18 Questions
Glycine is an asymmetric center
False
D-amino acids are found in proteins
False
Histamine is an α-amino acid
False
NH2 group is always attached to the α-carbon atom in amino acids
False
Taurine is a constituent of vitamin B5
False
Citrulline is a standard amino acid
False
Glycine is a branched chain amino acid.
False
Amino acids with amide groups include Aspartic acid and Glutamic acid.
False
Phenylalanine is a heterocyclic amino acid.
False
Non-polar amino acids are generally found on the surface of proteins that interact with lipids.
False
Cysteine residues can form a peptide bond.
False
Charged side chains include Asparagine and Glutamine.
False
All amino acids have a planar structure.
False
There are 30 amino acids that occur in proteins.
False
The side chain (R-group) of an amino acid determines its metabolic fate.
True
Amino acids are linked to each other through ionic bonds.
False
The body can synthesize all amino acids.
False
Each amino acid has a unique one-letter symbol.
True
Study Notes
Classification of Amino Acids
- Aliphatic amino acids: Monoamino monocarboxylic acids (Simple amino acids: Glycine, Alanine), Branched chain amino acids (Valine, Leucine, Isoleucine), Hydroxy-amino acids (Serine, Threonine), Sulfur-containing amino acids (Cysteine, Methionine), Amino acids with amide group (Asparagine, Glutamine)
Acidic and Basic Amino Acids
- Monoamino dicarboxylic acids: Aspartic acid, Glutamic acid (acidic)
- Dibasic monocarboxylic acids: Lysine, Arginine (basic)
Aromatic and Heterocyclic Amino Acids
- Aromatic amino acids: Phenylalanine, Tyrosine
- Heterocyclic amino acids: Tryptophan, Histidine
Side Chain Character
- Non-polar side chains (hydrophobic): Ala, Val, Leu, Ile, Met, Phe, Try, Pro
- Polar side chains (hydrophilic): Ser, Thr, Tyr, Asn, Gln, Cys
- Charged side chains: Acidic (Glu, Asp), Basic (Lys, Arg, His)
Bonds and Interactions
- Non-polar amino acids participate in hydrophobic interactions
- Polar amino acids form hydrogen bonds
- Negatively charged acidic amino acids and positively charged basic amino acids form ionic bonds at physiological pH
- Two cysteine residues form a disulfide bond, producing cystine
Location of Polar and Non-Polar Amino Acids
- Non-polar amino acids are generally found in the interior of proteins that function in an aqueous environment
- Polar amino acids are generally found on the outside of proteins that function in an aqueous environment
Non-Standard Amino Acids
- γ-Amino butyric acid (GABA) derived from glutamic acid
- Beta alanine is a constituent of pantothenic acid (vitamin B5)
- Dopamine, Thyroxine (tyrosine derivative), Histamine (histidine derivative)
- Ornithine, Citrulline, Homocysteine are produced during the metabolism of amino acids
Importance of Amino Acids
- Formation of protein
- Formation of glucose and ketone bodies
- Enzyme activity: cysteine (-SH)
- Transport and storage form of ammonia: Gln
- As a buffer: histidine
- Detoxification: Gly, Cys
- Used as a drug: D-Penicillamine (D-dimethylglycine) for Wilson's disease
Test your knowledge of the different types of amino acids, including aliphatic, branched chain, hydroxy-amino, and more. Identify the characteristics and examples of each amino acid group.
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