The old adage, "an apple a day keeps the doctor away" may come to mind when you consider the amino acids an apple provides. Amino acids are the building blocks of protein and are classified both by polarity and as either essential, nonessential or conditional. Essential amino acids are those not made by the body and as such, you must obtain them from your diet. Nonessential amino acids are those that your body does produce naturally, while conditional amino acids are those that are usually not essential except in times of illness and stress. The amino acid profile of an apple reveals that this fruit is a good option for boosting your amino acid intake.
Nonpolar Amino Acids
The nonpolar amino acids in apples, so-named because of the polarity of their atoms, include glycine, alanine, valine, leucine, isoleucine, proline, methionine, phenylalanine and tryptophan. One large apple, measuring 3.25 inches in diameter, contains 0.02 grams each of glycine, alanine, valine and leucine, as well as 0.01 grams of isoleucine, proline and phenylalanine and 0.002 grams of methionine and tryptophan. Isoleucine, methionine, valine, leucine and phenylaline are essential amino acids, while alanine is nonessential. Tryptophan, glycine and proline are considered conditional.
Polar Amino Acids
The polar amino acids present in apples are serine, threonine, cysteine and tyrosine. Consume one large apple, and you take in 0.02 grams of serine, 0.01 grams of threonine, 0.002 grams each of cysteine and tyrosine. Threonine is a particularly important amino acid, as it helps stabilize blood sugar. Two polar amino acids not contained in apples are asparagine and glutamine. Serine, cysteine and tyrosine are conditional amino acids; threonine is an essential amino acid.
Acidic-Polar Amino Acids
Apples also contain acidic-polar amino acids, including aspartic acid and glutamic acid. In each large apple, you find 0.15 grams of asparatic acid and 0.05 grams of glutamic acid. Aspartic acid and glutamic acid — both nonessential amino acids — play a critical role in producing enzymes. Aspartic acid influences your nervous system, while glutamic acid helps with brain function. Aspartic acid and glutamic acid are non-essential amino acids,
Basic-Polar Amino Acids
Include an apple in your diet, and you consume all the basic-polar amino acids, as one apple provides 0.02 grams of lysine and 0.01 grams each of arginine and histidine. Lysine is an amino acid that influences cold sore outbreaks and is involved in converting fatty acids to energy. Arginine may help keep your blood vessels healthy, while histidine contributes to cellular growth. Lysine and histidine are essential amino acids, while arginine is a conditional amino acid.
