine

 C

Arginine

 D

Proline

Q. 63

Essential amino acid is ‑

 A

Alanine

 B

Serine

 C

Arginine

 D

Proline

Ans. C

Explanation:

Ans. is ‘c’   i.e., Arginine 

Nutritionally Essential

Nutritionally Nonessential

Arginine

Alanine

Histidine

Asparagine 

Isoleucine Leucine

Asparatate

Lysine

Cysteine
Methionine Phenylalanine  Glutamate
Threonine Tryptophan Valine Glutamine
  Glycine
   Proline
   Serine
  Tyrosine 

Q. 64

Polar amino acids are all except ‑

 A

Glutamic acid

 B

Histidine

 C

Glutamine

 D

Methionine

Q. 64

Polar amino acids are all except ‑

 A

Glutamic acid

 B

Histidine

 C

Glutamine

 D

Methionine

Ans. D

Explanation:

Ans. is ‘d’ i.e., Methionine


Q. 65

Ninhydrin test is used for ‑

 A

Bile salts

 B

Amino acids

 C

Nucleic acid

 D

Lipids

Q. 65

Ninhydrin test is used for ‑

 A

Bile salts

 B

Amino acids

 C

Nucleic acid

 D

Lipids

Ans. B

Explanation:

Ans. is ‘b’ i.e., Amino acids 

Important chemical reactions of amino acids

  • Following are some important chemical reactions.

A.  Reaction used to determine amino acid sequence in polypeptide chain : – Generally, amino terminal (N-terminal) of amino acid is tagged with some reagent. It is split off by hydrolysis and tagged amino acid is identified. The reaction is, then, repeated with new N-terminal of subsequent amino acid and so on. The two reactions are used for identification of amino acid sequence : ‑

  • Sanger’s reaction : – Uses Sanger’s reagent ( 1 -fluoro-2,4-dinitrobenzene) to tag amino terminal.
  • Edman’s reaction : – Uses Edman’s reagent (phenylisothiocyanate) to tag amino terminal.

B.  Reaction used to identification of individual or group of amino acids : – These reactions are frequently used for qualitative detection and quantitative measurement of various amino acids.

  • Ninhydrin tese : – All a-amino acids.
  • Xanthophoretic reaction : – Aromatic amino acidse (Tyrosine, tryptophan, phenylalanine).
  • Millan’s teste (Millon-Nasse reaction) : – Tyrosine° (phenol group of tyrosine). Therefore millon’s test is positive in tyrosinosis°.
  • Aldehyde test : – Tryptophan (indole ring)
  • Hopkins-tole reaction : – Tryptophan (indole ring)
  • Sakaguch’s reaction : – Arginine (guanidinium group of arginine).
  • Sulphur test : – Cysteine (sulphydryl group)
  • Nitroprusside test : – Cysteine (sulphydryl group)
  • Pauly’s test : – Histidine (imidazole group)
  • Biuret reaction : – Peptide bond
  • Diazo reaction Q (Pauli’s) : – Histidine or tyrosine.

Q. 66

Essential amino acid amongst the following ‑

 A

Arginine

 B

Lysine

 C

Threonine

 D

All

Q. 66

Essential amino acid amongst the following ‑

 A

Arginine

 B

Lysine

 C

Threonine

 D

All

Ans. D

Explanation:

Ans. is ‘d’ i.e., All


Q. 67

Amino acid with double chiral is ‑

 A

Phenyalanine

 B

Threonine

 C

Tryptophane

 D

Tyrosine

Q. 67

Amino acid with double chiral is ‑

 A

Phenyalanine

 B

Threonine

 C

Tryptophane

 D

Tyrosine

Ans. B

Explanation:

Ans. is ‘b’ i.e., Threonine 


Q. 68

Amino acid required for formation of thyroxine‑

 A

Tryptophan

 B

Tyrosine

 C

Glutamine

 D

Cysteine

Q. 68

Amino acid required for formation of thyroxine‑

 A

Tryptophan

 B

Tyrosine

 C

Glutamine

 D

Cysteine

Ans. B

Explanation:

Ans. is ‘b i.e., Tyrosine

  • The term thyroid hormone denotes both thyroxine (7′4) and triodothyronine (T3).
  • Both T4 and T3 are iodine derivatives of thyronine.
  • Thyronine is a condensation product of two molecules of amino acid tyrosine.
  • Thyroxine is 3, 5, 3′, 5′ – tetraiodothyronine and T3 is 3, 5, 3 ‘-triiodothyronine.
  • Thyroid hormones are synthesized and stored in the thyroid follicles as apart of thyroglobulin molecule.

Q. 69

Amino acid connot be used for glycogen synthesis 

 A

Alanine

 B

Threonine

 C

Leucine

 D

Methionine

Q. 69

Amino acid connot be used for glycogen synthesis 

 A

Alanine

 B

Threonine

 C

Leucine

 D

Methionine

Ans. C

Explanation:

Ans. is ‘c’ i.e., Leucine 

  • Synthesis of glucose from non-carbohydrate precursors is called gluconeogenesis.
  • When the end product is glycogen instead of glucose, the process is called glyconeogenesis, i.e., synthesis of glycogen from noncarbohydrate precursors.
  • Terms gluconeogenesis and glyconeogenesis are used interchangeably as all reactions are same except for last where glucose-6-phosphate enters the glycogen synthesis pathway, instead by being converted to glucose. Coming back to question
  • Alanine, threonine and methionine are glucogenic amino-acids, i.e. can be used as substrates for gluconeogenesis or glyconeogenesis.
  • Leucine is purily ketogenic amino acid, can not be used as a substrate for gluconeogenesis or glyconeogenesis.

Q. 70

Amino acid with aliphatic side chain ‑

 A

Serine

 B

Leucine

 C

Threonine

 D

Aspartate

Q. 70

Amino acid with aliphatic side chain ‑

 A

Serine

 B

Leucine

 C

Threonine

 D

Aspartate

Ans. B

Explanation:

Ans. is ‘b’ i.e., Leucine

  • Based on chemical sturcture of side chain, amino acids are classified into ‑
  1. Aliphatic amino acids : – Alanine, glycine, isoleucine, leucine, valine.
  2. Hydroxy amino acids : – Serine, threonine, tyrosine.
  3. Sulfur containing amino acids : – Cysteine, methionine.
  4. Dicarboxylic amino acids : – Aspartic acid (aspartate), glutamic acid (glutamate).
  5. Amide containing amino acids : – Glutamine, aspargine (these are amides of dicarboxylic amino acids. Glutamine is amide of glutamic acid and aspargine is amide of aspartic acid).
  6. Aromatic amino acids : – Phenylalanine, tyrosine, tryptophan.
  7. Imino acids or heterocyclic amino acids : – One of the 20 amino acids, proline is an imino (-NH) acid not an amino (-NH) acid, as are other 19.

Q. 71

Limiting amino acid in maize ‑

 A

Lysine

 B

Threonine

 C

Methionine

 D

Arginine

Q. 71

Limiting amino acid in maize ‑

 A

Lysine

 B

Threonine

 C

Methionine

 D

Arginine

Ans. B

Explanation:

Ans. is ‘a’ i.e., Lysine 

Food             Limiting amino acids

Wheat           Lysine and threonine

Maize           Tryptophan and lysine

Pulses          Methionine and to a lesser extent cystein



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