Alcohol Metabolism

Question 1

Where is alcohol metabolised?

Answer 1

Liver

Question 2

Roughly how much of alcohol is metabolised and what happens to the remainder?

Answer 2

> 90%, remainder excreted in urine or on breath

Question 3

What enzyme oxidises alcohol to acetaldehyde?

Answer 3

Alcohol dehydrogenase

Question 4

What enzyme converts acetaldehyde to acetate?

Answer 4

Aldehyde dehydrogenase

Question 5

What is the acetate derived from alcohol converted to?

Answer 5

Acetyl CoA for use in TCA cycle or fatty acid synthesis

Question 6

Smaller amounts of alcohol can also be oxidised by which enzymes?

Answer 6

Cytochrome P450 2E1 enzyme or catalase in brain

Question 7

What are the recommended limits of alcohol per week?

Answer 7

14 units/week spread over at least 3 days for both men and women

Question 8

How many grams of ethanol in one unit of alcohol?

Answer 8

8g

Question 9

What is the rate of alcohol elimination?

Answer 9

7g per hour (roughly)

Question 10

The accumulation of what molecule causes the symptoms of a hangover?

Answer 10

Acetaldehyde

Question 11

What is also produced from the oxidation of ethanol to acetaldehyde and also the oxidation of acetaldehyde to acetate?

Answer 11

NADH (from NAD+)

Question 12

Why does aldehyde dehydrogenase work at a high rate and usually keep acetaldehyde toxicity to a minimum?

Answer 12

Enzyme has a low m for acetaldehyde

Question 13

What is cirrhosis?

Answer 13

Cirrhosis is scarring of the liver caused by continuous long-term liver damage. Scar tissue replaces healthy tissue in the liver and prevents the liver working properly.

Question 14

What causes liver damage?

Answer 14

Accumulation of acetaldehyde

Question 15

What causes changes in liver metabolism?

Answer 15

Excess NADH and acetyl-coA

Question 16

What is alcoholic hepatitis?

Answer 16

Inflammation of the liver due to excessive intake of alcohol

Question 17

What initial two things does alcohol oxidation cause?

Answer 17

1) Decrease in NAD+/NADH ratio

2) Increase in Acetyl-CoA

Question 18

What are the effects of the decreased NAD+/NADH ratio caused by alcohol oxidation?

Answer 18

1) Inadequate NAD+ for conversion of lactate to pyruvate
2) Inadequate NAD+ for glycerol metabolism
3) Inadequate NAD+ for fatty acid oxidation

Question 19

What are the results of inadequate NAD+?

Answer 19

1) Accumulation of lactate - lactc acidosis, accumulation of urate crystals causing gout
2) Deficit in gluconeogensis - hypoglycaemia
3) Increased synthesis of triacylglycerol - fatty liver

Question 20

What are the effects of increased acetyl-coA due to oxidation of alcohol?

Answer 20

Increased synthesis of fatty acids and ketone bodies, increased synthesis of triacylglycerol, fatty liver

Question 21

What drug is used to treat alcohol dependence?

Answer 21

Disulfiram

Question 22

What does disulfiram inhibit?

Answer 22

Aldehyde dehydrogenase

Question 23

What are the effects of taking disulfirim?

Answer 23

If patient drinks alcohol, acetaldehyde will accumulate and cause symptom of a hangover. It therefore acts as a detterent.