Is blood actually blue?

[Squintz]

Is blood really blue when its inside your body? What causes it to turn red?

[atinymonkey]

:giggle: that's silly.

[Squintz]

I thought so also, but i remember as a kid being told that blood is blue until it hits the air and then it turns red.

[Sayonara]

Deoxygenated blood in your veins is more blue than the highly-oxygenated blood in your arteries.

[Squintz]

I think i answered my own question. Blood is never blue but appears to be blue when viewed *through* skin. Because it does not reflect light bery well? Blood is Actually dark red!

[Sayonara]

Vulcans have green blood and Klingons have pink blood.

 

Except on Voyager, where everyone has red blood because they're all human at heart.

 

 

Just thought I'd mention it.

[fafalone]

Your blood is never blue.

 

Ever.

 

Your veins appear blue through the skin, but if you have a green hose does that mean the water is green?

 

...and furthermore blood derives its color from hemoglobin, not oxygen. Deoxygenated blood has the same color as oxygenated blood.

[Sayonara]

I was under the impression that oxygen-haemoglobin complex is a different colour to haemoglobin on its own, despite the presence of iron. However it does make more sense that this colour comes from the lining of the minor vessels rather than the blood itself.

Any sources?

 

ps - note how I said "more", as opposed to de facto.

 

[Edit]

 

Also, I just recalled that carbon monoxide binds with haemoglobin to form a complex that has a very bright red colour. If that complex can change the reflected wavelengths of haemoglobin, why can't the oxygen-haemoglobin complex be a different colour to haemoglobin on its own? Anyone?

[atinymonkey]

:giggle: hemoglobin, haemoglobin. Potato, Plato.

[VendingMenace]

Deoxygenated blood has the same color as oxygenated blood.

 

I think i will have to disagree with you here. The iron that is at the center of the porphrin found in hemoglobin is in different oxidation states when it is oxygenated and when it is not oxygenated. As a direct result the MLCT (metal to ligand charge transfer) bands are different in the two states. It is the MLCT electronic transitions that give metal complexes their color. Thus, it the oxygenated and non-oxygentated complexes do have different colors.

 

Now as far as red and blue goes...i am not quite sure, but i think that it is true. If memory serves the non-oxygenated iron is blue, but of course when you see blood, there are othing things to be seen, that can makes things look not quite blue. And of course we are chemists here so remember we do not mean crayola blue, just that it looks blue. I will try to find where i read this specifically for hemeoglobin, but i do belive that it is red/blue depending on the oxidation state.

[fafalone]

I'll have to disagree with that. Oxygen does not bond to the iron, and its oxidation state is not changed. Oxygen binding is coupled to a movement of beta chains, and I believe the bonding occurs with carboxyl groups on the outsides of each of the 4 subunits. The iron atom is surrounded by these subunits, and does not change. Deoxygenation will result in a color change (but nothing even close to blue, just different shades of red), but I do not believe it's related to the oxidation state of the central iron.

[Kedas]

I think I will have to disagree with both of you:

Question: Is blood still red when you are colour blind ???

(even when you don't have iron because your mam is using it)

[fafalone]

Red is defined as a certain wavelength range of light in the electromagnetic spectrum, so yes its red regardless if you can perceive it as that or not.

[Kedas]

LOL @ fafalone (You took that question serious.)

It's actually a philosophical question.

[Skye]

Oxygen is a ligand to iron in a heme complex in hemoglobin. The other 5 (iron has a coordination number of 6) ligands are nitrogens, four from a porphyrin molecule and one from one of the subunits. This forms oxyhemoglobin, which is bright red. Water binds in oxygens place if there's no oxygen which is called deoxyhemoglobin, which is more of a crimson colour. CO binds preferentially with the complex and displaces oxygen, and is a brighter red.

[VendingMenace]

Oxygen binding is coupled to a movement of beta chains

 

right. oxygen binding causes a change in the tertiary structure of the protein. What you are reffering to, i believe, is the so called "cooperation effect." However, the advent of this structureal change is brought about by the binding of oxygen, it is not the reason oxygen binds. At least that is what i heard last.

 

and I believe the bonding occurs with carboxyl groups on the outsides of each of the 4 subunits.

 

This can't be. How would oxygen bind to a carboxyl group? First you would end up with a -O-O-O motif then, and you would observe ozone evolving. HOwever, this clearely does not happen.

 

Ozygen binds to the iron in the heme complex. It is this iron that is the carrier for both O2 and CO2.

 

 

Water binds in oxygens place if there's no oxygen which is called deoxyhemoglobin

 

yeah, but what happens when it is carrying a CO2?

[Skye]

I don't think the CO2 acts as a ligand with iron, but it does directly bond with the amino acids in hemoglobin to form 'carbamino' groups. Deoxyhemoglobin has a greater affinity for CO2 to produce carbamino groups. I don't know how this affects the colour of the hemoglobin, but probably not very important compared to the porphyrin which is a coordination compound.

 

However, the main way CO2 is transported by blood is as the more soluable HCO2-, which is enzymatically hydrated with H+ ions as a by-product.

 

H20 + CO2 --> HCO2- + H+

 

The H+ ions change the shape of hemoglobin so it carries less oxygen and in this way changes the colour of blood.

[Glider]

Skye is right. Oxyhaemoglobin - deoxyhaemoglobin - carboxyhaemoglobin.

 

In any event, if you want to know about the different colours of blood, ask a phlebotomist

I have bled thousands of people, and I can vouch for the fact that venous blood is extremely dark purple. If you allow air to get to it (or spill it), you can watch it change colour to a bright poppy red in a few seconds. If it's bright red when it enters the syringe, it's arterial, and you have a problem (unless it was deliberate, as in an arterial stab for blood gasses).

[Sayonara]

We all know that blood is not coloured blue as in 0000FF, but that's not where I was going in reply #4. You can tell that by my cunning use of the words that said what I meant.

 

My thinking was that if it were possible to show that venous blood is more blue than arterial blood (EG FF001A compared to FF0000) then this might explain how the original question came about.

 

Some people (mentioning no names) are far too obsessed with proving others "wrong".

[Glider]

I agree, though there is a degree of subjectivity involved, I would have to say that venous blood is more blue than red (i.e. if you were to mix blue and red to get the purple of venous blood, it would take more blue than red).

 

If you look at somebody who is cyanotic, they have a general blue tinge and bright blue lips too.

[Pinch Paxton]

Syringes don't contain air do they? So syringed blood is the true colour of blood inside the body. Syringed blood is dark red.

 

Pincho.

[Glider]

Syringes do contain air. You can see the bubble when you draw a sample. Syringes designed to take arterial blood-gas samples have a plunger which is designed to eliminate that air bubble (which is enough to change the sats values significantly). The plunger has a projection which fits into the leur cone, eliminating that space. Normal syringes don't have this.

 

The best way to see the colour of venous blood is to take the sample directly into an oxygen free container, e.g. an anaerobic blood culture sample.

[Sayonara]

Saying "syringed blood is dark red" doesn't help anyone if you can't provide a reason - in terms of colour - why "dark red" is different to "red".

[VendingMenace]

right, if you want a hard core explination as to why, then i would suggest doing some reading up on "weak feild and strong feild ligands" also doing a searh for "spectrochemical series" would give you some information too.

 

Basically though, the take home message is that different ligands bound to a metal center influence the splitting of the moliecular orbitals of the metal complex. Because of this the energy differences between what are called "states" in the metal complex change due to what is bound. IN many cases these states even swap relative positions, on an energy diagram. Now a molecule is usually assumed to lie in the ground state of a molecule, and when light shines on it, you can excite it to a new state. When this excited state relaxes back to the ground state it releases a photon of the apporpriate energy. By binding different ligands to a metal we can tune what the energy difference is between the ground and lowest allowed excited state. By doing this, we are also tuning what energy of photon is released upon relaxation back to the ground state. Of course the energy of the light is dependent on its wavelength, and hence its color. Thus, the binding of two different ligands to the same metal center will cause different colors in that complex.

 

IN order to determine what the colors will be, one need either look at the complex and observe it color (as glider does) or site down and rigourously calculate it (using a comp, unlless you feel like sacrificing a day or so).

 

Yeah, so it is the various ligands that influence the energy ordering of states within the molecule. This theory is known as ligand feild theory, or crystal feild theory (crystal feild theory makes many more simplyfing assumptions than does ligand feild theory).

[Pinch Paxton]

Saying "syringed blood is dark red" doesn't help anyone if you can't provide a reason - in terms of colour - why "dark red" is different to "red".

 

It's a good enough answer being as the question was.."Is Blood blue?"

 

Pincho.