Chris -   Can chlorophyll actually be introduced into our bodies so that we could avoid hunger for example?  So when you get peckish, rather than have to eat something, you just go and bask in the sunshine (assuming you don't live in Britain where there is no sun!)

Dave -   I thought I’d start off with a physics approach to this to see whether it’s at all practical.  You’ve got about half a square metre of skin which you can point at the sun (you’ve got about a square metre in total, but you can only point half of it at the sun at any one time).  The sun produces, at most if you're on the equator and on a really sunny day at midday,  about a kilowatt of sunlight per square meter.  It’s probably about half that on average during the day and it's only day time half the time – so on average over 24 hours about 250 Watts.  The maximum theoretical efficiency of photosynthesis is about 20%.  But that’s only compared to the half of the light it can absorb, so that’s only about 10% efficiency.  If you multiply those all up, you get about 12 Watts of power continuously throughout the day if your skin was completely saturated with chlorophyll, in practice the output would probably be far less than this.  Now it sounds like that might be quite useful but the problem is that when you're just sitting in a chair, vegging, you use about 60 watts of power.

So, it might help a little bit, but no it certainly won't solve all your problems.  I'm also guessing that the actual physiological issues would be quite serious.  I guess Chris you’re better to talk about those!

Chris -   Well some animals have done this to a great effect.  There’s the Sacoglossan sea slug which famously in recent years has been discovered to actually have chloroplasts – chlorophyll containing bodies - in its skin.  This slug eats algae, marine microorganisms including sea weeds and things, and it has got this special system where it has tubes connecting the lining of its gut with its skin.  When it eats the algae, it gets the chloroplasts with the chlorophyll in from the algae and puts them under its skin.  Amazingly, the genome of the sea slug contains a number of additional genes from sea weed that can keep those chloroplasts alive.  So this sea slug really does augment its metabolism using sunlight.

Presumably, your worry would be if you start putting chlorophyll into the body, would the immune system have something to say about it?  The likelihood is, if you got it in there from birth, so you educated the immune system about it, I don't think there’d be a problem.  Let’s face it, if you're in a position to start turning people green, the likelihood is that you probably would’ve surmounted the immune problem too, I would guess!

Dave -   I guess you’d need some quite serious genetic engineering to be able to add those genes into your body to be able to support the chloroplasts as well...

Dave -  I had a go at this doing chromatography on chlorophyll on Kitchen Science a few weeks ago.  Although most of the pigment in the plant is actually purple, if you actually do the chromatography, you do see there is still some green pigment in there, and so there is some green chlorophyll there in purple plants to do the photosyntesising, they just have other pigments as well which absorb green and yellow light to make them a deep purple colour.

In things like algae and sea weeds, they canhave a different colour of chlorophyll, a completely different chlorophyll which absorbs blue light better than red light, because blue light travels through water a lot better than red light.

Chris -   Yes, red light doesn’t - that’s why blood looks black under water because all the red light has been soaked up by the upper layers of water.

Dave -   Yes.

Chris -   And there’s nothing to reflect off the red blood, so it looks black.

Dave -   So red sea weeds have just got a different form of chlorophyll and I think that purple plants just have some green chlorophyll in there as well as a purple pigment which doesn't photosynthesise.

Kat -  In fact, they have.  Craig Venter, the US Genome Sequencing bod, publisheda report in the journal Science a couple of years ago - they did actually completely build a very simple bacterium, Mycoplasma genitalium from scratch.  They made all the DNA and they kind of put it all together.  It was incredibly hard to do.  The fact that we know the genome sequence of a lot of organisms and particularly simple organisms like viruses and bacteria is a far cry from actually making the DNA in exactly the right order, building that DNA strand and then putting the whole thing together.  But I think Craig Venter’s grand plan is to make artificial life.  This is certainly a start and it has kind of been done.  So, yes - it has been done, but it’s very difficult.

Chris -   But the cynics would say that he used a cell that had already been made and then put the genetic material in and it’s that key thing is that membrane being made, it’s the biochemistry that kick starts the DNA you put in into action which is the key recipe, the key ingredient in life that we just don't understand at the moment.

Kat -   That’s true and some people did say, "you've just stuck an instruction book into this bag of stuff!"  I think building the rest of it is going to prove more tricky.  The fact that we know what makes it up doesn’t prove that we know how it’s been put together.  But obviously, the more we understand about how enzymes work, how organisms work, it might be possible.  In terms of creating life from scratch, there were the famous experiments by Stanley Miller in the 1950s and ‘70s, mixing together a whole bunch of chemicals, zapping it with electricity and making things like simple amino acids.  So those kind of experiments are being done as well.  So, it may be that we will see completely artificial life appearing in the lab soon.

It’s nature’s example of Joseph and his Technicolour Dream Coat, the chameleon.  They're just phenomenal. 

There is this myth that chameleons change colour to blend in with their surroundings, but this is actually not true.  Most of the reason chameleons change colour is as a signal, a visual signal of mood and aggression, territory and mating behaviour.

The way that chameleons actually do this is really molecular – they're molecular masterminds, really.  If you look at the skin of a chameleon, you find that they have several layers of specialised cells called chromatophores and these are cells that can change colour.  On the outer surface of the chameleon, the skin is transparent and just below that is the first layer of these cells, and they contain various pigments.  These are xanthophores, containing particular specialised pigments that have a yellow colour.  Beneath that are pigment cells which are called erythrophores which have a red colour in them.  Beneath that, another layer of cells called iridiphores have a blue coloured pigment called guanine, which is actually also used in making DNA.  And underneath that is another layer of cells called melanophores which have a brown pigment – melanin – in them. 

Now, how does the chameleon change colour?  Well those chromatophores are wired up to the nervous system.  They are also sensitive to chemicals that are washing around in the blood stream of the chameleon.  What happens is that the colours are locked away in tiny vesicles, little sacs inside the cells that keep them in one place, so the cells don't look coloured.  But when a signal comes in from the nervous system or from the blood stream, the granules or vesicles can discharge, allowing the colour to spread out across the cell, and this alters the colour of the cell.  It’s rather like giving the cell a coat of paint.  By varying the relative amount of activity of the different chromatophores in different layers of the skin, it’s like mixing different paints together.  So if you mix red and yellow, you get orange for example, and this is how chameleons do this.  They mix different contributions of these chromatophores.  It’s a bit like on your television screen.  When you mix different colours together on the screen to get the colour that the eye ultimately perceives and so, that’s how the chameleon changes colour, and usually does so to convey mood.

So a calm chameleon is a pale greeny colour.  When it gets angry, it might go bright yellow, and when it wants to mate, it basically turns on every possible colour it can which shows that it’s in the mood.  This is not unique to chameleons.  Other animals also have these chromatophores. Cuttlefish are another very elegant example of how this works.  So it’s not so much to do with camouflage.  It’s more to do with communication.

Dave -  Lightning is basically a huge spark.  You get about 100,000 Amps of current flowing down through the air.  This gives out about a thousand trillion Watts for about 30 millionths of a second, so the total amount of energy released is about 30 mega Joules of energy.  That’s very roughly similar to a 30-kilogram bomb.

Chris -   It depends on what the bomb is made of, doesn’t it?

Dave -   Yes, but it’s similar of order of magnitude.  Quite a lot of that energy is going to be a long way up into the sky though.  So basically, that energy is equivalent of about a kilogram of, say, TNT going off near your house.  Most of that energy goes into heating up the air and it gets very, very hot.  When hot air expands, that creates a shockwave of air pushing outwards and that’s what you hear as a thunder.  If that happens very, very close to you, then you will actually get quite a large overpressure, like a bomb going off, and if a bomb can shake your house, then a lightning strike should be able to.

Chris -   I did some back of the envelope calculations.  I think it’s 120,000 pieces of toast you could make with the energy in one lightning bolt, assuming you could turn all of it into toast, obviously.  So that’s really quite a lot, isn’t it?

Dave -   For the time period, certainly, yes.

Kat - I think he’s little bird brained!  Now, birds do fly into windows.  At home, my Mum has a lot of bird outlines stuck against the window to stop them flying into them. They fly into them for various reasons.  Firstly, it’s clear glass - they might not see it’s there.  They might think, “Ooh! That looks like a nice room, maybe a bit of floral wallpaper...”  Bang! Straight into the window.  So if you do have big patio doors, it’s quite good to put stickers or something on them. 

The other thing is that the birds may be seeing their own reflection and, as it is the time of year when birds maybe get a little bit frisky, they start fighting with each other.  Maybe it’s a male bird, and it will start fighting with male birds or trying to mate with lady birds.  So perhaps...

Chris -   Surely they should mate with feathered birds because lady birds are insects and are a bit small for a bird to mate with, aren’t they?

Kat -   Female birds.  Thank you, Chris. 

So perhaps the bird is actually seeing its reflection in the glass and flying at it, trying to attack it and not realising that it’s not another bird, it’s its own reflection.  Especially with houses normally if the room behind it is quite dark, that makes the window look even more reflective and then act more like a mirror.  So I suspect that your bird is fighting some imaginary turf war with itself and that’s why it keeps flying into your window.  Try keeping the lights on in the room so that the room’s not so dark or try getting a cat or putting something like stickers or something on the window might help.

Chris -   Or a shotgun of course.

Kat -   Or a shotgun.  No!  That would be nasty.

Chris -   I can deal with the spicy one straight away because in fact, that’s a myth and there’s evidence that people who eat a lot of spicy food have lower rates of Alzheimer's disease than people who don't eat spicy food.  This is because turmeric, the orange stuff which, when you get a bit drunk in the curry house and spill your curry down your shirt (which is always white for some reason when this happens), is the stuff that stains.  Turmeric has actually got anti-inflammatory and anti-oxidant qualities.  It seems to cut down the production in the brain of a chemical called beta amyloid and beta amyloid is the stuff that makes Alzheimer's disease happen.  It builds up and forms plaques in the brain that damage nerve cells.  So if you eat lots of turmeric, it seems to reduce the risk of that happening.  So spicy food is good for your brain. 

That’s that one done.  Booze – booze is more difficult.  The evidence is, if you were to incubate nerve cells in a solution of alcohol, they would die.  So alcohol is a toxin.  Thankfully, the body is really well set up to deal with it metabolically.  The liver handles alcohol extremely well and only a tiny proportion of the alcohol we drink actually gets into circulation because the liver sees all of the blood that comes from the digestive tract before it goes anywhere near the rest of your body, and the liver therefore deals with the booze before it goes systemically around your body and into your brain.  But a small amount of alcohol does go into the brain and when it gets there, the reason it makes us behave the way it does - and we all know what the effects are - at least in modest doses, is that alcohol increases the activity of one of the brain’s inhibitory nerve transmitter chemicals.  This is called GABA.  This damps down the activity of nerve cells.  So unlike certain drugs like ecstasy which can in fact make nerve cells more active and damage them, alcohol damps down the activity of nerve cells and therefore it makes them less vulnerable to damage.

Jennifer -   So they might live longer?

Chris -   Well, they may do.  The evidence is, small doses of alcohol probably don't harm neurons and the body’s pretty well set up to cope with it anyway.  If you look at people who have spent their whole life drinking modest amounts of alcohol, there’s evidence that actually their intellect may be preserved better than teetotalers.  That’s not saying, now, prescribe yourself daily alcohol intake to live a long time and have good brain function into old age.  That’s not what we’re saying.  But what we are saying is that epidemiologically, if you look at populations, the evidence is that it doesn’t do any harm.  There’s no evidence for significant harm in those people.  If you also look at people who are chronic alcoholics, unless they get a condition called Wernicke–Korsakoff's psychosis – which is where they run out of a vitamin called B1 (thiamine) which is very destructive to nerve cells – they don't actually have huge damage to the nervous system unless they are very, very, very heavy drinkers for a very long time.  So therefore, the evidence is that alcohol is probably okay in modest doses and most of the injuries and most of the damage to the brain happens when people get drunk and fall over and hit their head, or get into fights.  That’s actually the reason why head injuries happen with alcohol and why brain damage probably occurs.

Your hair is coloured because you have cells that pump pigment into the hair as it’s growing.  As you get older, these pigment cells basically get a bit knackered and they stop putting colour into your hair - which is why your hair goes grey.  It doesn’t actually go grey, in fact, it goes colourless.  It goes white, but against the background of darker hair, it may look gray.  This is because the pigment has stopped being pumped into the hair.

Also, pigment cells don't continually pump pigment into the hair.  They may take little breaks, going in a cyclical way, and so it’s perfectly possible for hairs to be different colours along their lengths.  It’s probably unusual that you’d have zebra print hair, but it is certainly possible that they might stop producing pigment for a bit and then start producing pigment again.

It’s obviously a very highly evolved behaviour because we are the only animals that do it.  Other animals, although this is possibly disputed by some scientists, don't appear to cry.  It’s thought that you cry in response to a stimulus, some scientists thought it might be to do with the build up of stress and hormones - a hormone called adrenocorticotropic hormone might actually be released through the tears.  So when you're in a stressful or unhappy situation, you actually release this hormone and get it out of your body through your tears.  There is evidence for certain hormones found in your tears, things like the hormone prolactin, other things like potassium and manganese.  And so, tears produced when you're crying for emotional reasons actually have more of these things in than tears that are just lubricating your eyelids.  So perhaps, you might be able to tell if someone is just faking it or just the got onions out by measuring these hormones in their tears. 

Interestingly, another thing about crying, women do cry more than men.  It’s thought to be to do with certain hormones that are only found in women.  As studies showed on average that men cry about once a month, women cry about five times a month on average.  (More around the time of the month ladies.)

The other interesting thing about crying is that it may well have evolved as a communication signal to say, “I'm really unhappy and I need a cuddle” or “I'm really upset.  I'm really angry.  I'm really stressed.”  Because obviously, people can see your tears and respond to them, so it may well be some kind of signal - showing that you're vulnerable, that you're unhappy - that other people can respond to.

If you look at skin and if you look closely, you’ll see that on the surface of the skin there are lots of little tiny pits or holes.  Those are pores.  These are tiny little glands, or the openings of little glands from glandular tissue which is deeper in the skin.  That glandular tissue produces various chemicals, mainly oil based ones including sebum which oozes out from the gland and nourishes the overlying skin and also controls the chemical environment of the overlying skin.  It controls, for instance, the growth and proliferation of various microorganisms.

The thing is, these glands are very sensitive to androgens, testosterone-like chemicals in the blood stream.  When a person goes into puberty, the time when the secondary sexual characteristics form, the levels of testosterone in both girls and boys increase enormously.  This makes the gland tissue in the skin dramatically increase its productivity of these oily chemicals and as a result, the skin becomes a lot greasier which can affect the proliferation of certain micro-organisms.  Certain microbes survive better under those conditions and it also means that it’s more likely that the little ducts that drain those glands can become obstructed, either by the oil itself or other things applied to the skin like creams, lotions or just dirt and grime.

If they become obstructed because they’re producing much more material, then bacteria, which can get into them, can overgrow within the blocked gland and the overgrowth of the bacteria can then trigger inflammation.  When you have inflammation, the immune system comes in and attacks the bacteria, and in the process it produces inflammatory chemicals that open up blood vessels, they wind up nerve cells and they also attract other components of the immune system which makes the area get red, hot, swollen and tender.

As the micro-organisms are attacked by the immune system, the white blood cells that come in to do that can also die in the process.  This is what produces pus, or the yellow stuff you get inside a spot. It’s a good idea not to squeeze a spot, because although sometimes the stuff can come out in the right way, what can happen is instead of splurging out the front, the pus-y inflammatory debris inside the spot can sometimes go sideways into the adjacent skin tissue.  This spreads the infection and also increases the degree of inflammation and this in turn can damage the underlying skin tissue which can produce more swelling and if it’s very bad you can get scarring.

Some people are more prone to spots than others.  Probably because some aspects of their genetic make up might mean that they have certain populatons of bacteria on their skin that are more likely to provoke spots.  It may be that they’re more sensitive to testosterone and androgens and this makes their glands produce more of this oily material in the first place.  Both of those in combination can conspire to make some people more prone to acne and spots and they way they react to those bacteria with inflammation for example.

So the long and the short of it is that unfortunately it’s a consequence of growing up.  As you get older, the amount of testosterone being produced in surges drops a bit and therefore the skin acclimatises and becomes less greasy.

But for people for whom it’s a big problem, you don’t have to suffer in silence because there are some good treatments.  In people who have chronic cases,  antibiotics are very effective.  Members of the tetracycline family of antibiotics are very good and taken for about 6 months, they can sometimes eliminate the bacteria that are causing the problem and prevent any more skin damage.  This means the skin then has a chance to recover.  If it does recur you can simply start the antibiotics again.

Obviously antibiotics are dramatic measure and so you should try and use simple measures first.  Soap and water to get rid of the excess oil and then things like benzoyl peroxide creams which can help to take off the excess skin and stop the ducts from getting blocked in the first place.  But it is a big problem, luckily it does tend to improve with age.