Blood Urea Nitrogen Test (Lab)

Urea Cycle

2 ammonia molecules are added to a carbon dioxide molecule to form urea (NH2)2CO

Gastrointestinal microorganisms

Convert dietary amino acids into ammonia in the gastrointestinal system

Blood Urea Nitrogen Test (BUN)

Measures the amount of nitrogen in the blood that comes from the waste product of urea; conducted to see how well your kidneys are functioning

Lipogenesis

The keto acid may be converted to fat via:

Gluconeogenesis

The keto acid may be converted to glucose via:

Citric Acid Cycle

The keto acid may be oxidized as a source of energy via:

Ammonia

Very toxic; most of the time is converted by the liver cells to less toxic urea which is released into the blood and excreted by the kidneys into the urine; also produced by the catabolism of amino acids in peripheral tissues, especially skeletal muscle

Kidney damage

Can elevate BUN level because kidneys are not able to remove urea from the blood; elevated in both acute and chronic renal failure

Liver disease or damage

Can lower your BUN level because most of the urea is produced in the liver

Urea

Comes from the breakdown of proteins - specifically the amino acids that are building blocks of proteins; ammonia that is converted in liver cells to this less toxic form

Uremia

Condition when the kidneys are not able to remove urea from the blood normally, causing BUN levels to rise

Keto Acid Modification

Keto acids formed during transamination are altered so they can easily enter the Krebs cycle pathway

Protein

A diet high in this can make BUN levels higher?

The intestine

A good portion of the ammonia converted in the gastrointestinal system that that is then put into the portal circulation, taken up by the liver and converted in the liver, via the urea cycle, into urea was originally absorbed through what?

Transamination

An amino group is switched from an amino acid to a keto acid

Congestive Heart Failure

Leads to a low blood pressure and consequent reduced filtration rates through the kidneys; therefore, BUN may be elevated

Deamination

The process in which an amino group is removed from an amino acid; excess amino acids are metabolized; process happens in the liver and to a lesser extent in the kidneys; the amino group (NH2) that is removed becomes a molecule of ammonia (NH3)

Keto acid

The rest of the amino acid (after deamination) that is made up of mostly carbon and hydrogen

Glutamine (most tissues), Alanine (muscle)

Transport of ammonia to the liver for urea synthesis, using as the carrier either: