Biochemistry Flashcards
How is ammonia a potent neurotoxin?
Ammonia is bioreactive with aldehydes, and can alter behavior of proteins/gene materials
The concentration of ammonia and ammonium ion in the blood is very (high/low)
Low
(T or F) NH3 can easily diffuse through cell membranes
True
Nitrogen is carried to the liver in the form of ____, _____, and _____.
Alanine, glutamine, and ammonia
__% of Nitrogen waste is in urea to be excreted from the body. This helps to keep NH4+ and NH3 levels in the body low.
85%
_______ and _______ reactions funnel amino groups in the urea cycle.
Transamination and de-amination reactions
Carbamoyl phosphate synthetase I (CPS I) is located in the ______
Matrix of the mitochondria
Ornithine reacts with carbamoyl phosphate to form ________
Citrulline
Aspartate reacts with citrulline forming ________. Two “high energy” bonds are required.
Arginosuccinate
Arginine and fumarate are formed from the cleavage of ___________.
Arginosuccinate
Fumarate carbons can be converted into oxaloacetate by ________.
Transamination
Arginine is cleaved into ______ and urea.
Ornithine
Ornithine moves from the (cytosol/matrix) into the (cytosol/matrix)
Cytosol into the matrix
Citrulline moves from the (cytosol/matrix) into the (cytosol/matrix)
Matrix into the cytosol
Fumarate is a ______ intermediate
Krebs cycle
Sources of Nitrogen for the Urea Cycle:
Ammonia is derived from oxidative deamination of _______ by ______ _________.
Glutamate by glutamate dehydrogenase
Glutamate receives amino groups from amino acids through _________.
Transamination
Glutamine and asparagine can donate _____ nitrogens.
Amide nitrogens
Amine oxidases release ammonia from ______, ________, and _______.
Epinephrine, serotonin, and histamine
Bacterial ureases act on amino acids in dietary protein and from urea diffusing into the gut with digestive fluids. Bacterial ureases convert urea in the intestinal fluids into ______ and _____.
NH3 and NH4+
Forms of ammonia released by ureases is pH dependent. Charged (NH4+) (diffusible/non-diffusible) through tissue, and uncharged (NH3) and (diffusible/non-diffusible) through tissue.
NH4+ non-diffusible
NH3 diffusible
At physiologic pH, (NH3 or NH4+) is produced, which is eliminated in the stool
NH4+
Glutamine is synthesized from _______.
Using the enzyme glutamine synthase, (same answer) combines with ammonia, and ATP.
Glutamate
When there is increased Nitrogen, N-acetylglutamate is the activator of ______, which provides short-term regulatory control.
CPS I
A high protein diet or prolonged fasting (deactivates/activates) the urea cycle
Activates
Hyperammonemia results from the inability to detoxify ____ in the urea cycle, leading to elevated blood levels of ammonia
NH4+ (Ammonium)
Hereditary hyperammonemia results from defects in urea cycle _____.
Enzymes
Acquired hyperammonemia most commonly occurs in ________ and ______ due to disruption of the urea cycle
Alcoholic cirrhosis and Reye’s syndrome
In _______, the architecture of the liver is distorted, leading to shunting of portal blood into the hepatic vein, or backup of blood in the portal vein (i.e., portal hypertension)
Cirrhosis
In ________, the function of the urea cycle is disrupted by diffuse fatty changes in hepatocytes and damage to the mitochondria by salicylates.
Reye’s Syndrome
Reye’s syndrome occurs primarily in ______ with _______ who are given salicylates
In children with influenza/chicken pox
Sxs of hyperammonemia
Feeding difficulties, vomiting, ataxia, lethargy, irritability, poor intellectual development, coma. Death may result if sxs not treated.
Non-pharm tx for hyperammonemia
Low-protein diet
Renal Fuel Metabolism:
Glucose is mainly made by the cells of the _______
Renal medulla
Renal Fuel Metabolism:
The renal medulla: _______ glycolysis (no mitochondria) > Lactate
Anaerobic glycolysis
Lactate is largely oxidized by the cells of the ________
Renal cortex
The renal (cortex/medulla) is more metabolically active.
Renal cortex
__________ is also a primary fuel of the kidneys in normal fasting conditions
Glutamine
_______ serves as an amino group carrier from the kidneys. It carried nitrogens to the urea cycle, and is a precursor for gluconeogenesis.
Alanine
Glycogen accumulates in the renal (cortex/medulla)
Renal medulla
Cells of the medulla lack __________, cannot release glucose (no gluconeogenesis)
Glucose-6-phosphatase
_______ cells possess full set of gluconeogenic enzymes. (gluconeogenesis in fasting state - do NOT store glucose)
Cortical
_______ is the most important renal gluconeogenic substrate
Lactate
In hypoglycemia, there is an (increase/decrease) in renal glucose release
Increase
Renal glucose release in T2DM is (increased/decreased)
Increased
Insulin (increases/suppresses) renal glucose release and
(increases/suppresses) glucose uptake.
Suppresses renal glucose release
Increases glucose uptake
Insulin (increases/reduces) fatty acid uptake
Reduces
Epinephrine (increases/decreases) renal gluconeogenesis
Increases
GLUT2 is sodium (independent/dependent) and is the main protein for release of renal glucose into the circulation
Sodium independent
SGLT2 is sodium (independent/dependent) and re-absorbs 90% of proximal tubular glucose
Sodium dependent
GLUT1 transporters in the later segment change the affinity for glucose how?
Increase affinity in later segment because there is not much glucose left, and they want to be sure to capture all the glucose remaining.
_________ is a basic amino acid at body pH, produced in the detoxification of ammonia
L-arginine
Renal synthesis of arginine accounts for __% to ___% of endogenous supply
5% to 15%
_______ is released from the small intestine and is the precursor for arginine synthesis
Citrulline
Creatinine is a marker of _______ function
Kidney
_______ is formed from phenylalanine
Tyrosine
Half of the ______ in circulation derives from the kidneys
Tyrosine
