Alcohol Metabolism

Question 1

Where is the major site of alcohol metabolism, what enzyme is involved and what is produced

Answer 1

Liver

Alcohol dehydrogenase

Acetaldehyde

Question 2

What is acetaldehyde oxidised further to and by which enzyme

Answer 2

Acetate

Aldehyde dehydrogenase

Question 3

What is used up and what is produced during alcohol oxidation

Answer 3

NAD⁺ is reduced to NADH

Question 4

What are the effects of a decreased NAD+/NADH ratio on liver cell metabolism

Answer 4

NAD+ levels become inadequate for fatty acid oxidation, conversion of lactate to pyruvate and glycerol metabolism

Decreased lactate metabolism may cause lactic acidosis - lactate accumulates in blood

Increased lactate levesl reduce kidney’s ability to excrete uric acid which may exacerbte gout

Low NAD+ and inability of hepatocytes to use lactate and glycerol means gluconeogenesis cannot be activated

Question 5

What is the effect of increased availability of acetyl CoA

Answer 5

Increased synthesis of fatty acids and ketone bodies

Fatty acids converted to triacylglycerols but these cannot be transported out the liver cells because of lack of lipoprotein synthesis, so they contribute to fatty liver

Question 6

What are the effects of damage to liver cells caused by toxic effects of acetaldehyde

Answer 6

Reduced ability to take up and conjugate bilirubin - hyperbilirubinaemia and jaundice

Reduced capacity to produce urea - hyperammonaemia and increased glutamine

Reduced protein synthesis by hepatocytes

Low serum albumin - may produce oedema

Decreased clotting factors - increased clotting time

Failure to produce adequate amounts of lipoproteins - fatty liver as lipids not transported

Question 7

What indirect effects can there be with excessive alcohol consumption

Answer 7

Poor dietary habit

Vitamin and mineral deficiencies

Inadequate protein and carbohydrate intake

Question 8

What are the effects of alcohol on the GI tract

Answer 8

High concentrations of alcohol damage cells lining GI tract

Often patient has loss of appetite, diarrhoea and impaired absorption of certain nutrients - Vit K, folic acid

Question 9

How can chronic heavy alcohol consumption affect the pancreas and what are the symptoms

Answer 9

Cause chronic pancreatitis

Symptoms: constant pain in upper abdomen radiating to the back, weight loss

Question 10

What drug is used in alcohol dependence and what enzyme does it inhibit

Answer 10

Disulfiram - inhibits aldehyde dehydrogenase

Causes symptoms of a hangover as acetyladehyde will accumulate in the blood