BIOCHEMISTRY: DIGESTIVE SYSTEM Flashcards
Describe protein digestion in the stomach and small intestine.
Describe absorption of amino acids in the intestine
Indicate the molecules found in the portal vein following digestion.
There are only free amino acids in the portal vein. These are metabolized by liver or released into circulation.
Portal vein (PV) (sometimes referred to as the main or hepatic portal vein) is the main vessel in the portal venous system and drains blood from the gastrointestinal tract and spleen to the liver.
Describe the primary cellular roles of dietary proteins & Indicate the possible fate of dietary amino acids.
Indicate the major site of protein digestion.
Proteins are denatured by HCl in the stomach, preparing them for digestion by proteases in the small intestine.
Pepsin, which is secreted as pepsinogen by chief cells of the stomach, initiates the degradation of proteins to peptides in the stomach.
Describe the transamination reaction: substrates, products, coenzyme.
Removal of nitrogen from amino acids
• α-amino group removed
Transamination – amino group transferred to α-KG
- products are an α-keto acid and glutamate
- glutamate can be used as a donor of the amino group in the synthesis of other amino acids or can be oxidatively deaminated
- transfer accomplished by aminotransferases
- all aa’s except lysine and threonine participate in transamination
Describe Alanine aminotransferase (ALT) reaction with their products and coenzymes.
Vitamin B6 = Coenzyme
Describe Aspartate aminotransferase (AST) reaction with their products and coenzymes.
Coenzyme = Vitamin B6
Describe the role of glutamate dehydrogenase in producing free ammonia.
Indicate the allosteric regulators (ATP, ADP, GTP, GDP) of glutamate dehydrogenase and how they affect the direction of the reaction.
Describe the metabolism of D-amino acids and the enzyme and coenzyme required.
