please answer following Problem #3 Amino acids are grouped according to the chem

Question

please answer following

Problem #3 Amino acids are grouped according to the chemical properties of their side chains (a) List all the 20 amino acids using both three-letter and one-letter abbreviations such as Asp (D), Glu (E), etc. and classify them into the following subgroups: cationic, anionic, neutral polar and hydrophobic amino acids. (b) What would be the most characteristic feature of hydrophobic side chains? (c) Which of the hydrophobic amino acids would you expect to exhibit the weakest hydrophobicity?

Explanation / Answer

A) Positively charged (cationic) amino acids:

Arg - R

Lys - K

His - H

Negatively charged (anionic) amino acids:

Asp - D

Glu - E

Neutral polar amino acids:

Gln - Q

Asn - N

Ser - S

Thr - T

Tyr - Y

Cys - C

Trp - W

Hydrophobic amino acids:

Ala - A

Ile - I

Leu - L

Met - M

Phe - F

Val - V

Pro - P

Gly - G

B) Hydrophobic means hydro – water, phobic – fearing. Hydrophobic amino acids have little or no polarity in their side chains. The lack of polarity means they have no way to interact with highly polar water molecules, making them water fearing. They can be categorised by the polar and non-polar hydrophobic according to their size of side chain. Small side chain shows weak hydrophobicity and large side chain shows strong hydrophobicity. These side chains are composed mostly of carbon and hydrogen, have very small dipole moments, and tend to be repelled from water.

C) Glycine is the weakest hydrophobic amino acids.

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