In the circulatory respiratory system, what protein carries oxygen and Co2? Where is that protein found?

Question

In the circulatory respiratory system, what protein carries oxygen and Co2? Where is that protein found?

Answer 1

I know that the hemoglobin in the blood is a kind of protein (actually, a metallo-protein) that carries O2.  I know it also has some other functions, so maybe it also carries CO2.

You could check hemoglobin in Wikipedia or something

Answer 2

hemoglobin and they are found within the blood of vertebrates.