Hemoglobin

Lectured by: Dr. Aniruddha; Management & Science University
Notes by: Malilith F. Ila; from Dr. Aniruddha's class lecture

Or also known as haemoglobin


Functions of haemoglobin
i) Delivers oxygen to tissues
ii) Take carbon dioxide to the lungs
iii) For gas exchange process

- One hemoglobin can bind to 4 oxygen molecules
- Less than 0.01second required for oxygen binding
- β-chain move closer when it is oxygenated
- When oxygenated, 2-3-DPG (2-3-diphosphoglycerate) is pushed out
- β-chains are pushed apart when oxygen is unloaded, permitting entry

Hemoglobin must bind to the oxygen in the lungs and release it in the capillaries
- When the first Fe in heme in hemoglobin binds to oxygen, the Fe, heme, is drawn into the base of porphyrin ring
- This initiates a series of conformational changes that are transmitted to adjacent subunits
- Adjacent subunits affinity for oxygen increases
- This is called as a positive cooperativity



Extra! Venous blood = 20-60mmHg of oxygen; Arterial blood = 60-80mmHg of oxygen





When blood is in the lungs, where the oxygen is plenty, oxygen easily binds to the first subunits and then quickly fills up the remainings.
Then, as blood circulated through the body, the oxygen level drops while that of carbon dioxide increases

Hemoglobin releases its oxygen, as soon as the 1st oxygen molecule drops off, the protein starts changing its shape
- This prompts the remaining three oxygen to be quickly released
- In this way, hemoglobin picks up the largest load of oxygen in lungs, and deliver to where and when it's needed





Extra! Addition of carbon dioxide decreases the affinity of oxygen





Hemoglobin-oxygen dissociation curve


- Oxygen carrying capacity of hemoglobin at different concentration of oxygen
- Sigmoid shaped
- Binding of one molecule facilitate the second molecule binding





Extra! P50 is the partial pressure of O2 at which hemoglobin is half saturated with oxygen; 26.6 mmHg





Fate of Red Blood Cells

- Erythrocytes only stay in the circulation for about 120 days
- Then, it was engulfed by macrophages by phagocytosis (the old and damaged erythrocytes)






Extra! Conjugated bilirubin is not soluble in water. Also called as indirect bilirubin. Unconjugated bilirubin is soluble in water and can be excreted through urine. Also called as direct bilirubin.





Reference;
http://www.csun.edu/~jm77307/Hemoglobin.pdf
http://www.austincc.edu/~emeyerth/hemoglob.htm
http://www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2005/Heiner/hemoglobin.html
http://en.wikipedia.org/wiki/Hemoglobin
http://www.ncbi.nlm.nih.gov/pubmed/7555018
http://en.wikipedia.org/wiki/Oxygen%E2%80%93haemoglobin_dissociation_curve
http://en.wikipedia.org/wiki/Urobilinogen
http://en.wikipedia.org/wiki/Stercobilin
http://en.wikipedia.org/wiki/Stercobilinogen
http://www.rnceus.com/lf/lfbili.html
http://www.tikirobot.net/wp/wp-content/uploads/2007/11/0143.gif