Help with Organic Proteins - Organic Chemistry
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Which of the following is an example of a basic amino acid?
Which of the following is an example of a basic amino acid?
Lysine's R-group includes an amine (-NH2), which can be ionized by picking up a hydrogen. This ability classifies lysine as basic.
Lysine's R-group includes an amine (-NH2), which can be ionized by picking up a hydrogen. This ability classifies lysine as basic.
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Which of the following amino acids can participate in the formation of a disulfide bridge?
Which of the following amino acids can participate in the formation of a disulfide bridge?
Cysteine's R-group contains a sulfhydryl group (-SH), which can participate in the formation of a disulfide bridge in a protein's tertiary and/or quaternary structure. Cysteine is the only amino acid to contain a sulfur atom.
Cysteine's R-group contains a sulfhydryl group (-SH), which can participate in the formation of a disulfide bridge in a protein's tertiary and/or quaternary structure. Cysteine is the only amino acid to contain a sulfur atom.
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How many essential amino acids are there?
How many essential amino acids are there?
The nine essential amino acids are valine, leucine, isoleucine, histidine, phenylalanine, tryptophan, methionine, threonine, and lysine. These amino acids must be consumed in the diet, since they cannot be synthesized by adult humans.
The nine essential amino acids are valine, leucine, isoleucine, histidine, phenylalanine, tryptophan, methionine, threonine, and lysine. These amino acids must be consumed in the diet, since they cannot be synthesized by adult humans.
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Which of the following amino acids is the only one to contain a side chain that results in an achiral amino acid?
Which of the following amino acids is the only one to contain a side chain that results in an achiral amino acid?
The only achiral amino acid is Glycene. Glycene's side chain is simply a hydrogen. Because a hydrogen already exists on the fundamental structure of an amino acid backbone, a side chain of a single hydrogen atom causes glycene to be achiral.
The only achiral amino acid is Glycene. Glycene's side chain is simply a hydrogen. Because a hydrogen already exists on the fundamental structure of an amino acid backbone, a side chain of a single hydrogen atom causes glycene to be achiral.
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What is the D/L configuration and the absolute (R/S) configuration of the following amino acid (cysteine)?
What is the D/L configuration and the absolute (R/S) configuration of the following amino acid (cysteine)?
Cysteine is an unusual amino acid. Although each of the normal biological amino acids have the L configuration (with the exception of glycine, which is achiral), meaning they can be drawn with the Fischer projection as shown:
the fact that cysteine contains a sulfur group makes the side chain a higher priority than the carboxylic acid. Therefore, the absolute configuration of cysteine will be R, and not S like the other amino acids.
Cysteine is an unusual amino acid. Although each of the normal biological amino acids have the L configuration (with the exception of glycine, which is achiral), meaning they can be drawn with the Fischer projection as shown:
the fact that cysteine contains a sulfur group makes the side chain a higher priority than the carboxylic acid. Therefore, the absolute configuration of cysteine will be R, and not S like the other amino acids.
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Consider L-glutamate, which is shown below.
Using the pKa information provided, what is the isoelectric point (pI) of the given molecule?
Consider L-glutamate, which is shown below.
Using the pKa information provided, what is the isoelectric point (pI) of the given molecule?
The isoelectric point is the average of the two pKa values around which the molecule has an overall neutral charge. In the case of glutamate, the amino acid is in its neutral (zwitterion) form in between the lower two pKa values. Taking the average of the two values gives the pI.
The isoelectric point is the average of the two pKa values around which the molecule has an overall neutral charge. In the case of glutamate, the amino acid is in its neutral (zwitterion) form in between the lower two pKa values. Taking the average of the two values gives the pI.
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Consider the amino acid L-lysine, shown below.
Given the pKa values shown, calculate the pI of lysine.
Consider the amino acid L-lysine, shown below.
Given the pKa values shown, calculate the pI of lysine.
The isoelectric point is the average of the two pKa values around which the molecule has an overall neutral charge. In the case of lysine, the amino acid is in its neutral (zwitterion) form in between the higher two pKa values. Taking the average of the two values gives the pI.
The isoelectric point is the average of the two pKa values around which the molecule has an overall neutral charge. In the case of lysine, the amino acid is in its neutral (zwitterion) form in between the higher two pKa values. Taking the average of the two values gives the pI.
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Treatment of a peptide with Edman's reagent yielded the following phenylthiohydantoin (PTH) derivative:
What is the side chain of the amino acid at the N-terminus of the peptide?
Treatment of a peptide with Edman's reagent yielded the following phenylthiohydantoin (PTH) derivative:
What is the side chain of the amino acid at the N-terminus of the peptide?
Treatment of a peptide with Edman's reagent (
) will remove the N-terminal amino acid. The PTH derivative will look as follows:
In the molecule in the question, a sec-butyl replaces the R group. This is the amino acid isoleucine.
Treatment of a peptide with Edman's reagent (
In the molecule in the question, a sec-butyl replaces the R group. This is the amino acid isoleucine.
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What is the amino acid that is synthesized from the malonic ester synthesis shown?
What is the amino acid that is synthesized from the malonic ester synthesis shown?
First step: Deprotonation of alpha hydrogen and formation of the malonic ester enolate.
Second step: bimolecular nucleophilic substitution, resulting in addition of the isopropyl group to the alpha carbon.
Third step: hydrolysis of amide and ester bonds, followed by decarboxylation
The synthesis forms valine, because the alkyl halide that is attacked is an isopropyl group (Valine's side chain is an isopropyl group). A more detailed mechanism is shown below.
First step: Deprotonation of alpha hydrogen and formation of the malonic ester enolate.
Second step: bimolecular nucleophilic substitution, resulting in addition of the isopropyl group to the alpha carbon.
Third step: hydrolysis of amide and ester bonds, followed by decarboxylation
The synthesis forms valine, because the alkyl halide that is attacked is an isopropyl group (Valine's side chain is an isopropyl group). A more detailed mechanism is shown below.
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