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    Essential, non-essential and conditionally-essential amino acids

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    Part 1

    Explain what the term 'essential' means to you.
    Identify one essential amino acid and describe how it could be obtained in your diet?
    Phenylketonuria (PKU) is a genetic disease that is screened for in newborns. Kwashiorkor is described in your readings this unit as a form of malnutrition caused by inadequate intake of proteins. Compare and contrast these two diseases and their requirements for amino acids.

    Part 2

    Stress-related anxiety is a very common occurrence in society today. Recent studies have shown that life-style choices such as diet may influence stress.
    Article: Smriga, M., & Torii, K. (2003). Prolonged Treatment with l -Lysine and l -Arginine Reduces Stress-induced Anxiety in an Elevated Plus Maze. Nutritional Neuroscience, 6(2), 125.

    There are also dietary amino acid supplements available. Explain if these supplements will work in your body.
    What is an L-Lysine supplement? Who regulates the marketing claims and recommended dosages on these labels?
    Provide one additional example of a situation when an amino acid is conditionally essential.

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    Solution Preview

    I have explained in detail the following topics in the attachment: essential amino acids, PKU, Kwashiorkor, dietary amino acid supplements & their benefits and conditionally essential amino acids. Please go through the references.

    Protein intake and Stress

    Out of the 20 amino acids, humans are unable to synthesize 9 amino acids and they must be provided in diet. These amino acids are known as Essential Amino Acids.

    Figure 1: Shows the essential, conditionally essential and nonessential amino acids (Lehninger, A., Nelson, D. L., & Cox, M. M. (2008). Lehninger Principles of Biochemistry & eBook).

    Isoleucine is an essential amino acid that has the following roles/characteristics in the human body:
    • Required in Hemoglobin formation.
    • Regulates and stabilizes blood sugar levels.
    • It is metabolized in muscles and is a very significant amino acid for athletes for the following reasons:
    a) Enhance energy level
    b) Increase endurance
    c) Muscle tissues are repair and healing requires the supply of isoleucine

    Rich Food Sources of Isoleucine:
    Following food sources are rich in Isoleucine:
    • Soy protein
    • Almonds
    • Seeds
    • Rye
    • Cashew nuts
    • Chicken
    • Eggs
    • Fish
    • Lentils
    • Liver
    • Meat
    • Cheese

    A genetic defect in phenylalanine hydroxylase, the first enzyme in the catabolic pathway for phenylalanine (the conversion of phenyl alanine to tyrosine is affected), is responsible for the disease phenylketonuria (PKU), the most common cause of elevated levels of phenylalanine (hyperphenylalaninemia). When a child with PKU eats food containing Phenyl alanine, it builds up in the blood and causes problems. Phenyl alanine is found in almost every food, except pure fat and sugar.

    Figure 2: The conversion of Phenylalanine to Tyrosine is hampered in PKU due to defect in the enzyme phenyalanine hydroxylase (Lehninger, A., Nelson, D. L., & Cox, M. M. (2008). Lehninger Principles of Biochemistry & eBook).

    Figure 3: Comparing PKU vs. Normal child

    The word Kwashiorkor means "a neglected or rejected child". Lack of protein in the diet of children leads to this problem. Also, children who are not fed breast milk don't get sufficient protein which leads to this disorder. The child is given a diet that has enough carbohydrates but not proteins. Children in African countries are prone to this disease since these children are mainly fed on corn rich diet.
    Corn is deficient in tryptophan, an amino acid that is required to make proteins. However, this disease does not occur in countries that have wheat as a staple food. The disease is often fatal. Symptoms that arise from lack of dietary protein and resulting shortage of amino acid include weight loss, decrease in muscle mass, hair and skin changes, diarrhea, extreme fatigue and immunodeficiency.


    PKU occurs when an enzyme, called "phenylalanine hydroxylase" (PAH), is either missing or not working properly. When the diet is extremely deficient or totally lacking in protein, the body becomes severely ill and a disease called ...

    Solution Summary

    This solution explains in detail the essential amino acids, conditionally essential amino acids, and role of amino acid supplements.It also discusses compares the disorders, Phenylketonuria (PKU) & Kwashiorkor caused due to lack of amino acids and protein deficiency in diet.