Answer to Question 1
Protein catabolism involves removing the nitrogen-containing amino group and using the remainder of the amino acid to generate energy. Transamination, the first step in this process, includes transferring the amino group from an amino acid to a compound called an -ketoacid to form a new amino acid.
Deamination, the second step of amino acid catabolism, occurs primarily in the liver. This process removes the amino group from an amino acid, leaving an -ketoacid. The amino group removed from the amino acid is converted to ammonia. Because ammonia is toxic to cells, it is quickly converted to a less toxic substance called urea, which is released into the blood. Urea is removed from the blood by the kidneys and excreted in the urine. Deamination also produces NADH + H+, which then produces energy through oxidative phosphorylation via the electron transport chain.
After transamination and deamination are complete, an -ketoacid is able to enter the citric acid cycle at various points.
Answer to Question 2
a
C:N ratios differ a great deal among the tissues of pines and between the woody tissues of pines and
(a) Mammal species from central Saskatchewan differ greatly in their isotopic signatures. (b) There
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