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Amino acids structure and properties q and a

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  • 1. Q. How do you classify amino acids?A. Based on the structure, amino acids are classified into: Simple amino acids,Branched chain amino acids, Hydroxy amino acids, Sulfur containing amino acids,Amino acids with amide group, Acidic amino acids, Basic amino acids, Aromaticamino acids, Heterocyclic amino acids, Imino acid and Derived amino acids.Q. What are branched chain amino acids?A. Valine, leucine and isoleucine.Q. What are hydroxy amino acids?A. Serine and threonine.Q. Name the Sulfur containing amino acids.A. Cysteine and methionine.Q. Name the acidic amino acids.A. Aspartic acid and glutamic acid.Q. What are the basic amino acids?A. Lysine and arginine.Q. Which amino acid has a net positive charge at physiological pH?A. Arginine and lysine.Q. Amino acid containing a thioether bond is.A. Methionine.Q. Give examples of amino acids with hydrophobic side chains.A. Valine, leucine, isoleucine.Q. Give the names of aromatic amino acids.A. Phenylalanine and tyrosine.Q. What are heterocyclic amino acids?A. Tryptophan and histidine.Q. Give an example of an imino acid.A. Proline. Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com
  • 2. Q. Give examples of derived amino acids.A. Hydroxy proline, hydroxy lysine, ornithine, citrulline, homocysteine.Q. Arginine contains which special group?A. Guanidinium group (-NH-CNH-NH2).Q. Benzene group is present in which amino acid?A. Phenyl alanine.Q. Phenol group is present in which amino acid?A. Tyrosine.Q. Tryptophan contains what special group?A. Indole group.Q. Which special group is present in Histidine?A. Imidazole group.Q. Name some hydrophobic amino acids.A. Valine, leucine and isoleucine.Q. Pyrrolidine group is present in which amino acid?A. Proline.Q. Hydrophobic bonds are formed in protein between which amino acids?A. Valine, leucine and isoleucine residues.Q. What is the basis of classification of amino acids into ketogenic andglucogenic?A. Ketogenic amino acids enter into the metabolic pathway of fats, while glucogenicamino acids enter the pathway of glucose metabolism.Q. Name a purely ketogenic amino acid.A. Leucine.Q. Name some glucogenic amino acids.A. Glycine; serine; aspartic Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com
  • 3. Q. Which amino acid is synthesised after it gets incorporated into the protein?A. Hydroxyproline .Q. What are essential amino acids?A. They cannot be synthesized in the body; and so, they are to be provided in the diet.Q. How many amino acids are essential?A. Eight amino acids are essential; two are semi-essential and the rest 10 are non-essential.Q. Are non-essential amino acids necessary for the body?A. They are also necessary for protein synthesis, but they can be synthesized by thebody and need not be essentially present in the dietQ. Name any three essential amino acids.A. Isoleucine, leucine, threonine.Q. Is phenyl alanine an essential amino acid?A. Yes.Q. What about Tyrosine?A. Tyrosine is non-essential; it is synthesized from phenyl alanine.Q. Name the semi-essential amino acids.A. Histidine and arginine.Q. Why are they called semi-essential?A. Because growing children require them in food. But they are not essential for theadult individual.Q. What is iso-electric point?A. The pH at which the molecule carries no net charge is called iso-electric point.Q. What are the characteristic features of iso-electric pH.?A. At iso-electric point the amino acid will carry no net charge; there is no mobility inelectrical field, solubility will be minimum, the tendency for precipitation will bemaximum Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com
  • 4. Q. What is the speciality of Histidine?A. The pK value of Histidine is 6.1, and therefore effective as a buffer at thephysiological pH of 7.4. The buffering capacity of plasma proteins and hemoglobin ismainly due to histidine residue.Q. Which is the amino acid having maximum buffering capacity at physiologicalpH?A. Histidine.Q. Which amino acid is optically inactive?A. Glycine.Q. What are the isomers of amino acids?A. D and L varieties.Q. What are natural amino acids?A. Only L amino acids are seen in large quantities in nature.Q. Can you name some substances where D-amino acids are seen?A. D-amino acids are seen in cell walls of micro-organisms and as constituents ofcertain antibiotics such as gramicidin-S, polymyxin, actinomycin-D and valinomycinQ. What is meant by decarboxylation of an amino acid?A. The carboxyl group is removed from the amino acids to form the correspondingamineQ. Give examples of decarboxylation reactions.A. Histidine to histamine; tyrosine to tyramine; tryptophan to tryptamine.Q. What is produced when Glutamic acid is decarboxylated?A. Gamma amino butyric acid or GABA.Q. What is glutamine?A. That is the amide of glutamic acid.Q. What is an amide?A. The extra carboxyl group (other than alpha carboxyl) can combine with ammoniato form the corresponding amide Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com
  • 5. Q. How asparagine is produced?A. Aspartic acid + ammonia will form asparagine.Q. What is transamination?A. The alpha amino group of amino acid can be transferred to alpha keto acid to formthe corresponding new amino acid and alpha keto acidQ. Give an example of transamination reaction.A. Glutamic acid + pyruvic acid alpha keto glutarate + alanine.Q. What is the product of transamination reaction of pyruvate with glutamate?A. Alanine and alpha keto glutarateQ. What is the biological significance of transamination reaction?A. These are important for the inter conversion of amino acids. Non-essential aminoby this processQ. What is the clinical significance of transaminases?A. Transaminases in blood are elevated in liver and heart diseases.Q. What is the significance of SH groups in proteins?A. The SH group of cysteine can form a disulfide (SS) bond with another cysteineresidue. The two cysteine residues can connect two polypeptide chains by theformation of interchain disulfide bonds.Q. Glutathione is made up of which amino acids?A. Glutamic acid, cysteine and glycine.Q. Phosphorylation is taking place on which amino acid residue?A. SerineQ. What is ninhydrin reaction?A. All amino acids when heated with ninhydrin will give a pink colour.Q. What is the importance of ninhydrin reaction?A. It is used for qualitative test and quantitative estimation of amino acids. It is oftenused for detection of amino acids in chromatography. Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com
  • 6. Q. Do proteins give a color with ninhydrin?A. Proteins do not give a true color reaction; but N terminal end amino group ofprotein will react with ninhydrin, to produce a blue color.Q. What is biuret reaction?A. Cupric ions in alkaline medium form a violet colour with peptide bond nitrogen.Q. Will amino acids give a positive biuret test?A. No. This needs a minimum of two peptide bonds.Q. What is the use of biuret reaction?A. This reaction can be used for qualitative identification and quantitative estimationof proteins.Q. What is biuret?A. The name is derived from the compound biuret, a condensation product of twourea molecules, which also gives a positive color test.Q. What is the basis of xanthoproteic test?A. The ring systems in phenyl alanine, tyrosine and tryptophan will answer this test.Q. The protein which does not answer the aldehyde test is.A. Gelatin. Dr. Ehab Aboueladab, Associate Prof.Dr. Of Biochemistry and Nutrition, email:ehab10f@gmail.com

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