The answer is B because viruses don't need to be fed.
Answer:
a. antigen
Explanation:
The Immune system is composed of immune cells that defend the body against foreign substances such as bacteria or virus. Lymphocytes (B and T cells) are one of the main immune cells
Lymphocytes have the ability to recognize and bind to antigens, wich are substances foreign to the body ( i.e bacterial or virus elements) that evokes an immune response.
Aspartate + a- keto acid >> Oxaloacetate + a amino acid
This reaction is occur because the a- keto acid in the equation can come from any amino acid, the 15 N from aspartate is rapidly transferred to other amino acids.
15N is symbol use as the isotope of nitrogen with mass number 15. comprises of 0.4 % of stable nitrogen found, so the relative abundance of each in amino acid is simply a reflection of how much is found in nature in general.
This isotopes is enrichment of the labelled amino acids was determined following a previously developed procedure comprising by determination of the spectral purity of the selected natural abundance amino acids.
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