Anaemia: Biochemistry

Question 1

how can iron status be tested?

Answer 1

functional iron= Hb
transported iron= serum transferrin
storage= serum ferritin

Question 2

what is normal transferrin saturation?

Answer 2

20-50%

Question 3

define holotransferrin

Answer 3

iron bound to tranferrin

Question 4

what is apotransferrin?

Answer 4

unbound transferrin

Question 5

what is transferrin?

Answer 5

a protein with two binding sites for iron atoms

Question 6

function of transferrin

Answer 6

transports from donor tissues to tissues expressing transferrin receptors

Question 7

donor tissues

Answer 7

macrophages
intestinal cells
hepatocytes

Question 8

what tissues express transferrin receptors?

Answer 8

erythroid marrow

Question 9

when is saturation of transferrin reduced?

Answer 9

iron deficiency

anaemia of chronic disease

Question 10

when is saturation of transferrin increased?

Answer 10

haemochromatosis

Question 11

what does ferritin store?

Answer 11

4000 ferric ions (Fe3+)

Question 12

what is ferritin?

Answer 12

large intracellular protein that is spherical

Question 13

why are tiny amounts of ferritin present in the serum?

Answer 13

reflects ferritin synthesis in response to iron status of host

Question 14

what does serum ferritin also act as?

Answer 14

acute phase protein

Question 15

what causes serum ferritin to increase (acute phase protein)

Answer 15

infection
malignancy
liver injury

Question 16

two forms of iron

Answer 16

ferric (Fe3+)

ferrous (Fe2+)

Question 17

is there a mechanism for iron excretion?

Answer 17

no

Question 18

what enhances absorption of iron?

Answer 18

dedicated haem iron transporter
ascorbic acid (reduces iron to Fe2+)
alcohol

Question 19

what inhibits iron absorption (food examples)?

Answer 19

tannins (tea)
phytates (cereals, bran, nuts, seeds)
calcium (dairy products)

Question 20

mechanisms of iron absorption

Answer 20

duodenal cytochrome B
DMT-1
ferroportin

Question 21

role of duodenal cytochrome B

Answer 21

reduces Fe3+ to Fe2+

Question 22

role of DMT-1

Answer 22

transports ferrous iron into duodenal enterocyte

Question 23

role of ferroportin

Answer 23

facilitates iron export from enterocytes and passed to transferrin

Question 24

what regulates iron absorption?

Answer 24

hepcidin

Question 25

what produces hepcidin?

Answer 25

liver

Question 26

what causes hepcidin to be produced?

Answer 26

increased iron load | inflammation

Question 27

action of hepcidin

Answer 27

binds to ferroportin causing its degradation so iron is trapped in duodenal cells and macrophages

Question 28

what causes hepcidin levels to decrease?

Answer 28

iron deficiency

Question 29

consequences of iron deficiency

Answer 29

low ferritin low MCV microcytic anaemia epithelial changes (skin, koilonychia and angular cheilitis)

Question 30

causes of iron deficiency

Answer 30

diet insufficiency losing too much blood not absorbing enough

Question 31

causes of diet insufficiency of iron intake

Answer 31

vegetarian diets

Question 32

causes of blood loss

Answer 32

``` menorrhagia GI tumours occult ulcer NSAIDs haematuria ```

Question 33

causes of lack of absorption

Answer 33

Coeliac's | achlorhydria (vitamin C needed to absorb iron)

Question 34

describe the macrophage iron block in inflammation

Answer 34

ferritin synthesis increased increased hepcidin reducing iron release decrease iron for erythroblasts

Question 35

what is the macrophage iron block for?

Answer 35

protective mechanism as microorganisms like iron

Question 36

what are B12 and folate?

Answer 36

co-factors in maturation of blood cells and nervous system

Question 37

where is B12 found?

Answer 37

animal food products

Question 38

digestion of B12

Answer 38

acid in the stomach allows it to bind to intrinsic factor from gastric parietal cells alkaline environment activates it travels to jejunum/ileum before entering bloodstream

Question 39

where are dietary folates found?

Answer 39

plant foods

Question 40

absorption of folates

Answer 40

converted to monoglutamate and absorbed in jejunum

Question 41

causes of B12 and folate deficiency

Answer 41

``` alcoholics Coeliac's Crohn's haemolysis pregnancy malignancy anticonvulsants ```

Question 42

body stores of B12

Answer 42

2-4 years

Question 43

body stores of folate

Answer 43

4 months

Question 44

daily requirements of B12 and folate

Answer 44

``` B12= 1.5ug/day folate= 200ug/day ```