MEH alc metabolism

Question 1

what is the effect on TAG synthesis with chronic alc consumption? (triacylglycerol)

Answer 1

increase in TAG synthesis
>since there is inadequate NAD+ for fatty acid oxidation to occur
>and an increase in acetyl-CoA would lead to an increase in fatty acid synthesis and TAG synthesis.

Question 2

what occurs as a result of oxidative damage to proteins?

Answer 2

hydroxylated adducts, di-tyrosine dimers, inappropriate disulphide bond formation and the formation of ring open species.

Question 3

A disulphide bond in a protein can form between two residues of which amino acid?

Answer 3

cysteine

Question 4

which two amino acids contain sulphur?

which cannot form disulphide bonds?

Answer 4

methionine (can’t form disulphide bonds)

and cysteine

Question 5

sources of endogenous free radicals?

Answer 5

*the enzyme transport chain,
peroxidase enzymes,
nitric oxide synthase (nitric oxide is a free radical) lipooxygenases,
NADPH oxidase enzyme (used in “respiratory burst”), Xanthine oxidase
and Monoamine oxidase.

*major source

Question 6

Which enzyme is involved in protecting cells from oxidative damage by converting superoxide to H2O2 and oxygen?

Answer 6

Superoxide dismutase (SOD).

Question 7

Which enzyme protects cells from oxidative damage by converting H2O2 to water and oxygen?

Answer 7

Catalase.

Question 8

Which fat soluble vitamin plays an important role in protecting cells against oxidative damage by acting as a free radical scavenger?

Answer 8

vitamin E (α-tocopherol) plays an important role in protecting cells against lipid peroxidation.

Vitamin C (Ascorbic acid) is a water soluble antioxidant that plays an important role in regenerating the reduced form of Vitamin E.

Question 9

In the treatment of acetaminophen (paracetamol) overdose, which drug can be administered to help maintain or replenish depleted liver glutathione levels?

Answer 9

Acetylcysteine

Question 10

which causes liver damage due to accumulation during paracetamol overdose?

Answer 10

NAPQI

Question 11

what causes a fatty liver?

Answer 11

inc TAG synthesis
reduced capacity to transport with lower lipoprotein synthesis
> accumulation > fatty liver

Question 12

how are superoxide radicals produced by mitochondria

Answer 12

ETC

electrons prematurely reduce oxygen to form superoxide before reaching the end of the ETC

Question 13

list agents in cells that protect against reactive oxygen species

Answer 13

• catalase enzyme
• SOD (superoxide dismutase)
• antioxidant vitamins
• glutathione
• NADPH

Question 14

what is the relationship between NADPH and glutathione?

Answer 14

recycling system/ mopping up ROS

• NADPH reduces oxidised glutathione into its reduced form via GSH reductase.
  > this is then available to be oxidised by ROS > removing them/ mopping them up

Question 15

define oxidative stress

Answer 15

Oxidative stress occurs when the production of ROS is excessive or antioxidant levels are low in a cell, and the balance is shifted in favour of ROS.

Question 16

how is a respiratory burst produced in some leukocytes?

Answer 16

• in neutrophils/ monocytes
• via NADPH oxidative enzymes. transfers electrons from NADPH across the membrane to generate ROS.
  > electrons couple with the molecular oxygen forming superoxide radicals.

Question 17

Explain why acetylcysteine is an effective treatment for paracetamol overdose

Answer 17

It replenishes the Glutathione which is depleted in overdose.