Which of the following statements are true regarding the function of the liver and the kidney?
1) Excessive amino acids in the body are broken down through 'deamination' in which the amino group (i.e., the N-terminus) of an amino acid is converted to ammonia (NH₃) in the liver
2) Ammonia is toxic to humans (or animals) if it is accumulated in high concentration in the blood which must be removed by converting to urea (less toxic) through the urea cycle in the liver
3) Ammonia is combined with carbon dioxide to form urea (NH2-CO-NH2) via the urea cycle in the liver which is less toxic, and urea can be removed in the kidney, becoming a component of the urine
4) Urea is removed from blood during filtration in the glomerulus of the Bowman's capsule
5) Urea can also be removed from human body in the liver, not from the kidney
6) Ammonia is converted to urea in the kidney
7) Ammonia is converted to urea in the spleen