Amino Acids Net Charge and Zwitterions

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Which of the following statements about amino acids is correct?

Amino acids always have a zero net charge.

Amino acids can have a positive, negative, or zero net charge. (correct)

Amino acids can only have a positive or negative net charge.

Amino acids can only have a positive net charge.

What is the term used to describe an amino acid with an equal number of positively and negatively charged groups?

Neutral

Isoelectric

Zwitterion (correct)

Polar

What is the isoelectric pH (pI) for the amino acid aspartic acid?

pI = 9.2

pI = 5.0

pI = 7.4

pI = 3.9 (correct)

Which of the following statements about the solubility of amino acids is correct?

Amino acids with a positive or negative net charge are more soluble than those with a zero net charge. Signup and view all the answers

What is the primary structural feature that determines the properties of amino acids?

The side chain (R-group) Signup and view all the answers

What is the purpose of the non-α peptide bond in the structure of glutathione?

To link the glutamic acid and cysteine residues Signup and view all the answers

What is the primary function of amino acids in the body?

Structural components of proteins Signup and view all the answers

What is the charge on an amino acid at its isoelectric point (pI)?

Zero Signup and view all the answers

Which of the following best describes the zwitterionic nature of amino acids?

Amino acids have both positively and negatively charged groups Signup and view all the answers

Which type of amino acid has a non-polar, hydrophobic side chain?

Alanine Signup and view all the answers

What is the purpose of the R-group in amino acid structure?

To provide the amino acid with its unique chemical properties Signup and view all the answers

Which of the following best describes the peptide bond in a polypeptide chain?

It is a partial double bond with limited rotation Signup and view all the answers

What property of selenocysteine makes it a better nucleophile than cysteine at or below pH 7.4?

Selenocysteine has a lower pKa than cysteine, making it more reactive at physiological pH. Signup and view all the answers

Which of the following is an example of a nonprotein L-$\alpha$-amino acid?

$\beta$-Alanine Signup and view all the answers

What is the primary reason certain plant L-$\alpha$-amino acids can adversely impact human health?

They have structural modifications that make them toxic. Signup and view all the answers

What is the net charge of an amino acid at its isoelectric point?

Zero Signup and view all the answers

Which of the following is a characteristic of the zwitterionic form of an amino acid?

The carboxyl group is deprotonated and the amino group is protonated. Signup and view all the answers

What is the purpose of the resonance hybrids shown in Figure 3-4 for the R-groups of histidine and arginine?

To allow the R-groups to act as both acids and bases. Signup and view all the answers

Amino Acids Net Charge and Zwitterions

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