To determine which list contains only neutral polar amino acids, we first need to review the characteristics of neutral polar amino acids. Neutral polar amino acids possess side chains that can form hydrogen bonds but do not carry a charge at physiological pH (pH ~7). Common neutral polar amino acids are:
- Serine (Ser)
- Threonine (Thr)
- Asparagine (Asn)
- Glutamine (Gln)
- Cysteine (Cys)
- Tyrosine (Tyr)
Now, let's analyze each provided list to identify which one contains only neutral polar amino acids:
A) Ser, Cys, Phe, Glu
- Serine (Ser) - Neutral polar amino acid
- Cysteine (Cys) - Neutral polar amino acid
- Phenylalanine (Phe) - Non-polar amino acid
- Glutamic acid (Glu) - Negatively charged (acidic) amino acid
- Conclusion: This list contains phenylalanine and glutamic acid, which are not neutral polar amino acids.
B) Asn, Gln, Cys, Tyr
- Asparagine (Asn) - Neutral polar amino acid
- Glutamine (Gln) - Neutral polar amino acid
- Cysteine (Cys) - Neutral polar amino acid
- Tyrosine (Tyr) - Neutral polar amino acid
- Conclusion: This list contains only neutral polar amino acids.
C) Lys, Glu, Thr, Tyr
- Lysine (Lys) - Positively charged (basic) amino acid
- Glutamic acid (Glu) - Negatively charged (acidic) amino acid
- Threonine (Thr) - Neutral polar amino acid
- Tyrosine (Tyr) - Neutral polar amino acid
- Conclusion: This list contains lysine and glutamic acid, which are not neutral polar amino acids.
D) Cys, Asn, His, Arg
- Cysteine (Cys) - Neutral polar amino acid
- Asparagine (Asn) - Neutral polar amino acid
- Histidine (His) - Positively charged (basic) amino acid
- Arginine (Arg) - Positively charged (basic) amino acid
- Conclusion: This list contains histidine and arginine, which are not neutral polar amino acids.
Based on the analysis, the list that contains only neutral polar amino acids is:
B) Asn, Gln, Cys, Tyr
