Why… is blood red?

The Week - Junior - - Science And Technology -

Ob­jects appear red be­cause they re­flect red light and ab­sorb other colours. Blood’s colour comes from the red blood cells it car­ries. These cells pick up oxy­gen from our lungs and carry it to where it is needed in the body. But why are they red in the first place?

Well, it’s all about our bod­ies’ chem­istry. Red blood cells have a pro­tein in them called haemoglobin that con­tains iron. When oxy­gen is bound to the iron, the haemoglobin re­flects red light, so the blood ap­pears bright red in colour. How­ever, when oxy­gen is re­leased, haemoglobin in­ter­acts with light slightly dif­fer­ently, mak­ing the blood now appear a much darker, ma­roon colour.

Email ques­tions to hello@the­weekju­nior.co.uk with the words SCIENCE QUES­TION in the sub­ject line. See more from Fran Scott in our 100-page spe­cial edi­tion, Science + Na­ture, the­weekju­nior.co.uk/science-na­ture

Name: Char­lie


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