Amino acids

Answer 1

Information

Amino acids are organic compounds that combine to form proteins. When proteins are digested, amino acids are left. The human body requires a number of amino acids to grow and breakdown food.

Amino acids are classified into two groups:

• Essential amino acids cannot be made by the body and must be supplied by food. These include cysteine, lysine, and tryptophan. Sources of essential amino acids include milk, cheese, eggs, certain meats, vegetables, nuts, and grains.
• Nonessential amino acids are made by the body from the essential amino acids or normal breakdown of proteins. They include aspartic acid, glutamic acid, and glycine.

References

Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Rakel D, ed. Integrative Medicine. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington, DC, 1997.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, PantothenicAcid, Biotin, and Choline. National Academy Press, Washington, DC, 1998.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. National Academy Press, Washington, DC, 2000.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine,Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academy Press, Washington, DC, 2004.

Answer 2

Information

Amino acids are organic compounds that combine to form proteins. Amino acids and proteins are the building blocks of life.

When proteins are digested or broken down, amino acids are left. The human body needs a number of amino acids to:

• Break down food
• Grow
• Repair body tissue
• Perform many other body functions

Amino acids are classified into three groups:

• Essential amino acids
• Nonessential amino acids
• 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.

References

Trumbo P, Schlicker S, Yates AA, Poos M; Food and Nutrition Board of the Institute of Medicine, The National Academies. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids. J Am Diet Assoc. 2002;102(11):1621-1630.

Escott-Stump S, eds. Nutrition and Diagnosis-Related Care. 6th ed. Philadelphia PA: Lippincott Williams & Wilkins; 2008.

Reviewed By

Review Date: 02/08/2011

A.D.A.M. Editorial Team: David Zieve, MD, MHA, and David R. Eltz. Previously reviewed by Alison Evert, MS, RD, CDE, Nutritionist, University of Washington Medical Center, Diabetes Care Center, Seattle, Washington (2/8/2011).

Answer 3

Amino acids are the building blocks of proteins. There are 20 different amino acids that can be combined in various sequences to form different proteins. Each amino acid contains an amine group, a carboxyl group, and a side chain that gives it unique properties.