Term
|
Definition
| the hormone secreted by the gastric mucosa when there is entry of dietary protein into the stomach; it stimulates the secretion of hydrochloric acid by the parietal cells & pepsinogen by the chief cells of the gastric glands |
|
|
Term
|
Definition
| an inactive precursor (zymogen) which is converted to active pepsin by an autocatalytic cleavage that occurs only at low pH |
|
|
Term
|
Definition
| the hormone secreted as the acidic stomach contents pass into the small intestine & the pH becomes low; released into the blood |
|
|
Term
|
Definition
| the hormone released into the blood due to the arrival of amino acids in the upper part of the intestine; stimulates secretion of several pancreatic enzymes with activity optima at pH 7 to 8 |
|
|
Term
| 3 zymogens that are synthesized & secreted by the exocrine cells of the pancreas |
|
Definition
1. trypsinogen (becomes trypsin)
2. chymotrypsinogen (becomes chymotrypsin)
3. procarboxypeptidases A & B (become carboxypeptidases A & B) |
|
|
Term
|
Definition
| converts trypsinogen to its active form (trypsin); a proteolytic enzyme secreted by intestinal cells |
|
|
Term
| pancreatic trypsin inhibitor |
|
Definition
| a protein which is a specific inhibitor made by the pancreas to protect itself against self-digestion; effectively prevents premature production of active proteolytic enzymes within the pancreatic cells |
|
|
Term
|
Definition
| hydrolyzes successive amino-terminal residues from short peptides |
|
|
Term
|
Definition
| a disease caused by obstruction of the normal pathway by which pancreatic secretions enter the intestine |
|
|
Term
| amino-transferases (transaminases) |
|
Definition
| enzymes which promote the removal of the alpha-amino groups from most L-amino acids once they have reached the liver for the first step of catabolism |
|
|
Term
|
Definition
| the alpha-amino group is transferred to the alpha-carbon atom of alpha-ketoglutarate, leaving behind the corresponding alpha-keto acid analog of the amino acid |
|
|
Term
| pyridoxal phosphate (PLP) |
|
Definition
| a prosthetic group; the coenzyme form of pyridoxine (vitamin B6) |
|
|
Term
| What is the relationship between oxidative deamination & L-glutamate dehydrogenase? |
|
Definition
| in hepatocytes, glutamate is transported from the cytosol into the mitochondria where it undergoes oxidative deamination catalyzed by L-glutamate dehydrogenase |
|
|
Term
|
Definition
| the combined action of an aminotransferase & glutamate dehydrogenase |
|
|
Term
|
Definition
| allows for the free ammonia produced in tissues to combine with glutamate to yield glutamine |
|
|
Term
|
Definition
| a pathway in which alanine plays a special roe in transporting amino groups to the liver in a nontoxic form |
|
|
Term
|
Definition
| allows for glutamate to transfer its alpha-amino group to pyruvate (a readily available product of muscle glycolysis) as an alternative to glutamate being converted to glutamine for transport to the liver |
|
|
Term
|
Definition
| most aquatic species (ex. bony fishes) are ammonotelic; they excrete amino nitrogen as ammonia |
|
|
Term
|
Definition
| most terrestrial animals are ureotelic; they excrete amino nitrogen in the form of urea |
|
|
Term
|
Definition
| how the ammonia deposited in the mitochondria of hepatocytes is converted to urea in ureotelic organisms |
|
|
Term
|
Definition
| cleaves argininosuccinate; forms free arginine & fumarate (fumarate is converted to malate before entering the mitochondria to join the pool of citric acid cycle intermediates) |
|
|
Term
| What is the relationship between arginase & urea? |
|
Definition
| in the last reaction of the urea cycle, the cytosolic enzyme arginase cleaves arginine to yield urea & ornithine |
|
|
Term
| aspartate-argininosuccinate shunt |
|
Definition
| provides metabolic links between the separate pathways by which the amino groups & carbon skeletons of amino acids are processed |
|
|
Term
| What is the relationship between N-acetylglutamate & N-acetylglutamate synthase? |
|
Definition
| Carbamoyl phosphate synthetase I is allosterically activated by N-acetylglutamate which is synthesized from acetyl-CoA & glutamate by N-acetylglutamate synthase |
|
|
Term
|
Definition
| the half of the 20 common amino acids which humans are incapable of synthesizing; must be provided in the diet |
|
|
Term
| tetrahydrofolate (H4 folate) |
|
Definition
| synthesized in bacteria & consists of substituted pterin, p-aminobenzoate, & glutamate moieties |
|
|
Term
| S-Adenosylmethionine (adoMet) |
|
Definition
| the preferred cofactor for biological methyl group transfers |
|
|
Term
| methionine adenosyl transferase |
|
Definition
| synthesizes adoMet from ATP & methionine |
|
|
Term
|
Definition
| yielded by the transfer of the methyl group from S-Adenosylmethionine to an acceptor; is broken down to homocysteine & adenosine |
|
|
Term
|
Definition
| the B12 deficiency disease; a rare disease seen only in individuals who have a defect in intestinal absorption pathways for this vitamin or in strict vegetarians |
|
|
Term
|
Definition
| the anemia associated with vitamin B12 deficiency |
|
|
Term
|
Definition
| immature precursor cells in the bone marrow whose appearance (along with a decline in the production of mature erythrocytes) is associated with megaloblastic anemia |
|
|
Term
|
Definition
| abnormally large erythrocytes which gradually replace erythrocytes in the blood in smaller numbers in individuals with megaloblastic anemia |
|
|
Term
| What is the relationship between alanine & tryptophan? |
|
Definition
| alanine yields pyruvate directly on transamination with alpha-ketoglutarate & the side chain of tryptophan is cleaved to yield alanine & thus pyruvate |
|
|
Term
| 7 amino acids who have portions of their carbon skeletons that yield acetyl-CoA and/or acetoacetyl-CoA (which is converted to acetyl-CoA) |
|
Definition
1. tryptophan
2. lysine
3. phenylalanine
4. tyrosine
5. leucine
6. isoleucine
7. threonine |
|
|
Term
| What is the relationship between phenylalanine hydroxylase & phenylketonuria (PKU)? |
|
Definition
| a genetic defect in phenylalanine hydroxylase (the first enzyme in the catabolic pathway for phenylalanine) is responsible for the disease PKU (the most common cause of elevated levels of phenylalanine in the blood) |
|
|
Term
|
Definition
| yielded when phenylalanine undergoes transamination with pyruvate |
|
|
Term
| What is the relationship between alkaptonuria & homogentisate dioxygenase? |
|
Definition
| an inheritable disease of phenylalanine catabolism (alkaptonuria) is caused by a defect in the enzyme homogentisate dioxygenase |
|
|
Term
| 2 amino acids which contain five adjacent carbons & a sixth carbon attached through a nitrogen atom |
|
Definition
|
|
Term
| branched-chain alpha-keto acid dehydrogenase complex |
|
Definition
| catalyzes oxidative decarboxylation of all three alpha-keto acids, in each case releasing the carboxyl group as CO2 & producing the acetyl-CoA derivative |
|
|
Term
| maple syrup urine disease |
|
Definition
| named because of the characteristic odor imparted to the urine by the alpha-keto acids, it results from a defective branched-chain alpha-keto acid dehydrogenase complex |
|
|
