Concept explainers
(a)
Interpretation: To identify whether the statement “four of the 20 standard amino acids contain sulfur” concerning sulfur-containing amino acids is true or false.
Concept introduction: Amino acids are the
There are 20 amino acids present in nature. These are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, asparagines, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
(b)
Interpretation: To identify whether the statement “the first step in the degradation of the amino acid cysteine is a transamination reaction” concerning sulfur-containing amino acids is true or false.
Concept introduction: There are 20 amino acids present in nature. These are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, asparagines, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. Only two of the twenty amino acids have a sulfur atom in their structure. The two amino acids are cysteine and methionine. The structure of cysteine is:
Cysteine gives pyruvate as the degradation product. The degradation of cysteine is a two-step process.
(c)
Interpretation: To identify whether the statement “pyruvate is the sulfur-containing product from the degradation of the amino acid cysteine” concerning sulfur-containing amino acids is true or false.
Concept introduction: There are 20 amino acids present in nature. These are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, asparagines, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine. Only two of the twenty amino acids have a sulfur atom in their structure. The two amino acids are cysteine and methionine. The structure of cysteine is:
Cysteine gives pyruvate as the degradation product. The degradation of cysteine is a two-step process.
(d)
Interpretation: To identify whether the statement “ATP is the activating agent in the first step of the conversion of serine to cysteine” concerning sulfur-containing amino acids is true or false.
Concept introduction: There are 20 amino acids present in nature. Only two of the twenty amino acids have a sulfur atom in their structure. Cysteine is biosynthesized from nonessential amino acid serine. The structure of cysteine is:
The structure of serine is:
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General, Organic, and Biological Chemistry
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