lecture 34 - alcohol metabolism

Question 1

What receptor does alcohol act as an agonist of?

Answer 1

GABA A receptor

Question 2

How does alcohol affect the nervous system?

Answer 2

Acts as an agonist of the GABA A receptor causing an increase in the inhibitory effect on neurotransmission.

Question 3

What type of receptor is the GABA A receptor?

Answer 3

Membrane bound ligand-gated chloride channel

Question 4

What happens when the GABA A receptor is activated?

Answer 4

Selectively conducts Cl- ions causing an inhibitory effect on neurotransmission by reducing the chance of a successful action potential.

Question 5

Does alcohol amplify or dampen the effects of a GABA A receptor?

Answer 5

Amplifies, as it is an agonist, increasing the number of chloride molecules that cab pass through

Question 6

What is the chemical we know as alcohol?

Answer 6

Ethanol

Question 7

Why is alcohol rapidly absorbed into the blood?

Answer 7

Small molecule that does not require enzymatic digestion, so will be readily absorbed and then metabolised.

Question 8

What is alcohol/ethanol converted to when it first enters the body?

Answer 8

Acetaldehyde

Question 9

What enzyme is needed to convert ethanol to acetaldehyde?

Answer 9

Alcohol dehydrogenase

Question 10

What is alcohol dehydrogenase coupled to when forming acetaldehyde from ethanol?

Answer 10

NAD+ is converted to NADH and H+

Question 11

What is acetaldehyde converted to by aldehyde dehydrogenase?

Answer 11

Acetate

Question 12

What enzyme is used to convert acetaldehyde to acetate?

Answer 12

Aldehyde dehydrogenase

Question 13

What is the acetaldehyde to acetate reaction coupled to?

Answer 13

The conversion of NAD+ to NADH and H+

Question 14

How does acetate form Acetyl CoA?

Answer 14

Using Acetyl CoA synthetase enzyme. CoA and ATP are fed into the reaction, AMP and PPi produced

Question 15

What are the consequences of alcohol metabolism on the citric acid cycle and electron transport chain?

Answer 15

Slows CAC and ETC by increasing the NADH to NAD+ ratio

Question 16

What is the effect of alcohol metabolism on fatty acids?

Answer 16

They are esterified to TAG, which can cause a build up in the liver - ‘fatty liver’ as well as high blood cholesterol and TAG concentrations

Question 17

What is the consequence of alcohol metabolism on pyruvate?

Answer 17

Increases the NADH to NAD+ ratio, which causes the pyruvate to lactate reaction, which decreases the pH of the liver.

Question 18

What is the consequence of alcohol metabolism on gluconeogenesis?

Answer 18

Increases [NADH], which inhibits gluconeogenis which can lead to low blood glucose between meals.

Question 19

What happens to the ratio of NADH to NAD+ when alcohol is metabolised?

Answer 19

Increased NADH, decreased NAD+. Increased NADH/NAD+

Question 20

Where is the majority of ethanol metabolised?

Answer 20

The liver

Question 21

What system metabolises alcohol when it is treated as a toxin?

Answer 21

The microsomes ethanol oxidising system

Question 22

What product of ethanol metabolism is toxic?

Answer 22

Acetaldehyde

Question 23

What can the oxidase in ethanol metabolism give rise to?

Answer 23

Reactive oxygen species

Question 24

What is the outcome of chronic fatty liver and inflammation?

Answer 24

Alcoholic hepatitis

Question 25

What are the outcomes of alcoholic hepatitis?

Answer 25

necrosis, cirrhosis, then coma and death

Question 26

What builds up in liver dysfunction?

Answer 26

NH3

Question 27

What limits the rate of alcohol metabolism?

Answer 27

Alcohol dehydrogenase becomes saturated after a couple of drinks, meaning it can only catalyse the reaction to acetaldehyde at a limited rate.

Question 28

What is the impact of alcohol metabolism on citrate levels?

Answer 28

By limiting the CAC and ETC, citrate builds up

Question 29

What is the mechanism by which fatty liver occurs?

Answer 29

Excess alcohol intake causes reduced fatty acid metabolism due to a depletion in NAD+. Fatty acids are instead converted to TAGs, which build up in the liver.