【单选题】Release of amino acid nitrogen and NH4+ is an important step in generating precursors for the urea cycle. Which statement best describes this release of amino acid nitrogen as NH4+ from amino acids?
A.
NH4+ freely diffuses across membranes.
B.
Glutamate deamination by oxidation is readily reversible.
C.
Serine deamination to pyruvate is readily reversible.
D.
Glutamine deamination to glutamate is readily reversible.
【单选题】An individual has been shown to have a deficiency in an intestinal epithelial cell amino acid transport system for leucine. However, the individual shows no symptoms of amino acid deficiency. This cou...
A.
The body synthesizes leucine to compensate for the transport defect.
B.
The kidney reabsorbs leucine and sends it to other tissues.
C.
There are multiple transport systems for leucine.
D.
Isoleucine takes the place of leucine in proteins.
E.
Leucine is not necessary for bulk protein synthesis.