30 Metabolic Processes of the Liver Flashcards
what GLUT transporter transports carbohydrates into the liver?
GLUT2
what is the effect on insulin and glucagon after a meal?
Insulin increases and glucagon decreases
what are the fates of glucose?
Can be broken down for energy (glycolysis)
can be stored as glycogen
galactose and fructose can be converted to glucose
excess carbs are converted to fat
what are the key enzymes in glycolysis?
glucokinase, phosphofructokinase, pyruvate kinase
what is the effect on insulin and glucagon?
Insulin decreases and glucagon increases
so in between meals, what is glycogen broken down into?
glucose for energy
what is the key enzyme that allows glycogen to be broken down into glucose for energy?
Glucose 6-Phosphatase (only in liver) allows glucose to exit the hepatocyte via GLUT2
what does gluconeogensis allow for?
alternate sources of glucose (amino acids, glycerol, lactate)
how are amino acids transported into the liver?
via Na-dependent and Na-independent transport
what are the fates of amino acids?
o Amino acids need to be utilized or broken down immediately
Synthesis of non-essential amino acids (transamination)
Deamination of amino acids yields a-keto acids and ammonia
Synthesis of plasma proteins
why is it that Amino acids need to be utilized or broken down immediately?
No storage form for amino acids
how is the amino acid fate through the synthesis of non essential amino acid?
transaminase
why is the fate of an amino acid the deamination of amino acids yields a-keto acids and ammonia?
a-keto acids can be used for the Krebs cycle, gluconeogenesis and ketogenesis
keep in mind that ammonia is converted to urea and so that Urea leaves the cell at the basolateral membrane
and is Excreted in urine
why does the amino acid fate lead to the synthesis of these plasma proteins?
albumin
blood clotting factors
apolipoproteins
glutathione
what is albumin?
it affects oncotic pressure and carrier proteins
what are apolipoproteins used for?
fat metabolism
what is glutathione used for?
drug metabolism and protection against oxidative stress
what vitamin is involved in blood clotting?
vitamin K
how does fatty acid transport in the lymph and blood work in the form of chylomicrons?
Chylomicrons enter lymphatics in the intestines and then enter the venous system at the root of the neck, thus ending up in the systemic circulation before reaching the liver
in the systemic system, how are the triglycerides broken up?
From the systemic circulation, fat and muscle endothelium lipoprotein lipases partially digest the triglycerides to fatty acids and glycerol for use in the cell
How does FA transport into the liver work?
Chylomicrons reach the liver as chylomicron remnants and so they are taken up by the liver using LDL related receptors
what is contained in the chylomicron?
▪ Chylomicron remnants contain less triglycerides and higher ratio of fatty acids and cholesterol
what is the fate of the FA?
acetyl CoA can be produced
fatty acids can be re-esterified to form triglycerides which are stored or exported as very-low-density lipoprotein (VLDLs)
Liver uses lipids in the synthesis of phospholipids, lipoproteins
What are the three zones of the liver?
zone 1-3
