3

Question 1

Iron Significance:

Answer 1

• Part of hemoglobin & myoglobin to carry O2 in blood & in muscles.
• Part of heme molecules of iron-binding proteins.
• Part of cytochromes and many oxidation/reduction reactions, so, it is important for energy utilization, being a part of cytochromes.
• Iron is found in 2 forms; reduced ferrous iron (F2+) & oxidized ferric
iron (F3+). So, it acts as both an electron donor & electron acceptor.
• A component of iron-sulfur proteins.

Question 2

Iron is found in 2 forms in food:

Answer 2

1. Heme iron: Only foods derived from
   animal flesh provide heme. So, it’s found in meats, poultry, fish, (they also contain non-heme iron). - It’s readily absorbed.
2. Non-heme iron: In plants.
   - It’s less absorbed.

Question 3

Intestinal iron absorption increases with:

Answer 3

• Vitamin C.
• ↓ iron stores.
• ↑ erythropoietic activity.
• Anaemia.
• Hypoxia.

Question 4

Intestinal iron absorption decreases in:

Answer 4

Inflammation

Question 5

Excess iron absorption relative to body iron stores:

Answer 5

Hereditary hemochromatosis.

Question 6

• The majority of iron is absorbed in the ………..

Answer 6

duodenum

Question 7

Inorganic iron is taken up by the intestinal mucosal cells and is bounded to the intracellular protein “…………….”.
Once ….. is saturated with iron, no more can enter.

Answer 7

ferritin

Question 8

Iron absorbed from intestine is stored as ……….. in the intestinal epithelial cells or transported in plasma as ……………….

Answer 8

ferritin
transferrin.

Question 9

Absorption of both inorganic & heme iron is impaired by ………….. .

Answer 9

Calcium

Question 10

Iron is toxic to human body if left free in plasma or in fluid portion of the cells as it can generate the highly toxic
………….

Answer 10

hydroxyl free radical (HO -).

Question 11

In duodenal cells , dietary iron (Fe3+) is reduced to the ferrous state Fe2+ (more soluble) by …

Answer 11

duodenal cytochrome B (ferric reductase).

Question 12

Then Fe2+ →transported into the cell by

Answer 12

divalent metal transporter-1

Question 13

In enterocytes, Fe2+ is released from heme by ………….. ……… ……..
• Fe2+ is released into circulation by another protein called ………….

Answer 13

In enterocytes, Fe2+ is released from heme by heme oxidase enzyme.
• Fe2+ is released into circulation by another protein called ferroprotein-
1.

Question 14

Fe2+ iron is then oxidized to Fe3+ iron by & before binding to transferrin.

Answer 14

Fe2+ iron is then oxidized to Fe3+ iron by ceruloplasmin & ferroxidase II,
before binding to transferrin.

Hephaestin, a protein similar to ceruloplasmin, is thought to have a
ferroxidase activity which is also important to release iron from the
cells as Fe3+, to be transported in plasma by transferrin

Question 15

……………….secreted into the circulation, where it down-regulates
ferroprotein-mediated release of iron from enterocytes, macrophages &
hepatocytes.

Answer 15

Hepcidin

Question 16

There are 2 broad categories that describe iron in the body:

Answer 16

A. Essential (or functional) iron. B. Storage iron.

Question 17

Essential or functional Iron: • The iron which is involved in the normal metabolism of the cells. They
are mainly divided into 3 groups:

Answer 17

1. Heme Proteins: as Hb, myoglobin & others as catalases, peroxidases.
2. Cytochromes.
3. Iron Requiring Enzymes: as xanthine oxidase, cytochrome-C reductase, acyl-CoA dehydrogenase, NADH-reductase &others

Question 18

Storage Iron: present in 2 major compounds;

Answer 18

Ferritin & Hemosiderin

Question 19

Ferritin

Storage Sites……, keeps iron in a l…..,

Answer 19

protein complex. It is the intracellular iron-storage protein.
• Ferritin keeps iron in a soluble & non-toxic form.
• Up to 4,500 Fe3+ atoms are found stored in a ferritin complex.
• Ferritin that is not combined with iron is called “apo-ferritin”.
• Storage Sites: Liver, Bone marrow & Spleen.

Question 20

…………glycoprotein that binds Fe very tightly but reversibly  It is the true carrier of iron.

Answer 20

Transferrin

Question 21

Excretion by 3 main sites :Iron

Answer 21

1. GIT.
2. Kidneys.
3. Shedding cells of the skin.

Question 22

Iron Deficiency
• There are three stages of iron deficiency which are:

Answer 22

1. Iron Storage Depletion : not usually recognized by the patient in which
   serum ferritin ↓.
2. Iron Deficiency: Fe stores are almost exhausted. Biochemically, serum
   ferritin & transferrin saturation are low.
3. Iron Deficiency Anemia : hypochromic microcytic anemia .

Question 23

Causes For Iron Deficiency Anemia:

Answer 23

 Blood loss.
 Increased demand for Fe,
Inflammation
 Inability to absorb Fe
 Phytates

Question 24

Iron Overload
• Iron stores may increase due to :

Cells start to fill with excess of hemosiderin → 2 broad types of Fe overload:

Answer 24

• Excessive absorption, or
• Parental iron therapy or
• Repeated transfusions.

1. Hemosiderosis: Iron overload without cell damage. 2. Haemochromatosis: iron overload associated with injury to cells.

Question 25

SELENIUM:
Biochemical Functions;

Answer 25

SELENIUM:
Biochemical Functions;
Serves as a catalytic component in enzymes & proteins as:
• Glutathione peroxidase (destroys H 2O2).
• Acts with other antioxidants and free radical scavengers.
• Overlaps with vitamin E for antioxidant effects.
• Iodo-thyronine 5’- deiodinase to form rT3; playing an important role
in regulating thyroid hormones during embryological development .
• Thio-redoxin reductase.

Question 26

Selenium:
Sources:

Answer 26

Meat, sea food, whole grains & vegetables.

Question 27

Selenium is stored in the body as …

Selenium Deficiency: may lead to ……

Answer 27

is stored in the body as seleno-cysteine in seleno-proteins.

CVDs

Question 28

Most of cobalt is stored with

Answer 28

vitamin B12

Question 29

Cobalt Sources and Intakes:

Answer 29

Humans obtain vitamin B12 and cobalt from animal foods such as
organ and muscle meat.

Question 30

increased the Absorption and Excretion Cobalt:

Answer 30

• Shared with iron.
• Absorption is increased in patients with:
- deficient iron intake,
- portal cirrhosis
- hemochromatosis.

• Excretion: mainly through urine & small amounts in feces, hair & sweat.

Question 31

IODINE: • The body normally has ……. mg of iodine. More than 75% in ………….. The remaining part in: ………

Answer 31

• The body normally has 20-30 mg of iodine.
• More than 75% in thyroid gland. The remaining part in: Mammary gland, Gastric mucosa & Blood.

Question 32

IODINE Function, Sources

Answer 32

Function: synthesis of thyroid hormones, T4 & T3.
• Food Sources: Foods of marine origin, processed foods, iodized salt.

Question 33

Absorption and Excretion:

IODINE

Answer 33

• Iodine is absorbed in the form of iodide.
• Its excretion is mainly by urine & small amounts from bile are
excreted in feces.

Question 34

Iodine Deficiency:

Answer 34

1. GOITER 2. Endemic Cretinism: o Short stature o Protuberant abdomen o Swollen features

Question 35

ZINC:
Main functions in the body:

Answer 35

• Part of many enzymes, especially enzymes for transfer of CO 2.
• Associated with the insulin hormone.
• Involved in making genetic material & proteins.
• Important to wound healing, taste perception, reproduction (for
sperms), vision (transports, activates Vitamin A) & immune function.

Question 36

ZINC sources, Deficiency symptoms:

Answer 36

Significant sources: Protein-containing foods, red meats, shellfish and
whole grains.

oIn children: growth retardation & delayed sexual maturation. o Impaired immune function & poor wound healing. o Hair loss and eye and skin lesions. o Loss of appetite and abnormal taste.

Question 37

Toxicity symptoms:

ZINC

Answer 37

• Loss of appetite,
• Low HDL.
• Copper & iron deficiencies.

Question 38

Copper Source

Answer 38

Organ meats, seafood, nuts, seeds, cereals & whole grains.
• Milk and milk-products are poor sources.

Question 39

Copper Absorption: mainly from ………… by specific transporters, (Cu+2 ions
are highly insoluble).
• Serum Copper: It circulates in blood bounded to ………..
• Excretion: by ……

Answer 39

• Absorption: mainly from duodenum by specific transporters, (Cu+2 ions
are highly insoluble).
• Serum Copper: It circulates in blood bounded to ceruloplasmin.
• Excretion: by liver into bile → GIT to be excreted in feces.

Question 40

Ceruloplasmin: (6 Cu atoms/molecule).
 Functions: …………….
 Congenital absence of ceruloplasmin → ……………

Answer 40

oxidize Fe+2 to Fe+3 iron for binding to transferrin.
 Congenital absence of ceruloplasmin → tissue iron accumulation
→ “hemochromatosis”.

Question 41

Biochemical Functions of Copper:

Answer 41

 Healing wounds,
 Maintaining the myelin sheath nerve fibers.
*
Essential catalytic cofactor for many cupro-enzymes including:
- Cu, Zn-superoxide dismutase (antioxidant).
- Cytochrome C oxidase (ATP synthesis, neurologic function).
- Lysyl oxidase (stabilizes connective tissue proteins).
- Tyrosinase (melanin synthesis).
- Part of several enzymes required for collagen synthesis.

Question 42

Copper Deficiency:

Answer 42

Acquired deficiency is rare . Manifestations are:
Hypochromic microcytic anemia.
Hypopigmentation of hair and skin
Structural abnormalities in connective tissue (hair, teeth, bone
demineralization) Reduced levels of circulating copper and ceruloplasmin

Question 43

Inborn Errors of Copper Metabolism

Answer 43

Wilson’s
Disease
(Hepato-lenticular Degeneration)

Question 44

Wilson’s
Disease
(Hepato-lenticular Degeneration)

Answer 44

• Autosomal recessive disease due to a mutation in Wilson’s disease
protein gene (ATP7B) → protein that transports excess copper into
the bile,

It is a copper storage disease (mainly liver, CNS & cornea of eye)

Diagnosis based on:
Low Ceruloplasmin levels. *
Corneal copper deposition, Kayser-Fleisher Ring.
*
High liver copper levels.