Why is blood red?

Why is blood red? 
In the mean time, let’s pay attention to the last slide I made (with a little bit of water). I was hoping to image some crawling neutrophils (cells responsible to fight foreign elements that invade our bodies). I setup a time lapse with a drop of blood. I did not notice any neutrophils as yet, but I was able to image flow of blood due to evaporation on the edges. 
I also got nice images of individual blood cells with 140x magnification lens. I like these images since they point to the absolute regularity of size in blood cells. It’s quiet remarkable how mono disperse blood cells are (if you measure each blood cell size in your body, they are all remarkably similar in same size). 

Now it makes me wonder, how large is the blood cell of a whale? Or of a chicken for that matter? We will find out next time I go to buy a chicken at a butcher or stumble across a carcass of a whale on a beach (probably not). 
Now – onto a question that I want to leave this post with; why is blood red? If you have red about it; the common answer is that the color is in the red blood cells. And that’s true off course, as is evident from the usual images of blood cells. But what I am puzzled with is this image below – which is a red drop but with no sight of red blood cells in it. So why is it red? 

 The answer might lie in the heme; the protein inside red blood cells that makes RBC red. I am wondering since that drop is red without any red blood cells; does it have some heme. So what happens to heme when blood cells burst out. I need to think more about this.. Try to see if you can crack this puzzle before me.



3 Comments Add yours

  1. Cristina says:

    Hi, Manu. I´ll try: If you added water to the drop of blood, red blood cells might have bursted in a less concentrated solution. Hence, haemoglobin, a water solluble protein responsible for the red colour of blood, is now colouring that water.

  2. Manu Prakash says:

    @Cristina: that is the most logical explanation j can think of. I will try to repeat this more carefully; with a control. Specially, if I can do this inside small droplets – I could truly see what is an effect of a few RBC bursting.

    Also; I did not see much ghost bodies of the burst RBC. Where did they go?


  3. laksiyer says:

    Manu, a parallel question, we know that the malarial parasite feeds on hemoglobin in the intra-RBC stage and converts it to a brownish hemozoin. if you do the same experiment on someone suffering from malaria, would we be able to see a slight shift in absorption peaks due to hemozoin and assay it at microvolumes? Perhaps it has been tried..

  4. Manu Prakash says:

    @Laks: That’s a brilliant suggestion. And it’s such a coincidence; I had a lab discussion at our last group meeting looking at role of Hb absorption and it’s drop in value in a single blood cell due to a malarial parasite.

    In cytometry, I did find several papers (most recent from an IISC lab, India) that has used this try to detect malaria. I see several challenges; but they are not unsurmountable – so I am indeed very excited about this.

    See review link below:

    From my experience in Nigeria, a big challenge is not to just tell is malaria is present; but also the fact which species it is. Secondly; cytometry misses out sickle cell and other mis-shaped RBC and other cells; which makes things very complicated.

    But if I think more about your suggestion; maybe it’s best to burst the cells inside droplets and use the droplets as a means for detecting the absorption level. I can see several advantages of the same.. I will try the emulsion assay and report back. Wound’t it be fun to solve a problem together – now I really want to setup the google forum. Very soon..


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