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How many amino acids have been found in nature that are directly involved in the structure of body proteins?
What is the function of L α-amino acids in the context of protein synthesis?
What distinguishes D-amino acids from L-amino acids in biological systems?
What are amino acids primarily considered in the context of proteins?
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Which of the following is NOT a recognized function of amino acids?
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What is meant by the term 'amphoteric properties' in relation to amino acids?
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Which of the following groups best represents the nutritional classification of amino acids?
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In the context of the general structure of amino acids, what does R represent in the amino acid structure?
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Which amino acid is classified as nonessential and can be synthesized by the human body?
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Which amino acid contains an indole ring structure?
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What is the primary reason essential amino acids are vital for human health?
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Which of the following amino acids is considered ketogenic?
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Which of these proteins is considered to have a high biological value?
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What classification applies to amino acids that can give rise to glucose?
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Which of the following amino acids is not classified as a heterocyclic amino acid?
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Which amino acid is known to contain a pyrrolidine ring structure?
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Which of the following amino acids belongs to the aliphatic category?
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Identify the amino acid that contains a sulfur atom.
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Which of the following amino acids is classified as a basic amino acid?
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Which amino acid listed is an aromatic amino acid containing a benzene ring?
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What is the structure type of aspartic acid?
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Which of the following is NOT a characteristic of branched-chain amino acids?
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What type of amino acid is proline categorized under?
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Which amino acid is primarily known for its role in the formation of disulfide bonds?
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Which amino acids are exclusively ketogenic?
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Which of the following amino acids can be classified as both glucogenic and ketogenic?
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At the isoelectric point, the amino group of an amino acid gains which type of charge?
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Which property allows amino acids to act as both acids and bases?
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What is the ion form called when an amino acid is at its isoelectric point?
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Which of the following is NOT a glucogenic amino acid?
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Which amino acids are primarily glucogenic?
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What occurs to the carboxyl group of an amino acid at its isoelectric point?
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Study Notes
Introduction
- There are hundreds of amino acids in nature.
- 20 amino acids are essential for the structure of the human body.
- These 20 amino acids have genetic codes on DNA.
Structure
- An amino acid is an organic acid, where one hydrogen atom is replaced by an amino group (NH2).
- The amino group is attached to the α-carbon atom.
Isomerism
- Most amino acids can exist in two optical isomers: D or L.
- Only L α-amino acids are used in the formation of body proteins.
- D-amino acids are found in some organisms and plants.
Functions
- Amino acids are the basic building blocks of proteins.
- They are a source of energy.
- They are used to synthesize other molecules, for example, Glycine forms 33% of collagen protein.
Classification by Structure
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Aliphatic amino acids have no ring structure.
- Neutral: Glycine, Alanine.
- Branched chain: Valine, Leucine, Isoleucine.
- Hydroxy-containing: Serine, Threonine, Tyrosine.
- Sulfur-containing: Cysteine, Methionine.
- Acidic: Aspartic acid, Glutamic acid.
- Basic: Arginine, Lysine.
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Aromatic amino acids contain an aromatic ring.
- Phenylalanine.
- Tyrosine.
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Heterocyclic amino acids have a ring structure containing atoms other than carbons.
- Tryptophan.
- Histidine.
- Proline.
Nutritional Classification
- Essential amino acids cannot be synthesized by the human body and must be obtained from food.
- Nonessential amino acids can be synthesized by the body.
- Proteins containing all essential amino acids are of high biological value.
- Proteins deficient in one or more essential amino acids are of low biological value.
Metabolic Fate
- Glucogenic amino acids can be converted to glucose.
- Ketogenic amino acids can be converted to ketone bodies.
- Glucogenic and ketogenic amino acids can be converted to both glucose and ketone bodies.
- Leucine and lysine are the only ketogenic amino acids.
- Isoleucine, tryptophan, tyrosine, and phenylalanine are the only glucogenic and ketogenic amino acids.
- The rest are glucogenic.
Amphoteric Properties
- Amino acids are amphoteric, meaning they can act as both acids and bases.
- The isoelectric point is the pH at which the amino acid has a net charge of zero.
- At the isoelectric point, the amino group gains a positive charge (is protonated) and the acid group gains a negative charge (is deprotonated).
- This ion is called a zwitterion.
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Description
This quiz covers the structure, classification, and functions of amino acids, focusing on their role in the human body. It includes details about essential amino acids, isomerism, and their significance in protein synthesis and energy production.
