Hemoglobin And Plasma Proteins

HEMOGLOBIN AND PLASMA PROTEINS Hemoglobin: It consists of protein globin (polypeptide) and pigment haem. (heme). NORMAL VALUES: 1. At Birth: 24 gm% 2. At the end of 3 months: 10.5 gm% 3. After 3 months, increases and becomes 12.5 gm% at 1 year. 4. Adults: Males: 14-18 gm% Females: 12-15 gm% NOTE: 1 gm% of haemoglobin combines with 1.34 ml of oxygen when fully saturated. CATABOLISM OF HEMOGLOBIN Catabolism Old RBCs are destroyed in ‘tissue- macrophage system”. The system includes:

1) 2) 3) 4) 5) 6)

Kupffer cells of the liver. Alveolar macrophages in the lungs. Osteoclasts in the bone. Microglia in the brain. Lymph nodes. Spleen.

Note: 0.3 gm of hemoglobin is destroyed and 0.3 gm synthesized every hour.

Hemoglobin I Tissue macrophage system ↓SPLITS Globin (Enters amino acid pool)

Remaining part ↓ Biliverdin ↓(biliverdin reductase) BILIRUBIN

Haem (Iron protoporphyrin IX)

Fe2+ Combines with apoferritin ↓ FERRITIN (stored in the liver)

VARIANTS OF HEMOGLOBIN: 1) OXY HEMOGLOBIN: Hb reacts with O2 to form oxy Hb, HbO2. 2) CARBAMINO HEMOGLOBIN: CO2 reacts with Hb to form carbamino- Hb. 3) REDUCED HEMOGLOBIN: Hb from which oxygen has been removed is called reduced or deoxygenated hemoglobin. 4) CARBOXY HEMOGLOBIN: Carbon monoxide when reacts with hemoglobin, then it forms carboxy hemoglobin. The affinity of hemoglobin for CO is 250 times more than its affinity for oxygen. 5) METHAEMOGLOBIN: When reduced hemoglobin is exposed to oxidising agents, the ferrous (Fe2+) is oxidized to ferric (Fe3+) form and the compound is called methemoglobin; HbOH. 1. It is dark colored, when present in large amounts in circulation (1.5gm %), it mimics cyanosis. 2. It cannot unite reversibly with gaseous oxygen.

FUNCTIONS OF HEMOGLOBIN 1. Oxygen transport from lungs to tissues. 2. CO2 transport from tissues to lungs. 3. Acts as acid –base buffer. 4. It promotes vasodilation in the tissues.

VARIETIES OF HAEMOGLOBIN: 1. ADULT HAEMOGLOBIN: (HbA) Two types: Hb A (α2β2) Hb A2 (α2δ2) Hb A appears in fetus 5 months of intra-uterine life.

Amount of Hb A of total Hb. AT BIRTH 20% (rest is Hb F) AT 2 MONTHS 50% AT 4 MONTHS 90% MORE THAN 1 YEAR. >99% (1% is Hb F) 2.

FETAL HEMOGLOBIN (Hb F) 1. Structure is similar to Hb A, but beta chains are replaced by gamma chains. 2. More resistant to the action of alkalies than HbA. 3. HbF has higher affinity for oxygen due to weak binding to 2,3-DPG. Thereby facilitating the movement of oxygen from maternal to fetal circulation. 4. It can take up larger volume of oxygen than HbA at lower oxygen pressure. At 20 mm Hg pressure , Hb F 70% saturated Hb A 30% saturated

3. Life span of Hb A is 80 days as compared to 120 days of HbA. 4. At Birth, Hb F predominates, that disappears 3 months after birth.

2. HbS Beta globin chain of HbA at position 6, one glutamic acid is replaced with valine. When HbS is reduced, it becomes less soluble than HbA, and precipitates into crystals within RBC. Further it can cause > Damage of the cell membranes. >Crystals elongate and RBCs become sickle shaped RBCs become more fragile, producing severe anemia, called sickle cell anemia.

Plasma proteins: Total plasma protein concentration: 6.5 -8.2 gm/ 100 ml of blood. PLASMA PROTEINS: 55%

38% 7%

1. PRE- ALBUMIN 0.03gm% Binds T3 and T4. 2. ALBUMIN. 3.4-5.5 gm% • Controls colloidal osmotic pressure. • Role in transport of anions, cations, drugs, hormones, amino acids, enzymes and bilirubin. 3. GLOBULIN 2-3gm% 4. FIBRINOGEN 0.3 gm% Helps in blood coagulation. 5. PROTHROMBIN 40 mg% Helps in blood coagulation.

Albumin: Globulin : A/G 1.7: 1. Varoius forms of Globulins in body are 1. Glycoprotein. 2. Lipoprotein. 3. Transferrin 4. Haptoglobins 5. Ceruloplasmin. 6. Coagulation factors 7. Angiotensinogen 8. Haemagglutinins 9. Immunoglobulin

FUNCTIONS OF PLASMA PROTEINS 1. Important role in blood coagulation. 2. Maintain colloidal osmotic pressure (COP). 3. Maintain viscosity of blood. 4. Maintain systemic arterial blood pressure constant. 5. Provides stability to blood. 6. Maintains acid base balance in blood. 7. Immune function. 8. Transport function. 9. Reservoir function. 10. Nutrition of tissues.