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UNDERSTANDING NITROGEN AND ITS USE IN AGRICULTURE
Nitrogenous compounds in human and animal nutrition. The requirement of man and animals is not for
Despite the presence of other amino acids, if
protein per se, but for specific amounts of
the essential amino acids are not all present at
certain amino acids which are the building
the same time and in appropriate proportions,
blocks of the proteins. Animals and humans
human or animal protein cannot be
cannot synthesise the amino group, and in
metabolised. Although over 200 amino acids
order to build up body proteins they must
have been isolated from biological materials,
have a dietary source of amino acids.
only 20 of these are commonly found as components of proteins and of these 9 are essential.
Certain amino acids can be produced from others by a process known as transamination, but the carbon framework of a number of amino acids cannot be synthesised in the animal and human body and these are referred to as indispensable or essential amino acids.
Children Amino acid
Adults
2-5 yr
10-12 yr
18+ yr
mg/kg/day
mg/kg/day
mg/kg/day
Histidine
?
?
8-10
Isoleucine
31
28
10
Leucine
73
44
14
Lysine
64
44
12
Methionine and cysteine*
27
22
13
Phenylalanine & tyrosine
69
22
14
Threonine
37
28
7
Tryptophan
13
3
4
Valine
38
25
10
Total (excl. histidine)
352
216
84
* Sulphur-containing amino acids. Table A : FAO/WHO/UNU (1985) estimates of essential amino acid requirements in pre-school and school-aged children and in adults.
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