Which amino acid is ideal for the transfer of protons within the catalytic site of enzymes due to the presence of significant amounts of both the protonated and deprotonated forms of its side chain at biological pH?

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#Question id: 161

#Unit 1. Structure and Function of Biomolecules

Two amino acids of the standard 20 contain sulfur atoms.  They are:

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#Question id: 162

#Unit 1. Structure and Function of Biomolecules

All of the amino acids that are found in proteins, except for proline, contain a(n):

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#Question id: 163

#Unit 1. Structure and Function of Biomolecules

Which of the following statements about cystine is correct?

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#Question id: 164

#Unit 1. Structure and Function of Biomolecules

The uncommon amino acid selenocysteine has an R group with the structure —CH2—SeH (pKa = 5).  In an aqueous solution, pH = 7.0, selenocysteine would:

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#Question id: 165

#Unit 1. Structure and Function of Biomolecules

Amino acids are ampholytes because they can function as either a(n):

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#Question id: 166

#Unit 1. Structure and Function of Biomolecules

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have: