1. Hemoglobin (Hb):
Definition:
Hemoglobin is an iron-containing red pigment present in RBCs that
carries oxygen and carbon dioxide.
Structure of Hemoglobin:
- It is a conjugated
protein.
- Made of:
- 4 Globin
chains (2 alpha, 2 beta)
- 4 Heme
groups (each has 1 iron molecule)
Mnemonic: “4G + 4H = 1 Hb”
Normal Hemoglobin Levels:
|
Group |
Hb Level |
|
Men |
13–18 g/dL |
|
Women |
12–16 g/dL |
|
Newborns |
14–20 g/dL |
Types of Hemoglobin:
|
Type |
Notes |
|
HbA |
Adult Hb (α2β2) – Most common type |
|
HbF |
Fetal Hb (α2γ2) – Higher O₂ affinity |
|
HbA2 |
Minor adult Hb (α2δ2) |
Mnemonic:
“A-F-A2” = Adult, Fetal, Adult Minor
A → α2β2
F → α2γ2
A2 → α2δ2
Functions of Hemoglobin:
|
Function |
Description |
|
O₂ Transport |
From lungs to tissues (as
oxyhemoglobin) |
|
CO₂ Transport |
From tissues to lungs (as
carbaminohemoglobin) |
|
Buffering Action |
Maintains blood pH |
Mnemonic: "HBO" =
Hemoglobin Buffers & carries O₂
2. Iron Metabolism
Daily Requirement of Iron:
|
Group |
Requirement |
|
Men |
~10 mg/day |
|
Women |
~18 mg/day |
|
Pregnant |
~30 mg/day |
Sources of Iron:
- Animal
source: Liver, red meat (heme iron – well absorbed)
- Plant
source: Green leafy vegetables (non-heme – less absorbed)
Mnemonic: “HeMaL” – Heme from Meat and Liver
Iron Absorption:
- Site: Duodenum
& upper jejunum
- Enhanced
by: Vitamin C, acidic pH
- Inhibited
by: Tea, phytates, calcium
Mnemonic:
“C helps C (Citrus helps Conversion)”
→ Vitamin C ↑ absorption
Transport of Iron:
- Iron is
transported in blood as Fe³⁺ bound to transferrin
Storage of Iron:
- Stored in
liver, spleen, bone marrow as:
- Ferritin
(soluble, major storage form)
- Hemosiderin
(insoluble, stored in overload)
Mnemonic: “Ferritin is Friendly, Hemosiderin is Hoarded”
Iron Cycle:
- Absorption in
duodenum
- Transport by
transferrin
- Uptake by bone
marrow → Hb synthesis
- Aging RBCs
destroyed → iron recycled
- Storage in
liver/spleen
Mnemonic: "ATUSS" → Absorb, Transport, Use,
Store, Scrap
3. Disorders Related to
Hemoglobin/Iron
|
Disorder |
Cause |
|
Anemia |
↓ Hb or ↓ iron |
|
Iron Deficiency |
Poor diet, blood loss |
|
Hemochromatosis |
Iron overload → organ damage |
|
Thalassemia |
Genetic defect in globin chain |
|
Sickle Cell Anemia |
Abnormal Hb → sickle-shaped RBCs |
Quick Comparison Table:
|
Feature |
Hemoglobin |
Iron Metabolism |
|
Main role |
O₂ transport |
Required for Hb synthesis |
|
Location |
Inside RBC |
Absorbed in gut, stored in liver |
|
Transport protein |
N/A |
Transferrin |
|
Storage form |
N/A |
Ferritin & Hemosiderin |
|
Daily requirement |
N/A |
10–30 mg depending on person |
FAQs – Frequently Asked Questions
Q1. What is the normal
level of hemoglobin?
Ans:
Men: 13–18 g/dL
Women: 12–16 g/dL
Q2. Where is iron absorbed
in the body?
Ans: Duodenum and upper jejunum
Q3. What enhances or
inhibits iron absorption?
Ans:
- Enhancers: Vitamin
C, acidic pH
- Inhibitors: Tea, calcium, phytates
Q4. What is ferritin?
Ans: Ferritin is the main storage form of iron in the body.
Q5. What is the role of
transferrin?
Ans: Transferrin transports iron in the blood.
Q6. What happens to
iron when RBCs are destroyed?
Ans: Iron is recycled and reused for new RBC formation.
