Section 3B Flashcards
Where is glycogen found in the most concentration? Muscles or liver?
Most concentration in liver but because there is more muscle in the body it has larger total amount. Muscle stores up to 1-3% of its mass in glycogen and liver is up to 8%
Liver cells can typically store up to what percent of their weight as glycogen?
8%
Amino acid degradation occurs with what process?
Deamination - removal of amine groups from amino acids
What enzymes are required for deamination reactions?
Aminotransferases (also known as transaminases)
What two specific aminotransfersases are needed to degrade amino acids?
Aspartate transaminase (AST) - also called SGOT (serum glutamate-oxaloacetate transaminase) Alanine transaminase (ALT) - also called SGPT (serum glutamate-pyruvate transaminase)
What are the dual purposes of AST and ALT?
- They are involved amino acid degradation in deamination reactions
- They are also used to synthesize non-essential amino acids within liver hepatocytes
High blood levels of AST and ALT are indicative of what?
Liver disease
What happens to the amine groups that are cleaved from the amino acids?
Amine groups are converted into ammonia (NH3) or ammonium ions (NH4+) which are then converted into urea.
Where is all the urea formed in the body synthesized?
The liver
In serious liver disease, ammonia can often accumulate in the blood and lead to a state called what?
Hepatic coma or hepatic encephalopathy
A build up of urea in the blood can lead to a state of what?
Azotemia or Uremia in which high levels of urea can become toxic to a variety of tissues.
Uremia is often a symptom of what disease?
Renal failure.
What is the normal range of blood urea nitrogen (BUN)?
5-26 mg/dL
Elevated BUN can occur with what four things?
- Impaired renal function
- Increased protein intake or catabolism
- GI bleeding (due to intestinal flora creating nitrogenous wastes)
- Dehydration
Where does amino acid degradation almost entirely occur?
Liver
How can the body eliminate excess cholesterol?
via the bile
When is ketogenesis occuring?
Primarily in fasting states or poorly controlled type 1 diabetes mellitus
What 3 hormones does the liver degrade?
- Steroid hormones
- T3
- T4
Iron is stored in the liver as what?
Ferritin
Liver stores what vitamins?
Vitamin A
Vitamin B12
Vitamin D
Liver is by the far the most important organ in this type of metabolism?
Drug metabolism
Why does drug metabolism occur in the liver?
Because of the many enzyme systems. The cytochrome P450 system being most important
Cytochrome P450 enzymes can be found predominantly in the liver but also in what other places?
Intestines
Lungs
Other organs
How are Cytochrome P450 enzymes named?
CYP followed by an arabic number, letter, and another arabic number
What is the purpose of conjugation reactions/
To make metabolites more polar or hydrophilic sometimes after they’ve been created by cytochrome p450 enzymes
Conjugation reactions involve an endogenous substrate such as what being added to a metabolite?
Glucuronic acid
Glutathione
Acetyl CoA
or an Amino acid
What is the most common and important conjugation reaction?
Glucuronidation
CP450 inhibition leads to what?
Decreased metabolic activity of CP450 enzymes leading to decreased metabolism of drugs
3 major types of plasma proteins
Albumin
Fibrinogen
Globulin
Where are the major plasma proteins formed?
All of fibrinogen and albumin as well as 50-80% of globulin are formed in the liver
Where is the plasma protein globulin formed?
50-80% in the liver
Remaining is in the lymphoid tissues
What blood clotting factors are synthesized in the liver?
I, II, V, VII, VIII, IX, X, XI, XII
not III, IV or VI
What is the organic recipe for bile?
Bile salts (50%)
Phospholipids (40%)
Cholesterol (4%)
Bile pigments such as bilirubin (2%)
Other than the 4 constituents of bile, what else does it contain and where are they secreted from?
Electrolytes and water which are secreted by cells lining the bile ducts
Hepatocytes synthesize what two primary bile acids?
Cholic acid and chenodeoxycholic acid
What are the two secondary bile acids and how are they made?
- Deoxycholic acid
- Lithocholic acid
They are made as intestinal bacteria convert primary bile acids into secondary bile acids
The liver conjugates the bile acids with what two amino acids to form bile salts?
Glycine or Taurine
What is the most common phospholipid in the bile
Lecithin
T or F, phospholipids are Amphipathic
True
Hepatic synthesis of bile acids accounts for the majority of the breakdown of what?
Cholesterol
How much cholesterol is converted to bile acids and eliminated in bile each day
500 mg
What is bilirubin?
A waste product of hemoglobin degradation
What are the two different types of bilirubin and their many different names?
- Free or unconjugated or indirect bilirubin
2. Conjugated or direct bilirubin
As bilirubin passes into the liver and is released from albumin, hepatocytes has three functions.
- Uptake of bilirubin from circulation
- Conjugation of bilirubin
- Excretion of bilirubin into bile
What is attached to bilirubin during conjugation and what enzyme carries out this function?
Glucuronic acid is attached
Enzyme: Glucuronyl transferase
T or F, Conjugated bilirubin is much more water-soluble than free or unconjugated bilirubin
Treu
Synthesis of bile occurs in what three steps?
- Hepatocytes actively secrete bile into the bile canals (canaliculi)
- Intrahepatic and Extrahepatic ducts not only transport this bile but the cells that line these ducts also secrete a watery, HCO3- rich fluid
- Between meals, approx 1/2 the hepatic bile is diverted to the gallbladder, which stores and removes salts and water
So during meals, the bile that actually reaches the duodenum has what makeup?
It has diluted hepatic bile and concentrated bile from the gallbladder
Bile has what 2 important functions?
- Bile provides the sole excretory route for many solutes that are not excreted by the kidneys
- Secreted bile salts and lecithin are required for normal lipid digestion and absorption in the small intestine
