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Questions and Answers
Which group is responsible for the formation of a peptide bond?
Which group is responsible for the formation of a peptide bond?
What happens to the carboxyl group at physiological pH?
What happens to the carboxyl group at physiological pH?
Which of the following statements correctly describes a zwitter ion?
Which of the following statements correctly describes a zwitter ion?
Which classification of amino acids is characterized by a single carboxyl group and a single amino group?
Which classification of amino acids is characterized by a single carboxyl group and a single amino group?
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What distinguishes proline from the other amino acids?
What distinguishes proline from the other amino acids?
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Which of the following amino acids is classified as basic due to its side chain containing an NH2 group?
Which of the following amino acids is classified as basic due to its side chain containing an NH2 group?
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What is a common characteristic of acidic amino acids at physiological pH?
What is a common characteristic of acidic amino acids at physiological pH?
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Which amino acid contains a guanido group in its structure?
Which amino acid contains a guanido group in its structure?
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Which amino acid is considered a neutral amino acid due to its side chain being amidated?
Which amino acid is considered a neutral amino acid due to its side chain being amidated?
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What is the R group for Glycine?
What is the R group for Glycine?
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What functional groups are primarily associated with polar amino acids?
What functional groups are primarily associated with polar amino acids?
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Which amino acid has an isopropyl group as its R group?
Which amino acid has an isopropyl group as its R group?
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Which of the following amino acids falls into the category of non-polar amino acids?
Which of the following amino acids falls into the category of non-polar amino acids?
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What distinguishes Serine from Threonine in their structures?
What distinguishes Serine from Threonine in their structures?
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Which amino acid is characterized by a sulfur atom in its structure?
Which amino acid is characterized by a sulfur atom in its structure?
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Which amino acid is an example of a basic heterocyclic amino acid?
Which amino acid is an example of a basic heterocyclic amino acid?
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What is the primary charge of aspartic acid at physiological pH?
What is the primary charge of aspartic acid at physiological pH?
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Which of the following amino acids is branched chain?
Which of the following amino acids is branched chain?
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What is the primary function of the phenyl group in Phenylalanine?
What is the primary function of the phenyl group in Phenylalanine?
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Which amino acid has the structure HO-C-C-N with a hydroxyl group in its R group?
Which amino acid has the structure HO-C-C-N with a hydroxyl group in its R group?
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Which of the following statements about the neutral hydroxy amino acids is true?
Which of the following statements about the neutral hydroxy amino acids is true?
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Which of the following amino acids is classified as non-polar?
Which of the following amino acids is classified as non-polar?
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Which amino acid is essential and cannot be synthesized by the body?
Which amino acid is essential and cannot be synthesized by the body?
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What distinguishes polar amino acids from non-polar amino acids?
What distinguishes polar amino acids from non-polar amino acids?
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Which of the following amino acids contains sulfur in its structure?
Which of the following amino acids contains sulfur in its structure?
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Which amino acid is considered to be the most hydrophobic?
Which amino acid is considered to be the most hydrophobic?
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In which category does methionine fall?
In which category does methionine fall?
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Which amino acid has a side chain that contributes to protein structure through disulfide bonds?
Which amino acid has a side chain that contributes to protein structure through disulfide bonds?
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Which of the following amino acids is non-polar and branched?
Which of the following amino acids is non-polar and branched?
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Lysine is often characterized as which type of amino acid?
Lysine is often characterized as which type of amino acid?
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Which amino acid is noted for having an aliphatic side chain?
Which amino acid is noted for having an aliphatic side chain?
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Which amino acids are classified as essential amino acids?
Which amino acids are classified as essential amino acids?
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What characterizes semiessential amino acids?
What characterizes semiessential amino acids?
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Which group does not include ketogenic amino acids?
Which group does not include ketogenic amino acids?
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What type of amino acids yield both ketone bodies and glucose?
What type of amino acids yield both ketone bodies and glucose?
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What property of amino acids allows them to act as both acids and bases?
What property of amino acids allows them to act as both acids and bases?
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How is a peptide bond formed between two amino acids?
How is a peptide bond formed between two amino acids?
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Which of the following statements about peptide chains is correct?
Which of the following statements about peptide chains is correct?
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What is the significance of the isoelectric point (IEP) for amino acids?
What is the significance of the isoelectric point (IEP) for amino acids?
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What type of bond connects amino acids in a dipeptide?
What type of bond connects amino acids in a dipeptide?
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Which term describes the end of a polypeptide chain that has a free amino group?
Which term describes the end of a polypeptide chain that has a free amino group?
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What do all proteins share in common regarding their amino acid components?
What do all proteins share in common regarding their amino acid components?
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Which group of amino acids is likely to possess a net negative charge at physiological pH?
Which group of amino acids is likely to possess a net negative charge at physiological pH?
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Which amino acid is considered optically inactive due to its structure?
Which amino acid is considered optically inactive due to its structure?
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What type of amino acids are predominantly found as dipolar ions at neutral pH?
What type of amino acids are predominantly found as dipolar ions at neutral pH?
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Which amino acid is an example of a sulfur-containing amino acid?
Which amino acid is an example of a sulfur-containing amino acid?
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At which end of a polypeptide chain does protein synthesis begin?
At which end of a polypeptide chain does protein synthesis begin?
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Study Notes
Amino Acids
- Amino acids are the building blocks of proteins
- There are about 300 amino acids found in nature, but only 20 are used in proteins
- Each amino acid has four different groups attached to its central carbon atom. These groups are: an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group). The side chain is specific to each amino acid.
Classification of Amino Acids
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Chemical Classification: Based on the number of carboxyl and amino groups, amino acids are classified as neutral and charged.
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Neutral: Monobasic, monocarboxylic (neutral or uncharged). These can be
- Simple: Glycine, Alanine.
- Branched Chain: Valine, Leucine, Isoleucine.
- Sulfur containing: Cysteine, Methionine.
- Hydroxy: Serine, Threonine.
- Aromatic: Phenylalanine, Tyrosine, Tryptophan.
- Heterocyclic: Proline.
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Charged: These can have either a positive or negative charge.
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Basic: Lysine, Arginine, Histidine.
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Acidic: Aspartate, Glutamate.
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- Essential Amino Acids: These cannot be synthesized by the body and must be obtained from the diet. Examples: Valine, Leucine, Isoleucine, Threonine, Methionine, Lysine, Phenylalanine, Tryptophan.
- Semi-Essential Amino Acids: Can be synthesized by the body but in insufficient amounts for certain age groups, especially children. Examples are Histidine, Arginine).
- Non-Essential Amino acids: The remaining amino acids that the body synthesizes in sufficient amount for adults and children.
Metabolic Classification
- Ketogenic Amino Acids: These yield ketone bodies during metabolism. Examples: Lysine, Leucine.
- Mixed Ketogenic and Glucogenic Amino Acids: These yield both ketone bodies and glucose, e.g., Isoleucine, Phenylalanine, Tyrosine, Tryptophan.
- Glucogenic Amino Acids: These yield glucose during metabolism, representing the remainder of the amino acids.
Properties
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Amphoteric: Amino acids are amphoteric molecules, meaning they exhibit both acidic and basic properties.
- At physiological pH, neutral amino acids exist as zwitterions (molecules bearing both positive and negative charges).
- Isoelectric point (IEP) is the pH at which the zwitterion has a net zero charge.
- Physical Properties: Includes the ability to form hydrogen bonds with water, polarity, and hydrophobic/hydrophilic characteristics.
- Chemical Properties: The reactions based on the carboxyl group, the reactions based on the amino group, reactions based on the side chain (R) group, and peptide bond formation.
Peptides and Proteins
- Peptides and proteins are formed from linked amino acids through peptide bonds.
- Short chains (less than 50 amino acids) are called peptides.
- Long chains (more than 50 amino acids) are called proteins.
- A peptide bond forms between the carboxyl group of one amino acid and the amino group of another, releasing a water molecule.
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Description
Explore the fascinating world of amino acids, which serve as the building blocks of proteins. This quiz covers the different types of amino acids, including their chemical classification into neutral and charged categories. Test your knowledge on specific amino acids and their unique properties.
