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Questions and Answers
What is the term used to describe substances that can act as both acids and bases?
What is the term used to describe substances that can act as both acids and bases?
At what pH does an amino acid carry a +ve charge on the amino group and no charge on the COOH group?
At what pH does an amino acid carry a +ve charge on the amino group and no charge on the COOH group?
What is the term used to describe the pH at which an amino acid has a net electric charge of zero?
What is the term used to describe the pH at which an amino acid has a net electric charge of zero?
What is the reaction between the COOH group of an amino acid and ammonia (NH3)?
What is the reaction between the COOH group of an amino acid and ammonia (NH3)?
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What type of reaction occurs when an amino acid reacts with a base?
What type of reaction occurs when an amino acid reacts with a base?
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What is the term used to describe the ion that an amino acid exists as in solution?
What is the term used to describe the ion that an amino acid exists as in solution?
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What is the name of the amino acid that has an isoelectric point equal to the arithmetic mean of the two pKa values?
What is the name of the amino acid that has an isoelectric point equal to the arithmetic mean of the two pKa values?
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What type of reaction occurs when an amino acid undergoes decarboxylation?
What type of reaction occurs when an amino acid undergoes decarboxylation?
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What type of bond joins amino acid residues in proteins?
What type of bond joins amino acid residues in proteins?
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In addition to protein synthesis, what is another function of amino acids and their derivatives?
In addition to protein synthesis, what is another function of amino acids and their derivatives?
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What are short polymers of amino acids called?
What are short polymers of amino acids called?
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Which of the following types of proteins can be found in the human body?
Which of the following types of proteins can be found in the human body?
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What do proteins yield upon complete hydrolysis?
What do proteins yield upon complete hydrolysis?
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What is the nature of the side chain attached to an alpha carbon atom in amino acids (excluding proline)?
What is the nature of the side chain attached to an alpha carbon atom in amino acids (excluding proline)?
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At physiological pH, what happens to the amino group in amino acids?
At physiological pH, what happens to the amino group in amino acids?
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What property does a carbon atom exhibit if it is attached to four different groups?
What property does a carbon atom exhibit if it is attached to four different groups?
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Which amino acid does not have optical isomers?
Which amino acid does not have optical isomers?
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Which type of amino acids are proteins composed of?
Which type of amino acids are proteins composed of?
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What characteristic do the R groups of alanine, valine, leucine, and isoleucine share?
What characteristic do the R groups of alanine, valine, leucine, and isoleucine share?
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What makes proline unique among amino acids?
What makes proline unique among amino acids?
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Which sulfur-containing amino acid is mentioned?
Which sulfur-containing amino acid is mentioned?
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What type of interactions help cluster the side chains of alanine, valine, leucine, and isoleucine within proteins?
What type of interactions help cluster the side chains of alanine, valine, leucine, and isoleucine within proteins?
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Which amino acid has an R group that is simply a hydrogen atom?
Which amino acid has an R group that is simply a hydrogen atom?
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Why are the R groups of certain amino acids more soluble in water than nonpolar amino acids?
Why are the R groups of certain amino acids more soluble in water than nonpolar amino acids?
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What is formed when α-amino acids react with ninhydrin?
What is formed when α-amino acids react with ninhydrin?
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What is the process called when an amino group is transferred from an amino acid to a keto acid?
What is the process called when an amino group is transferred from an amino acid to a keto acid?
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What happens during oxidative deamination?
What happens during oxidative deamination?
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Which amino acids are present in collagen, the most abundant protein in mammals?
Which amino acids are present in collagen, the most abundant protein in mammals?
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Which amino acid found in histones can undergo modifications such as methylation, phosphorylation, or acetylation?
Which amino acid found in histones can undergo modifications such as methylation, phosphorylation, or acetylation?
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Which plasma protein is involved in blood clotting and contains γ-carboxyglutamic acid?
Which plasma protein is involved in blood clotting and contains γ-carboxyglutamic acid?
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Which type of amino acids is the majority isolated from animals and plants?
Which type of amino acids is the majority isolated from animals and plants?
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Which amino acids are specifically found in certain antibiotics like actinomycin-D?
Which amino acids are specifically found in certain antibiotics like actinomycin-D?
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Which amino acids are exclusively ketogenic?
Which amino acids are exclusively ketogenic?
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Which amino acids are both ketogenic and glucogenic?
Which amino acids are both ketogenic and glucogenic?
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What makes selenocysteine unique among amino acids?
What makes selenocysteine unique among amino acids?
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How is pyrrolysine chemically characterized?
How is pyrrolysine chemically characterized?
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At what codon is selenocysteine incorporated during protein translation?
At what codon is selenocysteine incorporated during protein translation?
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Which characteristic is common to most amino acids?
Which characteristic is common to most amino acids?
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Which amino acid is typically tasteless?
Which amino acid is typically tasteless?
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Which property is common to all amino acids except glycine?
Which property is common to all amino acids except glycine?
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Study Notes
Amphoteric Substances
- Amphoteric describes substances that can act as both acids and bases.
Amino Acid Charge and pH
- The amino group carries a positive charge (+) and the COOH group has no charge at a pH below the pKa of the COOH group.
Isoelectric Point
- The isoelectric point (pI) is the pH at which an amino acid has a net electric charge of zero.
Amino Acid Reactions
- Reaction with ammonia (NH3): The COOH group of an amino acid reacts with ammonia to form an amide and water.
- Reaction with a base: The COOH group of an amino acid loses a proton (H+) to form a carboxylate ion (COO-) and water.
Ion Form of Amino Acids
- In solution, amino acids exist as zwitterions, which have both a positive and a negative charge.
Isoelectric Point and pKa
- The amino acid with an isoelectric point equal to the arithmetic mean of the two pKa values is glycine.
Decarboxylation
- Decarboxylation is the removal of a carboxyl group (COOH) from an amino acid, resulting in the formation of an amine and carbon dioxide (CO2).
Peptide bonds
- Peptide bonds link amino acid residues together in proteins through a condensation reaction between the carboxyl group of one amino acid and the amino group of another.
Functions of Amino Acids
- In addition to protein synthesis, amino acids and their derivatives are involved in various functions, including:
- Neurotransmitters: Some amino acids act as neurotransmitters in the nervous system, such as glutamate and GABA.
- Hormones: Certain amino acids are precursors to hormones, like tyrosine, a precursor to dopamine, norepinephrine, and epinephrine.
Short Polymers of Amino Acids
- Short polymers of amino acids are called peptides.
Proteins in the Human Body
- Types of proteins found in the human body include:
- Enzymes: Catalyze biochemical reactions.
- Antibodies: Part of the immune system, recognizing and neutralizing foreign substances.
- Hormones: Act as chemical messengers to regulate various bodily functions.
- Structural proteins: Provide support and structure to cells and tissues.
Hydrolysis of Proteins
- Complete hydrolysis of proteins yields amino acids.
Amino Acid Side Chains
- The side chain attached to an alpha carbon atom in amino acids (excluding proline) is variable and defines the unique properties of each amino acid.
Amino Group at Physiological pH
- At physiological pH, the amino group in amino acids is protonated, carrying a positive charge (+).
Chiral Carbon
- A carbon atom attached to four different groups exhibits chirality, meaning it has a non-superimposable mirror image.
Amino Acid Without Optical Isomers
- The amino acid glycine does not have optical isomers because its alpha carbon is attached to two identical hydrogen atoms.
Proteins and Amino Acids
- Proteins are composed of L-amino acids, which have a specific configuration at the alpha carbon.
Hydrophobic Amino Acids
- Alanine, valine, leucine, and isoleucine share the characteristic of having hydrophobic R groups.
Proline's Uniqueness
- Proline is unique among amino acids because its R group is bonded to the amino group, forming a cyclic structure.
Sulfur-Containing Amino Acid
- Methionine is a sulfur-containing amino acid.
Hydrophobic Interactions
- Hydrophobic interactions help cluster the side chains of alanine, valine, leucine, and isoleucine within proteins, driving their association and exclusion of water molecules.
Glycine's R Group
- Glycine has an R group that is simply a hydrogen atom.
Water Solubility of Amino Acids
- The R groups of certain amino acids, like lysine, are more soluble in water than nonpolar amino acids due to their polar, charged nature.
Ninhydrin Reaction
- When α-amino acids react with ninhydrin, they form a purple-colored product, used for identifying and quantifying amino acids.
Transamination
- In transamination, an amino group is transferred from an amino acid to a keto acid, forming a new amino acid and a new keto acid.
Oxidative Deamination
- Oxidative deamination removes an amino group from an amino acid, producing ammonia (NH3) and a keto acid.
Collagen's Amino Acids
- Glycine, proline, and hydroxyproline are abundant in collagen, the most abundant protein in mammals.
Histone Modifications
- Lysine, found in histones, can undergo modifications such as methylation, phosphorylation, or acetylation, affecting gene expression.
Blood Clotting Protein
- Prothrombin, a plasma protein involved in blood clotting, contains γ-carboxyglutamic acid.
Majority Amino Acids
- L-amino acids are the majority isolated from animals and plants.
Antibiotics and Amino Acids
- D-amino acids are specifically found in certain antibiotics like actinomycin-D.
Ketogenic Amino Acids
- Leucine and lysine are exclusively ketogenic amino acids, meaning they can be converted to ketone bodies.
Glucogenic and Ketogenic Amino Acids
- Isoleucine, phenylalanine, tryptophan, and tyrosine are both ketogenic and glucogenic, meaning they can be converted to glucose and ketone bodies.
Selenocysteine
- Selenocysteine is unique among amino acids because it contains a selenol (-SeH) group instead of a thiol group.
Pyrrolysine
- Pyrrolysine is chemically characterized by its pyrrolysine side chain, which is different from the standard 20 amino acids.
Selenocysteine Incorporation
- Selenocysteine is incorporated during protein translation at the UGA codon, which typically signals termination.
Common Feature of Amino Acids
- Most amino acids are chiral due to the presence of a chiral carbon atom.
Tasteless Amino Acid
- Glycine is typically tasteless.
Common Property of All Amino Acids
- All amino acids except glycine have a chiral alpha carbon.
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Description
This quiz explores the role of amino acids in protein synthesis, their participation in cellular functions, and their derivatives.
