The colors of blood

[Broomstick]

What colors does blood come in?

Yes, we all know vertebrates bleed red, being such ourselves. And it’s red due to hemoglobin, a molecule containing iron.

But I seem to recall hearing that blood also comes in blue in some arthropods like horseshoe crabs and crustations? I don’t spend a lot of time inflicting harm on other creatures so I don’t recall seeing this. What would make it blue?

And I also recall reading something about yellow in insects? About the only things I squash on a regular basis is mosquitoes which, having usually just sucked my blood, tend to leave red smears. If it is yellow - why?

And are there any other colors that blood comes in?

[KarlGrenze]

Maybe it is blue in mollusks because they don’t use hemoglobin, but another protein copper-based instead of iron-based. That protein is less effective in transporting oxygen than hemoglobin. I’m probably wrong, but that is the only difference I know.

Insects have an open circulatory system, meaning their blood mixes with the bodily fluids and is called hemolymph. I think they also don’t have hemoglobin…maybe that is the reason their blood is not red?

[Tamerlane]

*Originally posted by KarlGrenze *
**Maybe it is blue in mollusks because they don’t use hemoglobin, but another protein copper-based instead of iron-based. That protein is less effective in transporting oxygen than hemoglobin. I’m probably wrong, but that is the only difference I know.

Hemocyanin . There do seem to be advantages to using hemocyanin under certain conditions - see link below.

Broomstick: Here’s an old thread where we went into some detail on this ( though if an expert wanders by, we could probably always do with a little more ).

http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=69786

• Tamerlane

[David_Simmons]

*Originally posted by Broomstick *
**What colors does blood come in?

Yes, we all know vertebrates bleed red, being such ourselves. And it’s red due to hemoglobin, a molecule containing iron.

**

Venous blood also contains hemoglobin and it’s blue. Arterial blood is red because the hemoglobin has picked up oxygen.

[Whack-a-Mole]

*Originally posted by David Simmons *Venous blood also contains hemoglobin and it’s blue. Arterial blood is red because the hemoglobin has picked up oxygen. **

Yup…just look at your arm and you can see your blue/green veins.

The reason you never see blue blood is that when you bleed the blood is exposed to oxygen which it grabs and so appears red.

[Thing_1]

                                    quote:

                                    Originally posted by David Simmons Venous blood also contains
                                    hemoglobin and it's blue. Arterial blood is red because the hemoglobin
                                    has picked up oxygen. **


                              Yup...just look at your arm and you can see your blue/green veins. 

                              The reason you never see blue blood is that when you bleed the blood is exposed to
                              oxygen which it grabs and so appears red.

Venous blood is not really blue. Have you never seen blood drawn into an empty syringe or vacutainer tube (no O2)? It comes out rather a maroon color. Maybe with a slightly purple hue, but definitely not blue. But I guess it depends on your definition of blue.

John

[AndrewL]

Our blood is not blue under any conditions. It’s not even purple. Our blood goes from dull reddish brown when poorly oxygenated, to bright red when well oxygenated. The bluish appearance of veins is an optical illusion.

[Bromley]

To follow up what Andrew just said, this post explains what the illusion is.

Jay Walsh manages to lose me in parts, but basically the red light is absorbed and only the blue is “remitted” (or something like that ).