iron homeostasis & metabolism

Question 1

iron in free state is…..

Answer 1

toxic , there for it’s transport and storage must be regulated

Question 2

normal total body iron range

Answer 2

3 - 5 g

Question 3

distribution of iron in body

Answer 3

1- Hb: 65%-75%

2- fixed iron in tissue: 1%

• cytochrome
• peroxidase
• catalase

3- labile tissue iron 15%-30%
  * ferritin
  * hemosidrin
4- plasma iron:0.1%
  *  transferrin

Question 4

average daily iron requirement

Answer 4

15 - 20 mg/day

Question 5

iron regulation

Answer 5

3-6 % of iron intake is only absorbed which is equal to the amount of iron lost due to sloughing of the cells storing iron
0.6 mg/day

Question 6

iron homeostasis depends on ….

Answer 6

iron absorption .as iron loss is usually unregulated

Question 7

• iron sources …..

- difference between heme and non heme

Answer 7

• heme & non heme
• heme is easily absorbed
  (intact by endocytosis)
  while non heme is poorly absorbed by the body

Question 8

G.R

partial gastrectomy is associated with impaired iron absorbtion

Answer 8

as gastrectomy reduces the available gastric juice which plays a very important role in reducing Fe+3 into FE+2

Question 9

reducing agents of Fe+3

Answer 9

• gastric juice & HCl

- ascorbic acid . vit. C

Question 10

factors that decrease iron absorbtion
&
G.R

Answer 10

• phytic acid
• oxylate
• phosphate
  as they form insoluble iron salts

Question 11

other factors affecting iron absorbtion:

Answer 11

• desferrioxamine
• antacids
• tannic acid (percipitates iron)
• tetracyclines & iron bind together
• calcium in dairy food ( decrease )
• infancy / adolscenes / IDA

Question 12

the total body iron is regulated at what level?

Answer 12

at level of duodenal absorption

Question 13

iron transport

Answer 13

• iron is transported via Tf to the bone marrow where it binds to the receptors on the CM of erythrocytes
• ingested by endocytosis
• iron is delivered to mitochondria where heme is synthesised
• Tf transports iron in the circulation where iron is needed
• only 1/3 of Tf ( 35 % ) is saturated with iron

Question 14

total iron binding capacity

TIBC

Answer 14

measures the free Tf that is ready to carry iron

Question 15

cellular absorption of iron

Answer 15

• ferretin binds to ferretin receptors on the cell membrane and is internalized by receptor mediated endocytosis
• Ph of lysosomes helps in separation of iron fron apoferretin
• apoferretin is not degraded by lysosomes instead it reenters the plasma to carry other iron ions to cells in need

Question 16

excess amount of iron is stored in …….

الترتيب المنطقي

Answer 16

1- hepatocyte
2- reticuloendothelial cells of BM & skeletal muscles 
3- cytoplasm 
على شكل 
* ferritin
* hemosidrin

Question 17

ferritin is the predominant storage form of iron

it’s present mostly in…..

Answer 17

• intestinal mucosa
• livre
• spleen
• BM

Question 18

lethal dose of iron overload in children

Answer 18

200 - 300 mg/kg

Question 19

lethal dose of iron overload in adults

Answer 19

100 gm/kg

Question 20

high doses of iron causes:

Answer 20

gastrointestinal symptomps:
1- constipation
2- nausea
3- vomting 
4- diarrhea may occure

Question 21

genetic defects may cause iron overload

Answer 21

1- hereditary hemochromatosis
due to mutation in high iron gene
2- hemosidrosis  
( bronze diabetes )
3- serum iron and tranferrin saturation limit is elevated

Question 22

treatment of iron overload

Answer 22

1- phlebotomy

2- iron chelators

Question 23

volume of plasma

Answer 23

3.5 ml in 70 kg man

5% of body weight

Question 24

volume of blood

Answer 24

8%
men- 5.5 L
women- 5L

Question 25

specific gravity

Answer 25

whole blood: 1.060
blood elements: 1.090
plasma: 1.030

Question 26

viscosity of blood in relation to water

Answer 26

whole blood : 5 times

plasma : 2 times

Question 27

main function of blood

Answer 27

maintaining homeostasis

Question 28

function of blood

Answer 28

1- transport of :

• o2 & co2
• absorbed substances
• non volatile substances
• hormones

2- regulation of body temp.
3- hemostatic function
4- defensive function
5- nutritive function

Question 29

plasma:

• volume
• S.G
• color
• pH
• osmotic pressure

Answer 29

• 5% of body weight ( 3.5 )
• 1.030
• yellow
• 7.4
• crystalloid : 5000mmHg
  colloid : 25mmHg

Question 30

plasma composition

Answer 30

• 90% water
• 6-8 % plasma proteins
• 1% inorganic constituents
• 2% others
  
  • nutrients
  • wastes
  • dissolved gases
  • hormones

Question 31

plasma proteins

Answer 31

1- albumin 4- 4.5 gm/dl
2- globulin 2.5 gm/dl
3- fibrinogen 0.3 %

Question 32

synthesis of plasma proteins

Answer 32

in livre except gamma globulins by lymphocytes

Question 33

G.R

hypoproteinemia

Answer 33

1- starvation
2- nephrosis
3- livre disease

Question 34

A/G ratio is reduced by:

Answer 34

1- livre disease
2- nephrosis
3- infection TB or typhoid which increases gamma globulin synthesis

Question 35

A/G is increased

Answer 35

• hypogammaglobulinemia

- acquired immuno-deficiency syndrome

Question 36

function of plasma proteins

Answer 36

1- effective osmotic pressure
2- viscosity 
3- buffering function
4- clotting of blood
5- defensive function
6- maintain normal capillary permeability
7- act as carriers
8- CO2 carriage
9- some plasma proteins have specific functions
10- protein reserve