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Define an amino acid and explain the difference between essential and non-essential...

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coffeeattack | (Level 1) Honors

Posted December 21, 2013 at 3:57 AM via web

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Define an amino acid and explain the difference between essential and non-essential amino acids. Classify six kinds of amino acids according to the functions they serve in the human body, stating an example for each class.

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mwestwood | College Teacher | (Level 3) Distinguished Educator

Posted December 21, 2013 at 5:57 AM (Answer #1)

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As biologically important organic compounds, amino acids are the critical building blocks of protein and are the second largest (after water) component of human muscles, cells, and other tissues. They are composed of amine (-NH2) and carboxylic acid (-COOH). Essential amino acids are those that are absolutely necessary for the utilization of protein to build muscle; these amino acids must be supplied in a person's diet because they cannot be synthesized from scratch, or de novo, to use the scientific term. Non-essential amino acids are those that can be synthesized by the body and are different from essential amino acids that are obtained from food. They are non-essential, not because they are not needed by the body, but because they can be synthesized by the body itself and do not require an outside source.

Three essential amino acids are

  1. Histidine - found in soy protein, eggs, parmesan, sesame, and peanuts, histidine is important in the production of white blood cells.
  2. Lysine - found in soy protein, egges, pork, smelt, and parmesan, this amino acid is also found in small quantities in cereals. It is a major building block of protein, and aids in the construction of muscle protein and the production of hormones and antibodies.
  3. Leucine - found in soy protein, eggs, whitefish, and smelt, leucine is used in the liver and adipose tissue. It also stimulates muscle protein synthesis. 

Three non-essential amino acids are

  1. Glutamine - Digestion and proper brain function and the immune system depend upon glutamine, an amino acide that is the most abundant amino acid in the bloodstream. In addition, studies have also shown glutamine as a possible aide to suppress hunger.
  2. Glycine - Supplying beneficial glucose that the body needs for energy, glycine is essential for proper digestive health and cell function and growth.Glycine comprises a large portion of collagen, a substance which helps skin retain its elasticity and healing properties.
  3. Asparagine - While it helps the nervous system maintain its equilibrium, Asparagine it also acts as a detoxifier, and it regulates metabolism.


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bonyak | eNotes Newbie

Posted January 6, 2014 at 12:00 AM (Answer #9)

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The  above answer is right.

Amino acids are classified into three groups:

  1. Essential amino acids
  2. Nonessential amino acids
  3. Conditional amino acids

Essential amino acids: Essential amino acids cannot be made by the body. As a result, they must come from food.

The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential amino acids: "Nonessential" means that our bodies produce an amino acid, even if we don't get it from the food we eat.

They include: alanine, asparagine, aspartic acid, and glutamic acid.

Conditional amino acids: Conditional amino acids are usually not essential, except in times of illness and stress. They include: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.

You do not need to eat essential and nonessential amino acids at every meal, but getting a balance of them over the whole day is important.


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