How Drugs Work: Anti-depressants

This post was requested by the very lovely Bex, who is some kind of crafting Goddess. This post isn’t actually anything to do with crafting though, which is lucky because when I craft I usually tie things in knots, and glue bits of myself to other bits of myself, and it’s all a bit messy and less than brilliant. But as I said, crafting isn’t the point of this post, Bex has asked me to explain how anti-depressants work, and this post is specifically about a class of anti-depressants called selective serotonin re-uptake inhibitors (SSRIs).

Before I go on, I want to make it very very clear right now that this isn’t intended to advise you as to whether antidepressants are something that you need or will help you. Depression is an incredibly difficult and challenging thing to understand, and not everyone experiences it in the same way. If you think you may be suffering from depression, I would encourage you to contact your GP, or someone professionally qualified to help you. This is going to be about HOW certain anti-depressants are likely to work, but it won’t tell you if they’re right for you, that’s a decision for you and your GP, or for you to discuss with a counsellor.

So. Your brain. Your brain is so complex, it’s actually quite breathtaking. Messages are zipping and zapping about all over the place. Nerve cells pass messages along their lengths in the form of negative charges called action potentials. These super little impulses shoot along nerve cells, like Road Runner on speed, until they reach the end of the line and come to a sudden halt. A huge canyon looms ahead of them, a synapse, with another nerve cell on the other side. The message has to get across the synaptic gap, to get to where it needs to go, but the action potential just can’t make the jump. It would be stuck, shouting into a void, were it not for the existence of some handy neurotransmitters.

Neurotransmitters can cross the canyon of the synapse. They have specially designed clever gear that allows them to be released, with a leap, from the surface of the pre-synaptic nerve cell, and fly across the chasm, where they are caught by receptors on the surface of the post-synaptic nerve cell. Neurotransmitters are terribly brave, casting themselves across the gap without caution, trusting that a receptor will be there to greet them, and take their message forward.

Once they’ve successfully traversed the gap, and passed the message to the receptor on the new cell, neurotransmitters have got to get back to their original nerve cell. Suddenly, they’re frightened. When there was an urgent message to share, they leapt bravely without thinking about it, but on the way back they suddenly realise how far they have to go, and panic. Instead of leaping back, they are released by the receptors, and collected by a kindly monoamine transporter, providing a shuttle service back to their original cell. This process is known as reuptake. If monoamine transporters didn’t come along to do this job, the neurotransmitters would hang around at the edge of the gap, clinging to the receptors, and yelling their message repeatedly.

Serotonin is one of the intrepid synapse-crossing neurotransmitters, and what SSRIs do is slow down the reuptake of serotonin into the original nerve cell, thus leaving it in the synaptic gap longer. This means that serotonin keeps on clinging to the receptors, and keeps shouting out its message to the receptor cell. SSRIs may also work in a similar way to strand dopamine and norepinephrine in the synpatic gap. The implication is, of course, that low levels of serotonin, dopamine and epinephrine are linked to depression.

So, that is the mechanism of action for SSRIs; however with depression nothing is simple. Not all depression is necessarily linked to or caused by low levels of serotonin, dopamine or norepinephrine, so often taking SSRI anti-depressants is a trial and error experience, it won’t automatically work for everyone.

On top of this, there is another level of confusion, as there so often is in biochemistry. There is another drug that can have anti-depressant effects, tianeptine, which is actually a selective serotonin reuptake enhancer. It acts in the complete opposite way to SSRIs. This clearly doesn’t make sense, unless the links between serotonin, dopamine, norepinephrine and mood are a lot more complicated than we thought. This means that although we know what SSRIs actually do from a molecular perspective, we’re still not entirely sure how that relates to depression.

Ultimately, there’s no way of knowing, at the moment, whether SSRIs are likely to work for you. And on top of all THAT, there can be adverse side effects to SSRIs, much like with any drug. Again, and I hate to repeat myself, but this is super important to me, this is a thing that you should discuss with your GP if you think you’re suffering from depression, and want to talk about getting help.  The conversation about risks and side effects and the decision to try SSRIs is something for you and your Doctor, not something that a nerdy science blogger can solve. A nerdy science blogger can just sit here and tell you that whether or not they work for everyone, the fact that we as human beings can actually design a drug that can work somewhere as complicated as your brain, on something as misunderstood, complex and awful as depression, is pretty damn amazing.

As part of this post I would also like to say that I wholeheartedly support the Time for Change campaign, which is working to destigmatise mental heath issues and end discrimination against people who suffer with them. 

Kitchen Science: Melting Cheese

I received a text from my sister a few weeks ago, asking me about cheese. I consider this a good thing, because I love cheese nearly as much as I love new science questions. I mean, who doesn’t love cheese? I’m pretty sure the answer is no-one. Anyway, the question Emma asked me was about melting cheese, which is possibly even better than just normal cheese, all gooey and melty and tasty and delicious…. Ahem. Sorry, lost myself there. What she wanted to know was what makes different cheeses melt differently, so for example why does melting camembert or brie produce a consistency that can be spread with ease, or dipped into, while mozzarella produces a stringier texture that streeeetches out? Why does cheddar melt into a consistency somewhere between the two, it can be spread on toast, but will stretch slightly when you bite it. What’s the crucial difference between these cheeses that affects the melt?

I wish I could say that in order to answer this question I needed to carry out extensive research by eating and analysing many cheese samples. Sadly, no such luck, the answer is already out there. That said, all this talk of melting cheese may result in me failing the ‘walk past the amazing-looking cheese shop on my way home from work’ willpower test…

When cheese melts, what’s actually happening is a two-stage process. First, the fat molecules melt from solid to liquid; this can happen at fairly low temperatures and sometimes results in visible beads of melted fat on the surface of the cheese. I think we’ve all accidentally left cheese on the kitchen side in the summer and seen THAT phenomenon. Unless the rest of you are efficient types who put cheese away when they’re done using it. I’m usually too busy eating what I made with the cheese to deal with the remaining cheese on the side. Anyway, that’s stage one; fat beading.

Stage two is when the casein proteins get involved, and things really start to heat up. What happens is that increasing the temperature causes the bonds holding the protein structure together to shake, and shimmy, and generally party so hard that they break free from their nice ordered position, wave their arms in the air and act like they just don’t care. Once the bonds begin to break, the structure of the cheese sort of… gives up. It collapses into a thick, gloopy, melted pile of deliciousness. It’s a party that ends with melted cheese everywhere, which is clearly the best kind of party.

It’s a cheese party!
Image credit.

So that’s how cheese melts, however, that still doesn’t explain why not all cheeses melt the same. For starters not all cheeses melt at the same temperature; softer cheeses melt faster and at lower temperatures than hard cheeses. What decides the melting point of a cheese is the water content; drippy wet soft cheeses, which contain lots of water, have proteins that are quite dilute, the volume of water means that the proteins cannot bind together so tightly, and it takes less heat to break their bonds and get them partying. On the other hand, a rock-hard tough cheese like Parmesan, the Terminator of cheeses, has dense proteins, tightly packed and holding on tightly. It takes a lot of heat to get the Terminator partying. And even when the protein molecules do break down and have a little boogie, they don’t really let it all out and sag like an uninhibited Brie, they still remain relatively sedate and confined.

Stringy cheese. Yum.
Image credit.

That’s why some cheeses melt to a dippy goo, but why do some other cheeses go stringy? The stringiness comes when the casein molecules are still mostly intact, they haven’t quite given way to urge to dance like no-one is watching. Instead, they are linked together by calcium molecules. In my mind, the calcium molecules help the casein to form a conga line, so that rather than dancing loosely and flowing freely, they stick together in long chains that stretch out and bump into one another on the dance floor. The level of conga formation depends on the conditions under which the cheese was made; for example a high level of acidity means that there is less calcium hanging around. Cheeses in this case are less stringy, and more gloopy.

So, there you go. Melted cheese is just one big dance party. And if any one of you doesn’t feel an overwhelming urge to eat cheese on toast right now… you’re stronger people than me.

Your Body: Thyroid Hormones

Happy Friday, science fans! Don’t forget, you can now ‘like’ The Molecular Circus on Facebook, and follow new posts and science chatter over there.

Today’s post was requested (quite a while ago) by both Siobhan and Matt, and it’s about how hypothyroidism works. Hypothyroidism is a condition that arises when the thyroid gland just cannot get motivated, and lies around all day consistently not producing enough thyroid hormones to do all those tricky jobs that thyroid hormones need to do. In order to understand how hypothyroidism works, it’s pretty key to find out what thyroid hormones do. And actually, understanding that also explains how hyperthyroidism works too.

The life cycle of a thyroid hormone

The thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are produced by follicular cells in the thyroid gland.  They only do this when under strict instructions from another hormone though, the boss of thyroid hormone production, thyroid-stimulating hormone (TSH).  TSH carefully regulates the amount of thyroid hormones that the body produces; when there’s a lot of T3 and T4 about, it instructs the thyroid to slow things down, and when there’s very little T3 and T4 to be seen, anywhere, it takes up a megaphone and startles the thyroid into rectifying that immediately. Unlike most hormones, T4 and T3 don’t peak at certain times; in fact the very raison d’etre of TSH is to keep the level of thyroid hormones as steady and constant as possible.

When TSH does need to produce hormones, it stimulates follicular cells, and they absorb a protein called thyroglobulin. This protein has been captured for use by an enzyme, thyroid peroxidase, which traps the protein with iodine. It then passes it to the follicular cells, who strip the protein for parts; taking the iodine-trapped residues of tyrosine amino acids from it, and using them to form T4 that can then be sent out into the big wide world, or the if wide human body, at least.

As hormones go, T4 has a lovely life, really. Once produced, it whizzes around the body via the circulatory system by hitching a ride with passing proteins. Usually, a protein called thyroxine-binding globulin (TBG) takes pity on it, idly hanging about by the roadside, or blood-vessel side, and picks it up. Once it’s piggy-backing on TBG, it is are inactive, so it can ride around the place for ages, just sight-seeing, not getting up to much. However, when necessary it can let go of TBG and exist in the bloodstream as free and active T4. This is when it is needed to make changes, be proactive and generally Get Important Things Done.

However, T3 is actually quite a lot more efficient than T4 at Getting Important Things Done. T4 is a bit of a hitch-hiking loafer, but T3 is highly motivated and ready for action; so when T4 reaches the place it needs to be, it is converted to the hyper-efficient T3 and that’s when the Important Things starts Getting Done.

Thyroid hormones bind to a thyroid receptor, and in doing so trigger a series of cellular signals that lead to changes. They are the hormones responsible for regulating metabolism and energy balance; amongst other things they increase the metabolism of carbohydrates in the body, increase heart rate and cardiac output, increase the body’s base metabolic rate, and increase the effect of catecholamines in the brain. They basically speed everything up a bit, and keep things running. The fact that they are so important is why it can be such a big issue to have not enough of them… or too much.


Hypothyroidism occurs when the body cannot produce enough T3 and T4, there are a variety of possible reasons for this, one of which is a lack of iodine. Considering how crucial iodine is to making thyroid hormones, you can imagine that a serious lack does inhibit production, with some seriously rubbish effects.

When the body cannot produce, for whatever reason, enough thyroid hormone, metabolism slows down. This typically results in weight gain, a feeling of tiredness, slow heart-rate and a real intolerance for cold temperatures. A lack of thyroid hormones being produced can also cause the thyroid gland to swell to form a lump or goitre, in an attempt to solve the problem; however if the problem is that there is simply no iodine to be found, no amount of thyroid growth will help.


By comparison, some thyroid glands are just too excited. Instead of not producing enough thyroid hormone, they produce far too much. The symptoms are very much the opposite as well, instead of slowing down, your body reacts as if someone had hit a fast-forward button; you may get heart palpitations, excessive sweating, weight loss, and muscle weakness. Your body is just trying too hard.

In both cases, the carefully regulated levels of hormones are all over the shop. This is the real wonder of hormones, the tiniest fluctuation matters; everything is balanced perfectly, on the edge of a knife. One wobble, and everything can go wrong.


How Drugs Work: Antihistamines

Hello, my molecular massive! You may have noticed a slight absence of posts last week; my exciting new job has been taking all my brain power, all that remembering new names and learning what to do, and loving it. Regular posting will resume as I settle into a rhythm of blogging in the evenings, in amongst training for the triathlon I rashly entered in July, and obviously habut in the meantime here’s one I wrote earlier. As the sun has finally made an appearance this year, this seems a timely subject….
If you’re anything like me then you might just love spring; love the colour, the flowers, the trees, and the lush effervescent greenery of it all. But if you’re even more like me, your enjoyment of this festival of life and growth may be occasionally curtailed by the inevitable contact with flecks of pollen spinning gaily through the breeze, transforming of your head into a leaky, red-eyed, sneezing ball of misery. Yes, I’m talking about hay fever. This weekend, for the first time this year, it really felt like spring. Almost like summer. It makes me want to go and lie in the grass in a summer dress, with a daisy chain in my hair. And I want to do so without puffy eyes and a streaming nose ruining my picturesquely romantic image. To do this, I’m going to need my faithful antihistamine.
A meadow of spring flowers just waiting to make me sneeze.

A meadow of spring flowers just waiting to make me sneeze.

Antihistamines have a fairly self-explanatory name; they alleviate the effects of histamine on the body. And anyone who’s ever experienced hay fever, or any other similar allergic reaction, will know the effects of histamine well. A runny nose and red puffy watery eyes. Perhaps some itching, some pain, some redness of the skin and some swelling. 
An allergic reaction is your body assuming that something harmless (pollen, for example, or cat hair) is a dangerous invader. And once it senses the invader, it sets into action an inflammatory response. The job of sensing invaders is down to antibodies, and the antibody that senses and binds to allergens is immunoglobulin E (IgE). IgE antibodies live on the surface of cells that are specifically designed to be involved in the inflammatory response, mast cells and basophils. Once the IgE has bound to an allergen, it sets off a series of events within the cells that lead to degranulation, the process of releasing molecules that mediate the immune response. Amongst these molecules is histamine.
Histamine, once released, causes effects on the body by binding to histamine receptors. There are four types of histamine receptors, H1–H4, but the key receptor involved in hay fever and allergic reactions is the H1 receptor. Histamine binding to the H1 receptor has a number of effects. First, histamine causes an increase in vascular permeability; this means that the walls of blood vessels are altered to allow more water and small molecules to pass through them. Water leaving the bloodstream can pass into the surrounding areas, often causing swelling, for example in response to an insect bite. This may also be responsible for watery eyes. 
Second, histamine causes increased mucus production, leading to a runny nose and, after a few hours of exposure, congested nasal passages. Histamine also causes an itching sensation in the immediate area of its release, in hay fever this tends to be in the back of the throat, the nasal passages and the eyes. The eyes also water in an attempt to remove the cause of irritation, and may become red and swollen. Finally, histamine can cause smooth muscles to contract, particularly the muscles in the airways, causing shortness of breath and an asthmatic-type wheeze. 
Taking an antihistamine then, prevents these effects. The drug competes with histamine to bind the H1 receptor, and wherever the drug wins and binds the receptor, histamine cannot, and therefore it also can’t cause any of the irritating effects above. Since they bind competitively, antihistamines are more effective if you take them before you come into contact with your allergen so they have the best possible chance of out-competing the allergen for the receptor. It’s like getting a good head-start in a molecular gladiator battle. 
Side effects: staying awake at the wheel
Antihistamines are relatively free of side-effects, but the most well-known is drowsiness. Drowsiness is caused by the drug crossing the blood–brain barrier (BBB), which is the barrier that exists between the circulatory system and the nervous system to stop just any old molecule getting into the brain and causing untold havoc. The first generation of antihistamine drugs, which include diphenhydramine, tended to cross the BBB relatively easily, and once there were able to act to cause sedation and drowsiness. Second-generation antihistamines, however, have been modified to prevent them crossing the BBB so much. Most common over-the-counter antihistamines (including cetirizine and loratadine) belong to the second generation and therefore are much less likely to cause drowsiness. However, some drug may still be able to cross the BBB and for that reason, some people (including myself!) may still find drowsiness a side effect of the drugs. If this is the case for you, you know the rules…. don’t operate heavy machinery. 
So, that’s how histamine causes the effects of hay fever, and how antihistamines stop them. Now, if you’ll excuse me, I have a date with an antihistamine tablet, a patch of grass and a daisy chain. But no heavy machinery.

The Friday Question: Why Do We Hiccup?

This week’s Friday question was asked by the very lovely Zan, and it was about the science of hiccups. Why do we get them? What are they for? And how can you make them stop?

The science of hiccups is a funny thing, we know what a hiccup is, and we know some of the things that cause them, but we don’t really know what good they do. I should note that this post is about common hiccups, which most people get and which pass within an hour. There are also more serious, and longer lasting, types of hiccups that can be caused by nerve damage, drugs or illness.

A hiccup is a sudden short intake of breath; normally when you breathe air goes into your mouth or nose, and heads to your lungs via a scenic tour of your trachea. On its way to the lungs air passes through the pharynx, the space behind your mouth and nose, and heads past the epiglottis, which is the crucial little bit of you responsible for keeping your airways and your oesophagus separate, and protecting your vocal cords. Below the epiglottis is the larynx, home of the vocal cords. Air whizzes through here and heads on down the trachea to the lungs. It’s all very leisurely and straightforward, a pleasant walk in the park.

A hiccup is a disturbance in this lovely easy breathing pattern. Your diaphragm, which lives underneath the lungs, like a troll under a bridge, usually helps the process of breathing by lifting up when we breathe out and moving down when we breathe in. The diaphragm is a weightlifting troll, although to be fair it is only lifting air, which isn’t that impressive. I can totally lift air. Anyway, the movement of the diaphragm is controlled by the phrenic nerves. If anything irritates these nerves, they send a message to the diaphragm that causes it to spasm, snapping suddenly downwards and leading to a short sharp intake of breath. In response to this unexpected sudden breath, the epiglottis speedily shuts; this is the ‘hic’ sound we all know and love.

This is all very well: hiccups are caused by our phrenic nerves getting irritated and forcing the diaphragm troll under our lungs to suddenly squat down low, but what exactly is irritating our phrenic nerve in the first place? Actually, our phrenic nerves are clearly very moody, irritable little things, because quite a lot of things can annoy them into causing hiccups. One of the most common is eating too much, or swallowing too much air; when your stomach is very full, all stretched out and rounded, it can push up against the phrenic nerve, which irritates it. Other things that irritate the phrenic nerve include very spicy food, drinking alcohol, drinking something very cold or very hot, and sometimes emotions like stress or shock. Basically, the phrenic nerve is the Grumpy Old Woman of the nervous system.

These are some reasons that we get hiccups, but none of them makes sense as the actual purpose of hiccups in general. In fact, nobody really understands the purpose of hiccups. There are some theories; one is that they’re an evolutionary hangover from a time when we had gills. Creatures with gills need to close their epiglottis to stop water going into their stomach while they force it across their gills, and the process involved in this is similar to the process of a hiccup. This theory also suggests a reason that hiccups have hung around this long; it might be a mechanism to help young mammals learn to suckle, without accidentally inhaling milk into their lungs. Another theory, on the other hand, suggests that a hiccup is a complex process developed to remove air from the stomachs of young mammals.

Neither of these theories is necessarily correct, and there are other theories out there too, I just found those two particularly interesting!

Regardless of why we hiccup, hiccupping can be annoying, so despite the fact that they will usually pass of their own accord fairly quickly, we always try to stop them. I think everyone was told a different way to stop hiccupping while they were growing up, from eating a spoonful of sugar, to holding their nose, to making someone jump, or drinking water upside down. Zan told me she has to drink water WHILE holding her nose.  I always take a huge deep breath, a mouthful of water and swallow in 12 tiny sips. The actual key to controlling, and hopefully stopping hiccups, is really to control your breathing and your diaphragm. Most hiccup home remedies that actually work will involve some way of regaining control of your breathing muscles; for example both mine and Zan’s methods involve holding our breath, which squashes the diaphragm flat and hold it there, so that it can’t spasm.  Whatever your method, if it works for you, then go with it, there’s no scientifically proven single cure for hiccups anyway. Although it is a nice excuse for a spoonful of sugar.

Entropy Kitchen: Chocolate Chip Cherry Cheesecake

I thought hard about which recipe to include to go with Monday’s whipped cream Kitchen Science post. In the end, I settled on this recipe, which I found on Pinterest and recently made for my family. It was very tasty, summery and involved me over-whipping cream, because I hadn’t yet written the post about why you shouldn’t do that. Nonetheless, it was still good, and to testify to this I have absolutely no photos of the cheesecake that I made, because once I had served it, it didn’t last very long.

Chocolate chip cherry cheesecake

Rather than typing out the recipe here, I shall refer you to the original post. I followed Steph’s suggestion and didn’t make the ganache for the top, and it was still absolutely yummy. Light and creamy and delicious. I also had to use tinned cherries, because fresh cherries are out of season at the moment, and I couldn’t get hold of any.  I’d like to try again with fresh cherries though. I also used larger chunks of chocolate than the recipe advised, mainly because I had bought chocolate chunks from Waitrose, and I was in a hurry to make some scones after the cheesecake so I just chucked them in! I quite liked the bigger chunks though, because I’m a chocolate fiend.

Finally, I am including below my standard non-bake cheesecake base recipe. I found  the base of this cheesecake to be a bit crumbly and dry for my personal taste (I like BUTTER, darn it), so if I make it in future I’m going to make the base my way. If you prefer a less buttery base though, I would use the original recipe, here.

Overall, this was SUCH a yummy dessert, I definitely want to try it again. I’m also interested in trying it with raspberry and white chocolate, or blueberry and milk chocolate. The cheesecake possibilities are endless, and luckily now I know why I should stop whipping the cream when it looks finished!

Basic cheesecake biscuit base

12 digestive biscuit
85g butter
1 tbsp golden syrup

This is a very straightforward recipe. Melt the butter and syrup together. Crush the biscuits into crumbs. Mix the butter and syrup into the biscuits, then press into the base of your cheesecake tin. Pop in the fridge until your topping is ready. YUM.

Kitchen Science: Whipped Cream

Well. That was an unexpectedly drawn-out blog holiday, was it not? Lovely science fans, I am so sorry the delay… it all started with a week in Cornwall. Unfortunately for my holiday, but fortunately for my career, I had to cut short my Cornish idyll to rush home for some job interviews, which I then got offered. I have spent the past fortnight finishing up freelance work, equipping myself to do a job where I don’t work in my pyjamas in my spare room, and generally giving myself a bit of a break to celebrate the end of months of rubbish job hunting. By the time you read this, it will be my first day in my new job, which is exciting. So, I apologise for the extended blog break, sometimes a girl just needs a holiday. And a new job.

Anyway, before I went away, Kat sent me a kitchen science question. She asked me “why does whipping cream make it go stiff? And does temperature have an effect on the time it takes to whip?”

I actually love this question. I love when people ask me questions for the blog anyway, and I particularly love when they ask me things I had never thought to wonder about but immediately NEED to know as soon as I get asked. In fact I read this question in the supermarket, and forced my husband to come and spend 5 minutes with me reading the labels on the various pots of cream trying to figure out the answer myself.

I figured that there must be a clue to the answer in looking at the difference types of cream, because single cream is difficult to whip into a stiff foamy solid, whereas whipping cream or double cream is considerably easier. The most obvious difference between a pot of single cream and a pot of whipping cream, apart from the different coloured packaging, obviously, is the fat content. Single cream has around 30% fat, whereas whipping cream has 36-40% fat. Double cream has 45%+ fat content. It was fairly easy to assume that this is the crucial difference that allows the change in consistency. And indeed, it is, but what’s more interesting is how it works…

Cream is basically fat-full, low-protein milk; if you leave fresh milk alone to stand then globules of fat naturally float up to the surface and bob around, creating a fatty creamy layer of deliciousness that can be skimmed off the top, leaving the majority of the protein behind. This cream, with its high fat content, can be whipped.

Whipping creates air bubbles. This is actually true in any liquid, if you whisk water it becomes bubbly, however the bubbles have no strength and are liable to pop at any moment. If you are going to create a solid mass of trapped air bubbles, you need something to keep them in place. This is where fat comes in. Fat hates water; it cannot stand to be around it. This is why fat tends to form globules in water, it arranges itself so that only a small outer region that doesn’t mind the water faces outwards, leaving the rest of the cowardly molecules to hide themselves away from the big scary water. Whipping, however, disturbs the fat. The globules are forced to whizz around the place and bash into one another. The protective membrane that shields the globules from the scary water is ripped away by all the whizzing and bashing. Fat is suddenly naked in the face of the water.

This is not something that fat molecules can cope with; once they have been forced out of their globules they will choose to arrange themselves in one of two ways. Either they will face air, or they will face each other. Arranging themselves like this forces them to form a network of fat surrounding air bubbles, trapping them in place. And there you have it, stiff fluffy whipped cream.

Perfect fluffy whipped cream. Who would have thought frightened fat and trapped air could be so delicious?!
Image credit.

However, it is possible to over-whip cream, as I know only too well, because I have a tendency to assume that more force = better in the kitchen. Now that I understand the science behind why this is not at all true, perhaps I will learn, because continuing to beat the cream after the fat network has trapped the bubbles actually destabilises the network, the fat begins to be able to reform globules of pure fat, making the mixture greasier, and liable to weep. Poor sad over-beaten cream.

Finally, Kat also asked me whether temperature makes a difference on how long cream takes to whip. The short answer is… yes. Colder cream whips faster. Warmth softens the fat, weakening the framework that traps air bubbles. So if you want perfect fluffy whipped cream you need it to be cold, with a high fat content, and to know when to stop. Otherwise you’ll make your cream cry.

How Drugs Work: Aspirin

Aspirin has a reputation as something of a wonder drug. It was originally developed as a painkiller, but in the past decade it emerged that it can help to prevent heart attacks and strokes in patients diagnosed with coronary heart disease. It has been suggested that taking it can reduce the recurrence of deep vein thrombosis. It has been shown to reduce fever. And, on top of this, trials suggest that it might help to prevent colorectal cancer. Yep, that’s right, if aspirin wore pants, it truly would wear them over the top of its leggings, like an all-singing, all-dancing molecular superhero. But honestly, how can one drug do all this? How does it do any of it? I’m tired just thinking about trying to do that much in one day, as I sit here typing in my pyjamas. Aspirin is capable of so much, because it has a truly amazing nemesis…

Aspirin: here to save the day!

Aspirin: here to save the day!
Image credit.

Aspirin as a painkiller

Aspirin is classed as a non-steroidal anti-inflammatory drug (NSAID), it reduces pain by reducing inflammation. Inflammation is a process your body uses to heal wounds, patch up problems, repair damage and fight infection. Amongst other things, inflammation causes pain. This seems a bit counter-productive, why should it hurt to heal yourself? The pain is there to make sure that you’re aware that something is wrong; it’s an alarm system, a siren flashing CODE RED to your brain to make sure you’re aware of the damage, and the need to protect the painful area while it heals. Basically the pain is there to make sure you don’t ram your injured body part into a wall, or anything daft like that.

In order to react to damage, your cells have an inflammatory response team, who come complete with excellent theme music, like the A team. This inflammatory team includes an enzyme called cyclo-oxygenase-2 (COX-2). COX-2 has a job; its job is to convert arachidonic acid into prostaglandin H2. This may not sound like a dream job to you, but it’s an important role, and COX-2 sees it as something of a calling. Once COX-2 has converted arachidonic acid into prostaglandin H2, the prostaglandin then goes on to be changed into prostanoids, which are key players in mediating the inflammatory response: once the prostanoids are on the job, inflammation is happening.

Unless, that is, aspirin is hanging around. Aspirin targets the COX-2 enzyme, and whenever it finds COX-2 it attaches a chemical COCH3 group to it. With the chemical group blocking it, COX-2 is unable to fulfil its calling, and arachidonic acid remains unchanged, reducing the number of prostanoids and thus reducing the inflammatory response. Aspirin is such a bad-ass NSAID that even once it has left the area, presumably to save a child from a burning building or something equally molecular superhero-like, the COX-2 enzyme that has been blocked cannot function. Your body is required to make new COX-2 enzymes from scratch before it can start producing prostanoids to get on with the inflaming again. While the majority of COX-2 enzymes in the area are blocked, therefore, the inflammation and pain in the area is decreased.

Aspirin in coronary heart disease

Prostaglandins are not involved in inflammation alone. One particular prostaglandin, thromboxane A2, plays an important role in the aggregation of platelets in the blood. Sometimes, this is a really handy thing, if your platelets didn’t aggregate in certain circumstances then you’d never stop bleeding once you cut yourself, and it’s pretty evident that that would suck. However, if you suffer from coronary heart disease, then platelet aggregation can lead to blockages in your arteries, and these blockages can lead to heart attacks or strokes. If aspirin blocks COX-2 in this situation, less thromboxane A2 is produced, and the blockages may be reduced.

Aspirin in bowel cancer

So what of the claims that aspirin can help to prevent bowel cancer in high-risk patients? How does it do THAT? Freeze ray? Sadly not, cool as that would be. There are several theories on this, but one of them suggests that it all comes down to COX-2 again. COX-2 is suggested to be over-produced in adenomas, which are usually the starting point for the development of tumours in bowel cancer. Unfortunately, the role of COX-2 in adenomas hasn’t been fully established but it does seem that it has a role in increasing their growth, which is one of the key things that you want adenomas NOT to do, really, because that’s when they start to turn cancerous. In this situation, aspirin once again blocks the action of COX-2, and in theory prevents the growth of adenomas.

So that’s it; the basics of how aspirin became a molecular superhero. Most theories suggest it relies on the brilliance of COX-2 (although this post is by no means exhaustive, and there are other theories, there are pages and pages and pages of studies on aspirin out there, some of which have been linked to in the comments below). COX-2 is the true star of the show, it has such a wide range of roles within the body, and these varying roles allow aspirin to work in a range of different ways. Aspirin is so impressive because it targets such an impressive enzyme. If COX-2 is the evil nemesis to aspirin’s superhero, then like so many evil villains, it is actually a misunderstood hero.

*Please note, guys, I am not a doctor, I’m just a really nerdy pharmacology enthusiast who likes to know how things work, please don’t start taking aspirin like superhero smarties unless you’ve spoken to your actual doctor. Do feel free to eat actual smarties though.*

The Friday Question: Why Do We Yawn?

Over the past few weeks, I’ve received LOADS of really interesting questions to address in this Friday Question slot, many of which I had never wondered about, which is really cool! So, if you asked me something, keep your eyes open, over the next weeks and months I’ll be doing my best to find answers to all your questions. And if you think of a question, do email me at, others can attest that I am always very excited to receive mail, especially mail with questions. Today’s question was posed by the excellent Lara, whose blog posts always makes me feel like I want to be her friend, and also like I need to go take several million creative writing classes, so perfect is her way with words. Sorry this post was a long time coming, Lara…

I love questions with a simple answer I can easily understand, I love it when the world makes perfect sense. At the same time, there’s something about a question with no easy answer, something about the mystery of it, the sense that there is more out there to be discovered and understood. That is the joy of science, after all, both the wonder of knowledge and the knowledge that there is always more to learn. Why do we yawn is one of those questions without a single proper answer, instead we have a collection of possible theories that might explain what’s going on, or indeed that might not.

Wake me up, before you go

One of the major yawning theories, and the one that I have mostly been told in the past, is that yawning wakes your brain up. The theory goes that a big yawn increases blood flow to the brain, particularly to the area associated with co-ordinating movement, consciousness and memory. This helps the brain prepare for action, should action be necessary. From an evolutionary point of view, this would explain why we often yawn when we’re tired, or when we first wake up. These sleepy times moments are lovely when you’re snuggled up in bed, but if something big and bad was about to eat you, being sleepy and drowsy wouldn’t be the best way to survive. This theory suggests that yawning is like a warm-up drill for your brain, and it’s backed up by studies that show people often yawn before events that require them to be alert, like exams, or heading on stage. These studies aren’t conclusive, though, it’s impossible to assume that just because these people are about to do nerve-wracking stuff, it’s the nerve-wracking stuff that is making them yawn.

It’s getting hot in here

Another commonly heard theory, and this is another one that I’ve been told in the past, is that yawning cools your brain down.  You do a lot of thinking, day-to-day. Even when you’re not really thinking about anything very much at all, when you’re watching rubbish on TV and your brain is idly pondering whether you can be bothered to go make a cup of tea, your brain is still busy and complex and active. And, like any busy and complex and active machine, this might lead to some overheating. Of course, air doesn’t rush to your brain when you yawn, but the rush of cool air into your head may cool down the surrounding equipment. I actually quite like this theory, because it means every time I yawn I’m justified in believing that it’s because my brain has been working really hard at thinking, and needs a rest. This theory is supported by studies that show people yawn more commonly in winter months, which is presumably because the air is colder and will cool down the brain more effectively. Again, though, this is unlikely to be the whole story.

Get on up, when you’re down

Another theory thinks that yawning is linked to brain chemicals, and that the levels of chemicals hanging around have an effect on whether or not we yawn. For example, high levels of serotonin and dopamine seem to increase yawning. Unfortunately, no-one has any idea why this might be, unless it’s just that serotonin and dopamine get bored, and make you yawn for the fun of it. But that’s probably not it.

I feel your pain, man

The final yawning theory is linked to the fact that yawning is so contagious. For example, pretty sure that reading this article will have made most of you yawn, and quite possible everyone around you is now yawning. I’ve basically started a Friday yawning epidemic. The empathy theory of yawning is based on the fact that you’re more likely to yawn if someone you empathise with yawns, like a family member or close friend, or even just someone your own age or gender.   The idea is that yawning is based on your ability to share the feelings of another member of your group, something which also might have a distinct evolutionary advantage.

And, there you have it, no one conclusive answer to the question, I’m afraid, but lots of intriguing theories as to why we might yawn. The best part of it is that they’re probably all right, to a certain extent; yawning might be caused by different things at different times under different circumstances. This probably won’t stop me using the “my brain has overheated, look..” *yawn* excuse, though.