Blue Is Pretty Special: How Nature Gets the Blues

this episode is sponsored by awesome socks club a sock subscription for charity click the link in the description and sign up between now and december 11th to get a fun pair of socks every month in 2021 [Music] the color blue is kind of special it has a reputation among biologists for being rare in nature except you've got birds insects flowers sea creatures even the eyes of some humans blue is everywhere so what's the deal well it is actually pretty hard for living things to make blue blue pigments at least many of the natural blues you see are really made using structural color microscopic structures that interfere with light to reflect color back to our eyes but blue pigments are a whole different game to make those life has to jump through some surprisingly big hoops pigments are molecules that selectively absorb and reflect visible light and they get their color from molecular structure and how the atoms are bonded to one another so to understand why natural blue pigments are so tricky we need to talk both biology and physics a lot of the problem with making blue pigment comes down to how molecules can have colors in the first place surprisingly complicated the very basic idea is that a molecule gets its color by reflecting and absorbing different kinds of light if it mostly reflects red it's red if it reflects everything it's white if it absorbs everything it's black but to understand the problem with natural blue you need to go a little deeper than that so imagine some generic molecule one with multiple atoms sharing some of their electrons in the form of chemical bonds those electrons usually exist in what's called a ground state with a set amount of energy and it tends to be as little as they can get away with but if you add some energy like if an electron absorbs a photon of light the electrons can jump to a higher so-called excited state that's pretty straightforward so far but one of the weird yet fundamental rules in physics is that electrons can only absorb light if it has exactly the right amount to actually get them to a new energy state if it's too much or too little the photon just bounces off the molecule it has to be just right and this is the reason why different things are different colors molecules have all kinds of different energy levels and photons of different colors of light have different amounts of energy shorter bluer wavelengths have the most energy while the longer redder wavelengths are like more laid back they're just chilling less energy low energy red so the shape of the molecule really matters because different structures within the molecule create those different energy levels if its electrons can only jump to an excited state with high energy light it's going to absorb blue and the opposite is true as well if it needs to absorb low energy light it will absorb reds and it turns out it is easier for life to make molecules that absorb blue and reflect red than the other way around blue rocks and minerals can hit that sweet spot thanks to either very complex crystal structures or the involvement of metals like copper and cobalt this works fine for us humans when we're making things like paints but metals like cobalt can wreak havoc in living things at high enough concentration so they're not necessarily something you want to like pack into your living cells so that you can have a nice bright blue color instead life is generally working with carbon as a starting material so to make an organic or carbon-based blue we need something that a living thing could both make and keep around without poisoning itself it turns out the kinds of carbon-based structures that lead to blue are often really complex but you can do it carbon specialty is joining up in long chains or rings and certain arrangements allow electrons to move throughout the chain this arrangement is known as a bond conjugation as the number of conjugated bonds gets higher the amount of energy between the molecules energy states decreases that means it takes less energy to boost the electrons into the excited state so the molecule will absorb lower energy red photons and reflect blue ones so the more conjugation you have the bluer the molecule appears the problem is the molecules that can accomplish this can be pretty tricky to use part of that may be that they're big and weirdly shaped but the relatively shorter gap between the electron states can also make it easier for these molecules to react with other molecules floating around which ruins all your lovely conjugation and destroys the pigment so blue pigments are hard but they are not impossible if you want to find one you can ask your liver about it after all there is one group of if not super blue at least blue-ish molecules that animals including us humans make and use on the regular they're called biliverdins and they're bluish green bile pigments bile pigments are a group of compounds that come in several types and are all made from the breakdown of certain other compounds often in the liver or spleen and bile pigments come in all sorts of colors including reds yellows and yes blues now biliverdins the blue ones never reach a real vibrant royal blue but they do give organisms some color like they're good enough to color birds eggs butterfly wings and some corals they're not normally used for their colorful properties and doing so might actually come at a cost scientists haven't really examined the connections here all that much at least when it comes to coloration but we do know at least in terms of health you might want to be careful when you're tweaking the bile pigment production pathway see biliveradine is often thought of as a waste product like other bile pigments but turns out it appears to also function as an antioxidant that's a molecule that can block other reactive molecules from damaging dna or other parts of the cell bilivaridin itself is usually turned into a yellow pigment called bilirubin which is an even more powerful antioxidant one that may have a role in protecting the cardiovascular system there's some evidence to show that giving up bilivaridin to color your body or shells could come at a cost to overall health researchers studying birds that make blue eggs have suggested that mothers with bluer eggshells make them by depleting their own biliverdin supplies giving up those valuable antioxidants now theoretically an animal that uses biliverdin for coloration could just like make extra but that would mean having extra bilirubin down the line and bilirubin can be toxic in large doses and then to get around that you could theoretically tamp down on the activity of the enzyme that changes bilivered into bilirubin but it turns out that that enzyme also helps control a lot of other important functions in cells so this part is a bit speculative but there might be some evolutionary pressure to just not mess around here so while some organisms do use biliverdin for its color like those butterflies and corals it doesn't seem like evolution has opted for it all that often again though we need more research to say that for sure and also know for sure why this is or isn't happening now this isn't the only pathway that can lead us to a blue pigment and for this next part we need to turn to our friends the plants plants can make a type of pigment called anthocyanins these are pigments found in blue flowers and they have enough conjugated bonds to do the job but they are unsurprisingly also super unstable in order to work they need very specific working environments ones that might be harmful for the cells as a whole like special acidities or the use of dangerous compounds so to keep them stable plants have to put them inside special compartments within the flower cells called vacuoles that way the plant can adjust the ph add metals or extra molecules or do whatever it needs to keep those blue pigments happy without applying those same tweaks to the whole cell unfortunately for any would-be painters that also means if you take the pigments out of the flower they tend to lose their color really fast but there are some solutions to the blue dilemma like chroma proteins these are proteins with color anthocyanins and biliveradines aren't proteins they're complex molecules but in the scheme of things relatively small proteins are made up of chains of amino acids and are much larger more complicated molecules than our other options but turns out they can be a good way for life to you know improve itself the most notable blue chromoprotein life makes may be hemocyanin the molecule that some invertebrates use to carry oxygen in their blood it's the equivalent of our red colored hemoglobin and the difference is partly thanks to metals hemocyanin has an atom of copper while hemoglobin uses iron horseshoe crabs for instance have hemocyanin in their blood and it is a beautiful baby blue color another example of a chroma protein is found in lobster shells lobsters get their dark bluish hue by taking two molecules of the normally red pigment astaxanthin and sticking them together they are then bound up in a protein to create beta-crustocyanin which is deposited in the lobster's exoskeleton protein parts form weak chemical bonds with the pigment which act kind of like conjugation and that they lower the energy needed for the electrons and the normally red astaxanthin to jump states that makes the complex blue fun fact this is also why lobsters turn red when you cook them the astaxanthin is freed from the protein as the protein part heats up and falls apart and voila you have a red shell crabs have a similar deal and other blue chromoproteins exist in some mollusks and jellyfish so while there are a few ways organisms have solved the blue pigment dilemma it ends up being a lot of hoops to jump through compare this to structural blues which are complex in their own right but often made of relatively easy to make building blocks like collagen so you don't have to use toxic substances nothing that could potentially interfere with the functioning of a cell to be clear here we're not saying organisms like considered their options and went with structures over pigments rather over the course of evolution they were just more likely to stumble on a blue structure rather than a blue pigment given all of the constraints on blue pigments which actually brings up a pretty decent question why go to the trouble of having pigments at all why do we have so many red and yellow pigments after all the molecules in structural colors are cheaper to make and more stable since they aren't absorbing light energy all the time this is literally why colors fade in sunlight the light energy molecules absorb can sometimes break them splitting the molecules apart or twisting them into new colorless forms so you also don't have to worry about structural colors fading but in a poetic turn of events while it's easy to make structural blue and hard to make chemical blue it turns out it's actually really hard to make structural reds you can get reds with iridescence where the color changes depending on the viewing angle think of a black bird's wing or an oyster's shell but it's much harder to create a pure red because blue light creeps in and pollutes it yellows and oranges are really hard too so blue is actually kind of special in that you can employ structural color to get vibrant blues so to recap it is hard for life to make blue pigments because it's hard for life to make the right kind of molecules they're often big or need a lot of help or require some cellular shenanigans to work right scientists are continuing to look for new blues of course we found a lot of exciting blues in the ocean for instance in the marine life not in the water to be clear like we know the water is blue that's structural actually not pigment and we're not going to open that whole can of worms because i think we already have an episode on it and finding and understanding these pigments could help us create better or more environmentally friendly paints and dyes but also it's amazing to look at the rainbow of colors life gives us and then be able to point to just one of them just the blues and say you know this one's special before we go i wanted to talk about the awesome socks club a thing that my brother john and i are starting which will definitely not give you the blues unless some of the socks are blue which i think that they will be this is your way to dress up your feet with 12 unique snazzy designs each created by a different designer every month of 2021 and 100 of after tax profits will go to decreased maternal and child mortality in sierra leone so your fancy feet will be helping other people too but the catch is you have to order by december 11th so we know how many socks to make so go to awesomesocks.club scishow to learn more [Music]

Channel: SciShow

Views: 334,024

Rating: 4.9511995 out of 5

Keywords: SciShow, science, Hank, Green, education, learn, Blue Is Pretty Special: How Nature Gets the Blues, biology, chemistry, biochemistry, organic chemistry, blue, structural color, pigments, physics, color, ground state, excited state, carbon-based, organic, bond conjugation, biliverdins, bile pigments, antioxidant, anthocyanin, vacuole, chromoprotiens, hemocyanin, astaxanthin, beta crustacyanin, collagen, iridescence, ocean, horseshoe crab, coral, robin eggs

Id: 9cdoPD51bng

Length: 12min 19sec (739 seconds)

Published: Wed Nov 25 2020