Toxicity

Question 1

What is methaemaglobin?

And methaemaglobinaemia?

Answer 1

Oxidised haemaglobin (iron is in the ferrous Fe 2+ rather than ferric Fe3+ state).

Methaemaglobin causing reduced oxygen-carrying capacity.

Question 2

What are the enzymes to correct ferric to ferrous iron?

Answer 2

Cytochrome-B5-reductase, NADPH-MetHb reductase

Question 3

Why and how does methaemaglobin cause a left shift?

Answer 3

The presence of ferrous iron (Fe3+) causes the oxygen-dissociation curve to shift left. This is because it causes oxygen to bind strongly to ferrous iron and impairs release of oxygen to the tissues.

Question 4

What in onion and garlic casues toxicity? And how?

Answer 4

They contain N-propyl disulfide and binds to RBC receptors and cause oxidative damage.

Question 5

What is the normal composition of haemaglobin?

Answer 5

Haemaglobin is a protein on RBC which are made in the bone marrow. It contains alpha- and beta-chains and ferric iron.

Question 6

How does cytochrome-b5-reductase work to reduce methaemaglobin?

Answer 6

Glycolysis results in NADH, which is then used to reduce methaemoglobin back to functional haemaglobin.