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Questions and Answers
What do peptides serve as precursors of?
What do peptides serve as precursors of?
Which amino acid protects living organisms against free radical induced damage?
Which amino acid protects living organisms against free radical induced damage?
What biological functions do peptides have?
What biological functions do peptides have?
Which of the following is NOT mentioned as a biological function of peptides?
Which of the following is NOT mentioned as a biological function of peptides?
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Peptides are involved in which of the following processes?
Peptides are involved in which of the following processes?
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What is a common use of peptides?
What is a common use of peptides?
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What are the three main components that make up an amino acid?
What are the three main components that make up an amino acid?
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What is the function of the α-carbon in an amino acid?
What is the function of the α-carbon in an amino acid?
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Which category of amino acids includes Valine, Leucine, and Lysine?
Which category of amino acids includes Valine, Leucine, and Lysine?
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Which type of amino acids can be synthesized in the body but may not meet the body's requirements during growth or pregnancy?
Which type of amino acids can be synthesized in the body but may not meet the body's requirements during growth or pregnancy?
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What happens if essential amino acids are absent in the diet?
What happens if essential amino acids are absent in the diet?
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How do non-essential amino acids differ from essential amino acids?
How do non-essential amino acids differ from essential amino acids?
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What is the term used to describe molecules that exist in two optically active asymmetric forms?
What is the term used to describe molecules that exist in two optically active asymmetric forms?
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At what pH does the basic amino group in free amino acids typically have a pKa value?
At what pH does the basic amino group in free amino acids typically have a pKa value?
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What is the term used for compounds like amino acids that can act as both an acid and a base?
What is the term used for compounds like amino acids that can act as both an acid and a base?
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Why is it essential to note that amino acids found in proteins almost always possess only the l-configuration?
Why is it essential to note that amino acids found in proteins almost always possess only the l-configuration?
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When do free amino acids exist largely as dipolar ions or zwitterions?
When do free amino acids exist largely as dipolar ions or zwitterions?
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What is the significance of the isoelectric point of zwitterions?
What is the significance of the isoelectric point of zwitterions?
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Study Notes
Structure and Classification of Amino Acids
- Amino acids are organic molecules consisting of a basic amino group (―NH2), an acidic carboxyl group (―COOH), and an organic R group (or side chain) that is unique to each amino acid
- The term amino acid is short for α-amino [alpha-amino] carboxylic acid
- Each molecule contains a central carbon (C) atom, called the α-carbon, to which both an amino and a carboxyl group are attached
Classification of Amino Acids
- Essential amino acids: cannot be synthesized in the body and must be present in the diet (e.g., Valine, Isoleucine, Leucine, Lysine, Methionine, Threonine, Tryptophan, and Phenylalanine)
- Semi-essential amino acids: can be synthesized in the body, but the rate of synthesis is lesser than the requirement (e.g., Arginine and Histidine)
- Non-essential amino acids: synthesized in the body, and their absence in the diet does not affect growth (e.g., Glycine, Alanine, and other remaining amino acids)
Chirality
- All amino acids except glycine are chiral molecules, existing in two optically active asymmetric forms (enantiomers) that are mirror images of each other
- Amino acids found in proteins almost always possess only the L-configuration
Acid-Base Properties
- Amino acids have both a basic and an acidic group at the α-carbon, making them amphoteric
- Basic amino group has a pKa between 9 and 10, while the acidic α-carboxyl group has a pKa close to 2
- At physiological pH (about 7–7.4), free amino acids exist largely as dipolar ions or “zwitterions”
Biological Role of Amino Acids
- Amino acids serve as building blocks of proteins
- Some amino acids are found in free form in human blood
- Peptides have many important biological functions, including:
- Hormones
- Antibiotics and antitumor agents
- Detoxification reactions
- Neurotransmitters
- Regulation of cell cycle and apoptosis
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Description
Explore the various biological functions of peptides, including their role as precursors of hormones, vitamins, and neurotransmitters. Learn about peptides' significance in detoxification reactions, regulation of cell functions, and protection against free radical damage.
