Q 7: Protein Metabolism: Oxidation & Urea - German Flashcards
(33 cards)
What are the four fates of dietary amino acids?
Protein synthesis
Energy production (Citric Acid Cycle)
Biosynthesis
Urea Excretion
What are the three drivers of protein oxidation?
Normal synthesis and degradation
Protein rich diet
Starvation or diabetes mellitus
Why are proteins broken down if they’re not immediately used?
There is no way to store amino acids/proteins
What is an enzyme precursor that requires a biochemical change for activation (usually cleavage)?
Zymogen
What are the pancreatic zymogens?
Trypsinogen —> trypsin
Chymotrysinogen —> chymotrypsin
Procarboxypeptidase A and B —> carboxypeptidase A and B
What does trypsin do?
It cleaves chymotrypsinogen into chymotrypsin
What are the fates of amino acids?
Used for protein and biosynthesis within cells
Catabolized for energy within cells
Transported to the liver and excreted
What does dietary protein lead to (referring to the cascade of hormones)?
Dietary protein —> gastrin secretion —> HCl release —> pH drop
Dietary protein —> gastrin secretion —> pepsinogen —> pepsin, secretin, and cholecystokinin release
What does pepsin do?
.
What does secretin do?
.
What does cholecystokinin do?
.
Where does most amino acid catabolism take place?
Liver
What are the metabolically important amino acids?
Glutamate
Aspartame
Glutamine
Alanine
(Amine group carriers, precursors and common metabolites, and entry and exit molecules from the citric acid cycle)
Ammonia is toxic to all animals except?
Aquatic animals/fish? They secrete ammonia
What are symptoms of ammonia buildup in mammals?
.
NH4+ does what in the brain?
Disrupts astrocyte K+ uptake
What happens when you get high extracellular K+ in the brain?
GABA inhibition is prevented
Leads to neuronal hyperactivity, seizures, oxidative stress, death
How have animals developed to prevent NH4+ problems in the brain?
The body keeps NH4+ levels in the blood relatively low.
Vertebrates create stable molecules of UREA to avoid NH4+ probs
Birds turn it into uric acid
What are transaminase reactions?
They move amine groups from one ketoacid to another (the new amino acids often become amine carriers)
What happens when you add an amine group to glutamate?
You get glutamine
What makes glutamine a common synthetic precursor?
Its ability to transport NH4+
What allows proteins to function as energy sources?
Glucose-alanine cycle (G-A cycle)
(It will use pyruvate from glycolysis and turn it into alanine which is shuttled to the liver and used in gluconeogenesis to generate glucose)
What amino acids feed into fumarate in the CAC?
Phenylalanine
Tyrosine
What is a glucogenic amino acid?
Amino acid that can be converted to glucose
