Biochemistry Lecture 16 - Other Sugars and Alcohol Flashcards
What is the clinical importance of sorbitol (there are two that he went over)
- Sorbitol is converted to fructose for fuel for sperm in the seminal vesicles.
- High levels of glucose can lead to too much sorbitol, which generates high osmotic pressure in the eye, leading to retinopathy (sorbitol dehydrogenase activity is low in the eyes).
In what organs does fructose metabolism occur?
Mostly liver, some in the kidney.
What is aldolase B deficiency involved in and what happens? What is the disease called?
Aldolase B converts fructose-1-P to DHAP or glyceraldehyde. Without it, products do not go on to glycolysis, yet phosphates are being used to phosphorylate fructose (fructose —> fructose-1-P), blocking cellular functions. SERIOUS! Called HEREDITARY FRUCTOSE INTOLERANCE.
What is fructokinase deficiency called? Is it serious?
This is called ESSENTIAL FRUCTOSURIA. It is not that serious because the hexokinases can replace fructokinase function, just not as well.
What are the clinical findings of galactokinase deficiency?
Bilateral cateracts in babies.
What is galactose-1-P-uridylyl transferase deficiency?
Serious disease common in Irish descent, not Asians. Presents when baby ingests milk. Results in jaundice, enlarged liver, vomiting, failure to thrive, poor eating, lethargy, diarrhea, sensitivity to infection. Galactose must be removed from diet. Females will go on to have ovarian failure. Both sexes may experience neuro-psychological problems later in life.
Where does UDP-glucuronic acid come from and what are its uses?
It is made from UDP-glucose and can be used to make glycoproteins and proteoglycans (used in chondroitin sulfate GAG). Also IMPORTANT is that it is coupled with drugs and bilirubin to create more highly soluble compounds for excretion in urine. The enzyme that does that is UDP-alpha-D-glucuronsyltransferase.
What is the disease that results from UDP-alpha-D-glucuronsyltransferase?
Gilbert’s syndrome. Characterized by elevated bilirubin. Peeps are usually asymptomatic.
Where in the GI system is ethanol absorbed?
20% in stomach, 80% in small intestine
Is ethanol soluble in fat?
No, not really
When does BAC peak after alcohol ingestion?
~30 min after ingestion
Is alcohol dehydrogenase polymorphic?
Yes, Asians express a lot of ADH2 and 3, which rapidly converts ethanol to acetaldehyde. Asians have an aldehyde dehydrogenase that is less active, so the aldehyde builds up and is not converted to acetate.
How does alcohol ingestion affect gluconeogenesis?
Alcohol metabolism uses NAD+ (acetaldehyde + NAD+ —> acetate). This results in high NADH/NAD+ levels, which inhibits malate conversion to oxaloacetate and 1,3 BPG to 3-PG (for gluconeogenesis) and promotes pyruvate —> lactate, promoting acidosis.
What is Wernickle-Korsakoff syndrome?
Vitamin (mainly Thiamine aka B1) deficiency in alcoholics as a result of impaired gluconeogenesis and no food intake. Acute symptoms are confusion, ophthalmoplegia, ataxia, which is treated with Thiamine (COAT). Chronic symptoms are retrograde amnesia, anterograde amnesia, confabulation, Korsakoff’s psychosis (RACK).
Do high NADH/NAD+ levels increase triglyceride formation? How?
Yes, it inhibits glycolysis from DHAP/glycerol-3-P in the step that uses NAD+. The only other pathway is to generate triglycerides.
