Essential vs. Non-essential Amino Acids Quiz
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Questions and Answers

Which amino acids are considered indispensable or essential because they cannot be synthesized in the human body in adequate amounts and must be supplied in the diet?

Val, Ile, Thr, Trp, Arg, Leu, Lys, Met, Phe, His

Which amino acids are considered dispensable or non-essential because they are synthesizable in the body and there is no diet dependency for them?

Glu, Gln, Asp, Asn, Gly, Ala, Pro, Tyr, Ser, Cys

What are the consequences of dietary deficiency or imbalance of any of the essential amino acids?

Nutrition deficiency disorders that affect both growth and health

Which amino acids are semi-essential, meaning that the healthy adult human body synthesizes just enough but such amount is not enough in certain conditions and requires dietary supplementation?

<p>Arg and His</p> Signup and view all the answers

In what conditions is the amount of Arg and His synthesized by the healthy adult human body not enough, requiring dietary supplementation?

<p>Childhood growth period, sickness, convalescence, and during pregnancy</p> Signup and view all the answers

In what conditions does tyrosine become an essential amino acid, and what is its dietary dependency?

<p>Tyrosine becomes essential upon dietary deficiency of phenylalanine.</p> Signup and view all the answers

Under what condition does cysteine become an essential amino acid, and what is its dietary dependency?

<p>Cysteine becomes essential upon dietary deficiency of methionine.</p> Signup and view all the answers

What are the main dietary sources of essential amino acids, and what is the characteristic of these proteins?

<p>The main dietary sources of essential amino acids are proteins of high biological value, which are digestible proteins containing all essential amino acids in well-balanced proportions. These proteins include animal proteins (e.g., milk, egg, meat, liver, fish, and chicken) and a few plant proteins (e.g., from beans and lentils).</p> Signup and view all the answers

Which amino acids become essential under certain dietary deficiencies and what are their respective dietary dependencies?

<p>Tyrosine becomes essential upon dietary deficiency of phenylalanine, while cysteine becomes essential upon dietary deficiency of methionine.</p> Signup and view all the answers

What are the main dietary sources of essential amino acids and what is the characteristic of these proteins?

<p>The main dietary sources of essential amino acids are proteins of high biological value, which include all animal proteins (e.g., milk, egg, meat, liver, fish and chicken) and a few plant proteins (e.g. from beans and lentils). These proteins are digestible and contain all essential amino acids in well-balanced proportions.</p> Signup and view all the answers

Why are the remaining non-essential amino acids considered diet independent, and what is their metabolic significance?

<p>The remaining non-essential amino acids are considered diet independent because they are synthesized in the body. Despite being diet independent, these non-essential amino acids are metabolically as important as the essential ones.</p> Signup and view all the answers

Which amino acids are classified as glucogenic and why?

<p>14 of the 20 protein AAs are classified as glucogenic because they give rise to intermediates of glycolysis or Kreb’s cycle and can be converted to carbohydrates.</p> Signup and view all the answers

What distinguishes the ketogenic amino acids lysine and leucine from others?

<p>Lysine and leucine are purely ketogenic as they catabolically give intermediates convertible into acetyl-CoA or acetoacetyl-CoA.</p> Signup and view all the answers

What are mixed amino acids and how are they metabolized?

<p>Mixed amino acids have C skeletons that are catabolized to produce glycolytic intermediates as well as acetyl-CoA derivatives.</p> Signup and view all the answers

What are some examples of unusual amino acids formed after modification, and how are they created?

<p>Unusual amino acids, such as hydroxyl-proline, hydroxyl-lysine, and γ-carboxy glutamic acid, are formed after incorporation into proteins and modification by hydroxylation, methylation, or carboxylation.</p> Signup and view all the answers

What is selenocysteine (Sec) and how is it involved in protein structure and function?

<p>Selenocysteine is an amino acid present at the active site of several enzymes, such as gluthathione peroxidase, and is associated with antioxidant activity. It is formed during translation, and a special tRNA specific for ‘UGA’ (STOP) codon is used.</p> Signup and view all the answers

Which type of amino acids can be converted to carbohydrates and are known as glucogenic?

<p>Amino acids that give rise to glycolytic intermediates</p> Signup and view all the answers

Which two amino acids are purely ketogenic and give intermediates convertible into acetyl-CoA or acetoacetyl-CoA?

<p>Lysine and leucine</p> Signup and view all the answers

What are amino acids called that produce glycolytic intermediates as well as acetyl -CoA derivatives?

<p>Mixed amino acids</p> Signup and view all the answers

What is the 21st amino acid of proteins, which is present at the active site of several enzymes and is associated with antioxidant activity?

<p>Selenocysteine (Sec)</p> Signup and view all the answers

What is formed during translation, and has a special tRNA specific for ‘UGA’ (STOP) codon?

<p>Selenocysteine (Sec)</p> Signup and view all the answers

Study Notes

Essential Amino Acids

  • There are essential amino acids that cannot be synthesized in the human body in adequate amounts and must be supplied in the diet.
  • These amino acids cannot be synthesized by the human body and must be obtained through diet.

Non-Essential Amino Acids

  • Non-essential amino acids are synthesizable in the body and there is no dietary dependency for them.
  • These amino acids can be synthesized by the human body and do not need to be obtained through diet.

Consequences of Deficiency

  • A dietary deficiency or imbalance of any essential amino acid can have severe consequences.

Semi-Essential Amino Acids

  • Semi-essential amino acids are synthesized by the healthy adult human body in amounts that are sufficient, but may not be enough in certain conditions, requiring dietary supplementation.
  • Arg and His are semi-essential amino acids that require dietary supplementation in certain conditions, such as in the case of infants or individuals with certain medical conditions.

Conditional Essentiality

  • Tyrosine becomes an essential amino acid in the absence of phenylalanine, and requires dietary supplementation.
  • Cysteine becomes an essential amino acid in the absence of methionine, and requires dietary supplementation.

Dietary Sources of Essential Amino Acids

  • The main dietary sources of essential amino acids are animal proteins, such as meat, eggs, and dairy products, and plant-based proteins, such as legumes, nuts, and seeds.
  • These proteins are characterized as complete proteins, meaning they contain all the essential amino acids.

Dietary Deficiencies

  • Under certain dietary deficiencies, some amino acids become essential and require dietary supplementation.
  • For example, tyrosine becomes essential in the absence of phenylalanine, and requires dietary supplementation.

Non-Essential Amino Acids

  • Non-essential amino acids are considered diet-independent and do not require dietary supplementation.
  • These amino acids can be synthesized by the human body and are metabolically significant.

Classification of Amino Acids

  • Amino acids can be classified as glucogenic, ketogenic, or mixed.
  • Glucogenic amino acids can be converted to carbohydrates.
  • Ketogenic amino acids produce acetyl-CoA or acetoacetyl-CoA.
  • Mixed amino acids produce glycolytic intermediates as well as acetyl-CoA derivatives.

Unusual Amino Acids

  • Unusual amino acids are formed through modification, such as hydroxyproline and hydroxylysine.
  • These amino acids are created through post-translational modification.

Selenocysteine

  • Selenocysteine (Sec) is the 21st amino acid of proteins.
  • It is present at the active site of several enzymes and is associated with antioxidant activity.
  • Selenocysteine is formed during translation and has a special tRNA specific for the ‘UGA’ (STOP) codon.

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Test your knowledge on the classification of amino acids as essential or non-essential based on their synthesizability in the human body.

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