Albumin and iron

Question 1

Which organ synthesises albumin?

Answer 1

The liver

Question 2

What % of the protein content of blood does albumin constitute?

Answer 2

> 50%

Question 3

What are the two main roles of albumin?

Answer 3

Maintain osmolarity of plasma and prevent oedema or ascites

Binding small molecules, especially metal ions (like copper and zinc) and hydrophobic molecules (like fatty acids, steroid hormones, hydrophobic drugs etc.)

Question 4

What three diseases affect blood albumin concentrations?

Answer 4

Liver disease - decreased capacity for albumin synthesis
Kwashiorkor - low protein diet, less raw material for albumin synthesis
Kidney disease - excessive excretion of albumin in urine

Question 5

What are the major roles of iron in the body?

Answer 5

Constituent of haemoglobin and myoglobin

Involved in DNA replication and metabolism (cytochromes)

Involved in organ function and growth

Can generate ROSs and nitrogen species which can kill invading organisms to aid immune response

Question 6

Dietary intake of iron

Answer 6

8-11mg, more when pregnant and for teenage girls

Question 7

Average whole body iron

Answer 7

2.5g to 5g

Question 8

Amount of iron absorbed (and consequently lost) daily

Answer 8

roughly 1mg

Question 9

What prevents over-absorption of iron and why is it so tightly regulated?

Answer 9

Mucosal block at the level of the enterocyte

Iron cannot be excreted once absorbed by the body

Question 10

Proportion of iron found in haemoglobin (male)

Proportion of iron stored

How much smaller are female stores of iron relative to male and why?

Answer 10

60%

25%

40% less, due to blood loss during menstruation

Question 11

Which hormone monitors iron concentrations?

Answer 11

Hepcidin

Question 12

What will cause an increase in Hepcidin concentrations?

Answer 12

An increase in iron concentrations

Question 13

Where does Hepcidin act?

Answer 13

Ferroportin, reducing its efficacy at iron efflux

Question 14

Which transporter protein exports iron into the plasma?

Where can it be found, and how many mole of iron ions can a mole of ferroportin bind?

Answer 14

Ferroportin

In the duodenum exporting dietary iron and in the liver and spleen exporting recycled iron

Binds 2 moles of Fe3+

Question 15

What molecule carries iron in the blood?

Answer 15

Transferrin

Question 16

Describe the mechanism of iron transport into cells

Answer 16

1. Transferrin, carrying two iron, binds to transferrin receptor
2. Internalised as endosome via clathrin-coated pit
3. Lysosome fuses with endosome, low pH induces Fe3+ release by converting it to Fe2+, allowing it to be transported into cytoplasm through DMT1 (divalent metal transporter 1)
4. Ceruloplasmin oxidises Fe2+ to Fe3+, which can then bind to ferritin