Why does hydrogen peroxide bubble when it comes into contact with an owie? What do the bubbles accomplish? Why doesn’t it bubble when it touches ordinary skin? Why doesn’t it hurt as much as alchohol?
Hydrogen peroxide is H2O2. Enzymes (called peroxidases) that cause it to decompose into H2O (water) and O2 (gaseous oxygen) are found in many places (bacteria and horseradishes come to mind but evidently they are also found in owies). The bubbles don’t accomplish anything but they are formed from free oxygen which is highly reactive and kills bacteria. The bubbles are oxygen gas. Clean, ordinary skin doesn’t have much peroxidase. Alcohol hurts because it is toxic and kills unprotected tissue. Hydrogen peroxide hurts less because it is mainly active (and therefore toxic) where the peroxidase is which is usually dead tissue, especially infected dead tissue.
This is wrong. Peroxidases don’t produce molecular oxygen as a product. Enzymes that catalyze the breakdown of hydrogen peroxide into water and molecular oxygen are called catalases.
Despite what Yeah says, there is no more catalase or peroxidase in dead tissue than in healthy tissue. In tissue that’s been damaged, though, the catalase is more accessible to the hydrogen peroxide you put on it (because intact skin forms a barrier), so you get foam where there’s an injury but not on intact skin.
Thanks for the correction. I meant catalase, not peroxidase.
But Bob Scene didn’t understand the rest of the discussion. No one said or implied that there is more catalase or peroxidase in dead tissue than in healthy tissue. There was no discussion of injection of hydrogen peroxide INTO the skin. The question was about hydrogen peroxide in “contact with an owie” versus touching “ordinary skin” and my reply was about the relative lack of reaction when peroxide contacts “clean, ordinary skin.” It’s pretty clear that in the context of the response, “Clean, ordinary skin doesn’t have much [enzyme]” means “Clean, ordinary skin doesn’t have much [enzyme] on it.”
Pretty much what has already been said, but a little bit clearer:
thttp://www.howstuffworks.com/question115.htm
For your questions:
1.)catalase
2.)nothing
3.)Not much catalase on the surface of skin
4.)alcohol causes greater tissue damage because it is a superior solvent of lipids (the major component in cell membranes)
Fixed link:
“alcohol causes greater tissue damage because it is a superior solvent of lipids (the major component in cell membranes”
Is it really so simple? How about motor oil? Isn’t it a pretty good solvent of lipids? How come it doesn’t hurt as much as alcohol?
I don’t know how accurite this is but my High School Biology teacher mentioned that because H2O2 is produced during respiration, our cells have adapted to produces this catalase to break down the toxic stuff. Because bacteria and such don’t respirate like we do, they get killed by it.
Related question-- when we discussed this in college gen chem the prof mentioned that you only want to use H2O2 with a fresh wound as an initial cleansing and not as an ongoing treatment as it heals because the newly grown tender tissue is also damaged by its use. Comment?
Yeah, that is actually a very good question, but it has an answer.
The cell membrane is composed of a bilayer of lipids. The nonpolar carbon chains are oriented on the inside, and the polar phosphate groups are on the outside of the membrane. Picture two polywogs facing in opposite directions with their tails touching.
Non polar solvents (such as the alkanes in motor oil) cannot interract with the nonpolar tails of the lipids because those tails are protected by the outward facing polar phosphate groups. (remember, like dissolves like. Non-polar dissolves non-polar and polar dissolves polar).
Alchohol, however, is a polar solvent. Though it does not dissolve entire lipid molecules nearly as well as alkanes, it does something the alkanes can’t. It will “grab” the phosphate heads of the lipids and effectively rip the membrane apart. This lyses the cell, resulting in tissue damage. Tissue damage will cause pain.
capybara, your professor was right, though I wouldn’t worry too much about hydrogen peroxide. Hydrogen peroxide is only an antiseptic because it releases semi-toxic hydroxyl groups. In actuality, it’s really not a very effective antiseptic because your cells and invading bacteria aren’t harmed too badly by the hydroxide ions (though they sure don’t like them).
The fact is, any antiseptic, be it hydrogen peroxide, alchohol, iodine, or a nimber of others should not be used except in first aid. These chemicals do not discriminate between good cells and bad cells. They will kill the healing tissue the same as they kill the invading bacteria. Use them to clean the cut and “scorch the earth”, then let your immune system take over.
It is currently 10:40 PM and I have had a head start on tonight, waiting for others to get their shit together. Complaints regarding mispellings and incorrect grammar should be directed to the Anheiser Busch Corporation.
“alcohol causes greater tissue damage because it is a superior solvent of lipids (the major component in cell membranes”
“Though it [alcohol] does not dissolve entire lipid molecules nearly as well as alkanes…”
So what your saying is that your first post was actually incorrect. Alcohol does NOT cause greater tissue damage because it is a superior solvent of lipids. Alcohol causes much greater destruction of cell membranes because it is “is a polar solvent” and “It will ‘grab’ the phosphate heads of the [amphiphilic or ‘poliwog (sic)’-like] lipids and effectively rip the membrane apart.”
Water is also a polar solvent, a very good one, in fact. Bit it doesn’t cause much tissue destruction. There’s an answer to this one too.
We’re getting there.
yeah, I wasn’t wrong in my first post, alchohol is a superior solvent of lipids when compared to H[sub]2[/sub]O[sub]2[/sub], or water. H[sub]2[/sub]O[sub]2[/sub] is pretty much water. Water is only slightly polar, but alchohol is very polar due to the hydroxyl group that makes it an alchohol in the first place. Alchohol “grabs” the phosphate head of lipids far better than water.
Lord, it’s hard to explain the sollubility of water, but I’ll try. Water is the closest thing known to a “universal solvent”. This is because water is a simple molecule with two hydrogen oriented at an approximately 30 degree angle. This makes water only slightly polar. It is the shape of a boomerang with the ends the negative and the middle the positive. It is the closest thing I can think of that can do “double duty”. Dope it with a surfactant and you can dissolve nonpolar molecules (use dish detergent to take off burnt vegetable oil, etc).
However, alchohol is too damn polar, due to that -OH stuck on the end which makes it an alchohol, to do the same things that water does. In fact, that -OH group is far stickier than the slightly polar water boomerang and it will grab the phosphate groups readily, while water just skips off. My second post was meant to explain that structure and alignment is very important in organic chemistry; I’m not sure I did a good job. I’m trying to explain it here, but I’m not sure I’m doing a good job with this post either.
Again, all complaints should be directed to the Anheiser Busch Corporation.
Given alcohol is so ‘damn polar’, it’s interesting to note that it has a significantly lower boiling point (78°C at STP IIRC) than the ‘slightly polar’ water (100°C, STP).
How odd 
“Water is only slightly polar, but alchohol is very polar”
How do you measure polarity? Does it have anything to do with dipole moment?
IIRC, the dipole moment of water (g) is 1.85 x10exp18 esu, the dipole moment of ethanol (g) is 1.69 x 10exp 18 esu, and the dipole moment of methanol (g) is 1.7 x 10exp18.
Or were you thinking of a different alcohol?
Isopropil alcohol, maybe? But I do not know if it’s a different alcohol from methanol or ethanol, and what I remember from chemistry lab is that water is more polar than both of those alcohols.
PD. For me, at least, alcohol hurts less than hydrogen peroxide.
All I can add from my experience is that water is more polar than any alchohol I have had experience with. I think that water just skips off because it can’t do anything to disolve the long chain alkyl group of the lipid, whearas alchohols will have at least a short alkane chain to make the lipid happy. I’m guessing that the numbers for the dipole moment you obtained were for pure water at a pH of 7. Anything dissolved or a slight pH change will make water significantly more polar.
Beeblebrox- consumed internally, alchohol is not a very effective dissinfectant.
Solvent effects may explain why alcohol hurts more than water, but it has little to do with the difference between alcohol and peroxide. Rubbing alcohol is 70% isopropanol by weight, hydrogen peroxide is normally used as a 3% solution.
Even pure IPA hurts only a little more than rubbing alcohol; irrigating a wound with it for a long time would be a bad idea, but stronger solutions of peroxide will take your skin off.
10% peroxide causes chemical burns within minutes; 30% within seconds; the 50% solution I use for heavy metal digestions, I don’t want to think about