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Questions and Answers
Which type of amino acid has a chiral carbon?
Which type of amino acid has a chiral carbon?
Which amino acid does not have a chiral carbon?
Which amino acid does not have a chiral carbon?
At what pH does the COOH group of an amino acid get ionized into COO- and H+?
At what pH does the COOH group of an amino acid get ionized into COO- and H+?
At what pH does the amino group of an amino acid get deprotonated into NH2 and H+?
At what pH does the amino group of an amino acid get deprotonated into NH2 and H+?
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What is the net charge of COOH and NH2 groups in an amino acid at low pH?
What is the net charge of COOH and NH2 groups in an amino acid at low pH?
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Which species are present in an amino acid at high pH?
Which species are present in an amino acid at high pH?
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What is the pKa value for the COOH group of an amino acid?
What is the pKa value for the COOH group of an amino acid?
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At what pH is the NH3+ form of the amino group observed?
At what pH is the NH3+ form of the amino group observed?
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How many of the 20 amino acids have readily ionisable side chains?
How many of the 20 amino acids have readily ionisable side chains?
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Which type of bond gets formed between the carboxyl group of one amino acid and the amino group of the other amino acid?
Which type of bond gets formed between the carboxyl group of one amino acid and the amino group of the other amino acid?
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What is the primary structure of a protein?
What is the primary structure of a protein?
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Which amino acid is not found in alpha-helices due to its side chain that prevents it from forming hydrogen bonds?
Which amino acid is not found in alpha-helices due to its side chain that prevents it from forming hydrogen bonds?
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What stabilizes the tertiary structure of proteins?
What stabilizes the tertiary structure of proteins?
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What is the simplest form of quaternary structure in proteins?
What is the simplest form of quaternary structure in proteins?
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Which element can be included in a protein's 3D structure as a prosthetic group?
Which element can be included in a protein's 3D structure as a prosthetic group?
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What can denature a protein and result in the loss of its function?
What can denature a protein and result in the loss of its function?
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What is the part of a polypeptide chain that folds independently into a compact structure?
What is the part of a polypeptide chain that folds independently into a compact structure?
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What type of bond can form between cysteines in different polypeptide chains?
What type of bond can form between cysteines in different polypeptide chains?
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What determines the function of a protein?
What determines the function of a protein?
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Proteins always fold into the lowest energy conformation
Proteins always fold into the lowest energy conformation
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The primary structure of a protein is the sequence of amino acids in the polypeptide chain, which is always the same for all proteins
The primary structure of a protein is the sequence of amino acids in the polypeptide chain, which is always the same for all proteins
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Cystine is the only amino acid with an SH group that can form disulphide bonds
Cystine is the only amino acid with an SH group that can form disulphide bonds
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The side chains of amino acids in beta-sheets stick out above and below the sheet
The side chains of amino acids in beta-sheets stick out above and below the sheet
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Renaturation of denatured proteins is always possible
Renaturation of denatured proteins is always possible
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Study Notes
Structure of Amino Acids
- A central carbon atom is bonded to an amino group, a carboxyl group, a hydrogen atom, and a R group (variable side chain)
- All amino acids except glycine have a chiral carbon, with 4 different chemical groups attached, allowing for L and D isomers
- Only L amino acids are found in proteins
Glycine
- Glycine is the only amino acid without a chiral carbon, due to having only 3 different groups attached
- The R group in glycine is a hydrogen atom
Amino Acid Properties
- Different amino acids can vary in size, shape, charge, polarity, and chemical reactivity
- Key features of amino acids to know include their size, polarity, and unique characteristics
Amino Acids in Solution
- Amino acids in solution tend to exist as zwitterions, with both COOH and NH2 groups ionized
- The nature of the species present depends on the pH
- At low pH, both COOH and NH3 get protonated, resulting in a net charge of +1
- At high pH, both COOH and NH3 get deprotonated, resulting in a net charge of -1
pKa and Ionisation State
- pKa is the pH at which the concentrations of protonated and unprotonated forms are equal
- The ionisation state of amino acids varies with pH
- pKa for COOH is around 2, with COOH present at pH below 2 and COO- present at pH above 2
- pKa for the amino group is between 9-10, with NH3+ present at pH below 9 and NH2 present at pH above 10
Ionisable Side Chains
- 7 of the 20 amino acids have readily ionisable side chains
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Description
Test your knowledge of amino acid structure and properties with this quiz. Learn about the central carbon, amino group, carboxyl group, chiral carbon, R group, isomers, and the unique properties of glycine. Explore the variations in different amino acids and their significance in proteins.
