hemoglobinstructuresynthesisbreakdown-220418045309.pdf
- 2. Haemoglobin: •Haemoglobin is a type of globular protein present in red blood cells (RBCs), which transports oxygen in our body through blood. It is a tetrameric protein and contains the heme prosthetic group attached to each subunit. •It is a respiratory pigment and helps in transporting oxygen as oxyhaemoglobin from the lungs to different parts of the body. Some amount of carbon dioxide is also transported back via haemoglobin as carbaminohaemoglobin.
- 3. Haemoglobin: •The haemoglobin level is measured in g/dL of the blood. In a healthy individual, the level ranges from 12 to 20 g/dL. Generally Hb level in males is greater compared to females. •The normal level in Males is 13.5 to 17.5 g/dL and in Females, it is 12 to 15.5 g/dL.
- 4. Haemoglobin Structure: Max Perutz described the molecular structure of haemoglobin in 1959. Haemoglobin is a tetrameric protein. The main type of haemoglobin in adults is made up of two subunits each of ‘ 𝜶’ and ‘𝝱’ polypeptide chains. Each polypeptide chain is linked to a heme prosthetic group. •𝜶 subunit – It is made up of alpha polypeptide chain having 141 amino acid residues. •𝝱 subunit – It is made up of beta polypeptide chain having 146 amino acid residues. •Heme group – It is an iron-containing prosthetic group, which is attached to each polypeptide chain. It contains iron in the centre of the porphyrin ring.
- 5. Haemoglobin Structure: • Hemoglobin is a protein ( Heme+protein ) • Types of proteins are globular proteins ( functional proteins ) linear proteins ( structural proteins ) There are four iron atoms in each molecule of hemoglobin, which, accordingly, can bind four atoms of oxygen. • Hb is considered of globular proteins. • Mature RBCs do NOT synthesis Hb, while immature RBCs synthesis Hb. • Mitochondria is very important for Heme synthesis
- 6. Hemoglobin = Heme + globin ( protein ) Note : globin is considered as a protein so that it synthesized by RER.
- 8. Each hemoglobin molecule ( Globular protein ) consists of 1. 4 Heme 2. 4 linear proteins each one bind to a Heme
- 9. Heme synthesis • Heme = Protoporphyrin + Iron • Protoporphyrin = Iron free Heme • Protoporphyrin consist of 4 pyrrol rings. • Iron have 6 coordination, 4 bind with these 4 pyrrol rings of protoporphyrin, 1 bind with histidine ( amino acid ) from globulin and 1 is free (bind to Oxygen , CO2 respectively)
- 11. Iron in Hemoglobin is ferrous or ferric ? Why ? • Iron in ferrous form ( 6 coordination ) 1) 4 bind with protoporphyrin 2) 1 bind to histidine ( globin ) 3) 1 free bind to O2 or CO2 respectively • Where in ferric form we well have one bond missing ( malfunctional hemoglobin ) • Heme and globulin are not isolated, they bind together by Iron,
- 12. Types of Hemoglobin Normal • Different types of Hb due to different type of globin NOT Heme. and small amount of • Adult have HbA HbA2. • Fetus Have HbF.
- 13. Types of Hemoglobin Type Formula HbA (95-98%) α2β2 HbA2 (2-3%) α2δ2 HbF (upto 2.5%) α2γ2 HbF have more affinity to oxygen than HbA.
- 14. Gas Transportation • Why we use hemoglobin as a transporter for oxygen ? 1. Because of low solubility of oxygen in water. 2. Hemoglobin have a regulatory effect on oxygen concentration in lungs and tissues. Note : all tissue required of oxygen and 20% of CO2 from metabolic wastes transport via Hb.
- 15. Allosteric effect • When an enzyme reacts to effectors with conformational changes that increase or reduce its activity, it is said to show allosteric behavior • Many substances act on Hb as an allosteric substances. • Although Hb is NOT an enzyme, but it have all the characteristics of enzymes
- 16. • Substances that have an allosteric effect on Hb are : 1. 2,3 DPG (Intermediate factor in glycolysis) 2. H+ ( i.e. ph effect on Hb ) 3. CO2
- 17. Forms of Hb • When Hb have high affinity to oxygen in lung is called ( oxyhemoglobin ) and refereed to as R form ( R from Relax )
- 18. • When Hb have low affinity to oxygen in tissue is called ( deoxyhemoglobin ) and refereed to as T form ( T from Tense )
- 19. Steps for O2- CO2 Transport 1. In lungs, Pressure of oxygen is high so it diffuse from outside the body to inside the body and bind with Hb. (bond of one O2 to hemoglobin facilitate the binding of other O2 molecule). 2. In tissues, hemoglobin bind to 2,3 DPG and that cause to decrease affinity of Hb to Oxygen and releasing Oxygen to the tissues.