Amino Acids with Ionizable Side Chains

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Questions and Answers

What are the 7 amino acids with ionizable side chains?

lysine, aspartic acid, cysteine, tyrosine, arginine, glutamic acid, histidine

What is the pKa of the lysine side chain?

10.5

What is the pKa of the aspartic acid side chain?

3.9

What is the pKa of the cysteine side chain?

8.4 Signup and view all the answers

What is the pKa of the tyrosine side chain?

10.5 Signup and view all the answers

What is the pKa of the arginine side chain?

12.5 Signup and view all the answers

What is the pKa of the glutamic acid side chain?

4.1 Signup and view all the answers

What is the pKa of the histidine side chain?

6.0 Signup and view all the answers

What are the 9 nonpolar amino acids?

glycine, alanine, valine, leucine, isoleucine, methionine, tryptophan, phenylalanine, proline Signup and view all the answers

What are the 6 polar amino acids?

serine, threonine, cysteine, tyrosine, asparagine, glutamine Signup and view all the answers

What are the 5 charged amino acids?

aspartic acid, glutamic acid, lysine, arginine, histidine Signup and view all the answers

What is the R group of lysine?

-CH2-CH2-CH2-CH2-NH3+ Signup and view all the answers

What is the R group of aspartic acid?

-CH2-COO- Signup and view all the answers

What is the R group of cysteine?

-CH2-SH Signup and view all the answers

What is the R group of tyrosine?

-CH2-benzene ring-OH Signup and view all the answers

What is the R group of arginine?

-CH2-CH2-CH2-NH-C=NH2+-NH2 Signup and view all the answers

What is the R group of glutamic acid?

-CH2-CH2-COO- Signup and view all the answers

What is the R group of histidine?

-CH2-amide ring-NH+ Signup and view all the answers

Describe what an amino acid looks like in a vacuum.

alpha amine group deprotonated - NH2; alpha carboxylic group protonated - COOH Signup and view all the answers

Describe what an amino acid looks like in water.

alpha amine group protonated - NH3+; alpha carboxylic group deprotonated - COO- Signup and view all the answers

Study Notes

Ionizable Amino Acids

Seven amino acids have ionizable side chains: lysine, aspartic acid, cysteine, tyrosine, arginine, glutamic acid, and histidine.

pKa Values of Ionizable Side Chains

Lysine has a side chain pKa of 10.5.
Aspartic acid's side chain pKa is 3.9.
Cysteine's side chain pKa is 8.4.
Tyrosine exhibits a side chain pKa of 10.5.
Arginine has a side chain pKa of 12.5.
Glutamic acid's side chain pKa is 4.1.
Histidine shows a side chain pKa of 6.0.

Nonpolar Amino Acids

Nine nonpolar amino acids include: glycine, alanine, valine, leucine, isoleucine, methionine, tryptophan, phenylalanine, and proline.

Polar Amino Acids

Six polar amino acids are identified as: serine, threonine, cysteine, tyrosine, asparagine, and glutamine.

Charged Amino Acids

Five amino acids are classified as charged: aspartic acid (acidic), glutamic acid (acidic), lysine (basic), arginine (basic), and histidine (basic).

Side Chain Structures

Lysine's side chain: -CH2-CH2-CH2-CH2-NH3+.
Aspartic acid's side chain: -CH2-COO-.
Cysteine's side chain: -CH2-SH.
Tyrosine's side chain: -CH2-benzene ring-OH.
Arginine's side chain: -CH2-CH2-CH2-NH-C=NH2+-NH2.
Glutamic acid's side chain: -CH2-CH2-COO-.
Histidine's side chain: -CH2-amide ring-NH+.

Amino Acid in a Vacuum

In a vacuum, the alpha amine group is deprotonated (NH2), while the alpha carboxylic group is protonated (COOH).

Amino Acid in Water

When in water, the alpha amine group is protonated to form NH3+, and the alpha carboxylic group is deprotonated, resulting in COO-.

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Description

This quiz covers the seven amino acids that have ionizable side chains, including their names and pKa values. Test your knowledge on the characteristics and properties of these important amino acids essential for understanding biochemistry.