Amino Acids & Proteins QuestionsQ1a Define ‘essential amino acids’b Define ‘nonessential amino acids’c What happens if you are deficient in an essential amino acidQ2Draw the functional groups present

Q1 a. Essential amino acids are amino acids that cannot be synthesized by the body and must be obtained through dietary sources. b. Nonessential amino acids are amino acids that the body can synthesize on its own and do not need to be obtained through dietary sources. c. If you are deficient in an essential amino acid, it can lead to impaired growth, muscle wasting, and various other health problems.

Q2 The functional groups present in all amino acids are:

• Amino group (-NH2)
• Carboxyl group (-COOH)
• Side chain or R group

Q3 a. Threonine:

• Amino acid structure: CH3-CH(OH)-CH(NH2)-COOH b. Circle the side chain: The side chain of threonine is CH(OH)-CH3 c. Threonine is polar. d. Threonine will exist as a zwitterion at a pH of around 2.8. e. Threonine will be positively charged at pH values below 2.8. f. Threonine will be negatively charged at pH values above 2.8.

a. Lysine:

• Amino acid structure: NH2-(CH2)4-CH(NH2)-COOH b. Circle the side chain: The side chain of lysine is (CH2)4-CH(NH2)-COOH c. Lysine is basic. d. Lysine will exist as a zwitterion at a pH of around 9.8. e. Lysine will be positively charged at pH values below 9.8. f. Lysine will not be negatively charged in the physiological pH range.

a. Tyrosine:

• Amino acid structure: HO-Ph-CH2-CH(NH2)-COOH b. Circle the side chain: The side chain of tyrosine is Ph-CH2-CH(NH2)-COOH (Ph represents a phenyl group) c. Tyrosine is polar. d. Tyrosine will exist as a zwitterion at a pH of around 5.6. e. Tyrosine will be positively charged at pH values below 5.6. f. Tyrosine will be negatively charged at pH values above 5.6.

Q4 a. Tyrosine and lysine can form the dipeptides tyrosine-lysine and lysine-tyrosine. b. Threonine and glutamine can form the dipeptides threonine-glutamine and glutamine-threonine. c. Alanine and histidine can form the dipeptides alanine-histidine and histidine-alanine.