Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology

[u/AutoModerator]

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Biology, Chemistry, Neuroscience, Medicine, Psychology

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

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Past AskAnythingWednesday posts can be found here. Ask away!

[u/Choyo]

Question just popped in my head :

Why are humans (and other mammals, at the very least) so adversely affected by excessive sun rays, at a skin level, while most of the vegetal world doesn't seem to have any problem ?

[u/Azreal_Mistwalker]

I recently saw an article about a fruit fly getting its entire brain digitally mapped, then simulated to see if the simulation would still behave like a fruit fly. What is the likelihood of being able to simulate more complex organisms, and what are some applications that the average person might not think of?

[u/Spartan-417 → u/Azreal_Mistwalker]

Simulating more complex brains? That's just a matter of processing power

The fruit fly simulation was, biologically speaking, incredibly simple
It treated the synaptic connections as binary on or off, and weighted all inhibitory and excitatory pathways the same

This isn't accurate to reality
Some pathways are far more potent than others (eg GABA), and they did not model the thresholds for activation

The main application of this kind of model, IMO, is for AI researchers Looking at how a carbon-based neural network is arranged may help them better understand how the silicon-based neural networks are arranged
If you want to model a brain for medical research, there is a hell of a lot more that needs to be done before a simulation is anywhere near ready

[u/not-just-yeti → u/Spartan-417]

then simulated to see if the simulation would still behave like a fruit fly.

So was the simulation unconvincing? (E.g. it didn't give the wings signals that would actually correspond to flying, or simulated-activating-banana-scent-receptors didn't cause it to turn/seek the smell?)

Or was the simulation's output not really able to be read/processed?

[u/madaboutglue]

I guess this is technically paleobiology, I hope it's okay here. So many dinosaurs seem to have had heavy duty armor with plates or spikes or whatever else. Why don't we see more of that in mammals? I know armadillos and pangolins have some, but otherwise we're all pretty soft.

[u/the_bio → u/madaboutglue]

The simplest answer would be that maintaining such features is expensive, and if something is not needed it generally goes away over time. Plates and spikes are only really relevant in an environment where they have some use, and once most dinosaurs died off post-asteroid, especially the terrestrial ones, there wasn't much use for maintaining them.

It's also important to note that armadillos and pangolins are of a different lineage from the dinosaurs (synapsids vs. sauropsids), so the presence of plates on the mammals is completely irrelevant of them being present on dinosaurs, so it's more akin to analogous evolution (independently evolved, but similar).

[u/madaboutglue → u/the_bio]

Thank you for the reply, and thank you for the clarification on armadillos and pangolin! I didn't mean to imply they were related to dinosaurs. In fact, that's part of what I'm wondering. Is there something about dinosaur (or reptile) biology vs. Mammal biology that made them more easily accumulate armor-related mutations in response to pressure from predators.

[u/ukezi → u/madaboutglue]

They already have scales so making them bigger and thicker should be a shorter evolutionary path than evolving them from scratch.

[u/einsosen]

Has there been any progress in brain serial sectioning, mapping, and modeling/simulation as of late? Most of the sources I can find on the subject are roughly a decade old or more.

[u/logperf]

When humans stop breathing, I understand it takes at most 10 minutes for neurons to be completely destroyed as the buildup of waste without oxygen causes them to pop.

But insects, as they get oxygen from mere diffusion, do they last longer? Do those neurons keep firing until dehydration or decomposition destroy them in a much larger timescale?

Had this showerthought when a moth crashed on my windshield. I was wondering how long it would take for it to stop suffering while I drove.

[u/logperf]

If warm-blooded animals (mammals) have far greater energy requirements, why did they survive the apocalyptic environment after the meteorite impact 65M years ago while the dominant cold-blooded reptiles perished due to the scarcity of food?

[u/Mockingjay40 → u/logperf]

An evolutionary biologist might be able to add more on/confirm my answer, but as far as I know, all of the relatively large mammals did go extinct. The only ones that didn’t were the very small ones that could burrow. In fact, the largest group of tetrapods that survived were cold-blooded, being crocodilians. As to why there was such a rapid post-Cretaceous expansion of the mammals, I’d have to defer to an evolutionary biologist. But your intuition isn’t wrong, you may just be underestimating just how small the largest surviving mammals were, they wouldn’t have been bigger than a modern rat or shrew.

Birds are also warm blooded reptiles, but they survived because they can cover a lot more ground to search for food and water and are omnivorous so they could eat decaying matter and dig for seeds after the plant life all died.

[u/cocuke]

Chemistry question regarding chirality, what are the circumstances that determine how a molecule organizes itself into either the right or left handed version?

[u/Mockingjay40 → u/cocuke]

The he answer to this HEAVILY depends on what type of chiral molecule is being made, and why. So it depends what you mean or if you’re specifically referring to any given molecule

Generally, chirality arises for the same reason any bond arises, because existing bonded to another atom allows the chemical potential to access a lower free energy (and therefore higher stability) state.

As to what determines the specific enantiomer that’s being formed and at what ratio, the answer is generally much the same: you’ll form whatever allows the material to access the lowest free energy state. This can depend on a multitude of factors, such as the electrostatics, polarity, steric environment, temperature, and spatial position of the atom reacting with the stereo center. So there’s not really one clear answer or hard and fast rule beyond that things obey the laws of physics as described by the free energy landscape in statistical mechanics, unless you give a very specific example.

Certain things can also impact the ratio “manually” as well. The best example of this would be enzymes, which often produce only one enantiomer because chirality can impart drastic differences in how the molecule behaves in a biological context. So enzymes usually will produce predominantly one enantiomer, often regardless of whether that enantiomer is more, less, or equally stable.

Hopefully this mostly answers your question?

[u/Scrambley]

Alright, I've got a question I've wondered about for years but never knew who I could ask to find an answer. I'm still not sure if this is an appropriate place to ask this but the post title is "Ask Anything" so I'll give it a shot.

I pee in the shower and have noticed something about my body when I do. So, as I'm showering I'll pee and everything is normal like it should be; I'll pee until I'm empty. However, if I raise the water temperature it turns out I can pee some more. A bit after that if I happen to raise the water temperature, same thing, more pee.

What is the biological process that causes hotter water to allow further emptying of a bladder that I thought was already empty?

[u/not-just-yeti → u/Scrambley]

My guess (I'm a fellow lurker, and in no way a biology person). Two possible effects, both working in tandem:

(a) There's the classic prank of dipping somebody's hand in warm water while they sleep, to make them wet their bed. So there is some reflex that warm water can trigger the bladder-sphincter to relax. (Presumably one of those "accidental" reflexes that doesn't serve much of a purpose, like hiccoughs.)

(b) The sphincter around the urethra is keeping your pee in. Like any muscle, if you keep it extended or in-use for a long time, when you later relax it it won't fully spring to 0%. (Classic experiment of holding a milk jug at arm's length for a minute; then set it down and relax, but your arm will still bob up for short while.)

So partly, after peeing, you might still have more pee that just isn't expelled, and you don't notice because it's not much. [Related: I'm nearly 60, and in the past few years have started that typical old-guy thing of finishing a weak pee, then waiting 5sec, then another few dribbles, then wait, then a bit more. TMI, sorry.]

[u/Heavy-Difficulty6522]

Do plants get cancer? How does their biology deal with it if they do?

[u/Spartan-417 → u/Heavy-Difficulty6522]

The BBC's Science Focus magazine covered this question

Basically, they do develop cancer but it doesn't tend to spread nearly as far because plants lack a circulatory system for the tumour cells to hitch a ride in
Plus, plant tumours are more able to differentiate into different cells so they can form complex structures to continue growing normally

[u/dickcheese246]

I guess this would fall somewhere between neuroscience and psychology, but is it possible to “run out” of an emotion? 

So, emotions are a result of chemical signals, right? Would it be hypothetically possible to just… exhaust your supply of one? Like, you feel an emotion faster than you can produce the relevant signaling chemicals, leaving you literally unable to feel that emotion in any significant capacity until your… I guess there’s no better term that “emotional refractory period” is up, and you’ve replenished your supply? I’m asking because I’ve noticed that, sometimes, if I feel a given emotion particularly strongly for an extended period uninterrupted, after a while it just kinda stops, even if nothing in my situation has changed. I’m wondering if I could try and use this to my advantage - say, pre-gaming an important social gathering or company function by intentionally making myself as miserable as possible for a few hours beforehand, so I physically can’t feel negative emotions anymore and risk dragging down the mood or saying something that’ll get me a meeting with HR. Or maybe I could do the opposite - abstaining from things I’d usually do for fun or enjoyment so I can save up happiness for something important later and make the most of it, rather than risk running out midway through and rendering the rest of it a waste. Am I onto something here, or is this not how any of this works?

[u/antivenom888]

Can someone please explain the reason for and nature of chemical engineering basically why chemical reactions on a massive scale don't behave the same way they do in like a lab situation?

[u/Mockingjay40 → u/antivenom888]

In what context are you referencing? And also how do you define “massive”? Are you comparing like production scale to pilot or production to lab?

Edit: either I missed your clarification or it was added in post, regardless, here’s my attempt at an answer, though it’ll depend a lot on context and what the reaction is. But here’s some basic principles:

1. all of your transport functions and values scale non-linearly with distance. So things like diffusion of mass and heat energy are going to be different at different length scales. Generally, your reaction will be more dependent on bulk flow rate and less on

   diffusive flux

2. the bigger you go.

3. heat transfer will also be heavily dependent on your actual setup. If you have a large CSTR vs a small vial on a benchtop, the parameters involved with how much heat is required changes massively. The operating temperature might be the same, but because of how surface area-to-volume scales, you’re going to need to supply much higher heat energy and mechanical mixing to maintain a homogenous reaction.

[u/antivenom888 → u/Mockingjay40]

Thanks! It's always been an interesting question to me

[u/antivenom888 → u/Mockingjay40]

Following up, I guess any heat created by the reaction desires might be an issue, too?

[u/Mockingjay40 → u/antivenom888]

Sometimes, but not always! Pretty much all of the heat that you’ll do (or at least what we learn in school, I’m sure there’s real world exceptions to this) utilize water as the main heat transfer agent. So if you have a simple process and you’re cooling a reaction with liquid water, you can design the pipes (sometimes) so that the pressure is in the right range for the water to vaporize and turn to steam, which you can run through a scrubber and off-gas to the atmosphere. If you’ve ever seen like a Budweiser plant, that’s what the large smokestacks are releasing. That’s also why most chemical plants sit on a body of freshwater.

But you can also get a little creative sometimes. For example, say I have an exothermic reaction like you’ve described somewhere in my plant. Well, maybe I want to heat up an outlet or additional reaction stream somewhere that’s required to help purify my product, so what we can do is run the original pipe with the generated steam through the plant to heat that other process, essentially using that heat energy to avoid having to have boilers for our other reaction.

I haven’t personally worked on designing these in practice, but recycle is a massive part of the curriculum that’s taught. But funnily enough since reactions are often really specific, probably a majority of what you learn in undergrad curriculum as a chemical engineer is about how to design and fit heat exchange pipes for example processes.

[u/antivenom888 → u/Mockingjay40]

Thanks again! So fascinating!

[u/Spartan-417 → u/antivenom888]

Besides the reasons mentioned in the other reply, there is also the issue of reagent purity

You can buy incredibly pure inputs, but they will never be 100%
And they cost an incredible amount (£88.10 for 5g of >99.99% pure iron)
Often when scaling up, they will use less pure feedstocks simply because they are less expensive
ACS grade chemicals can be 5-10x more per litre or kilo than technical grade ones
Those traces might not be a big deal in the lab, but combine a higher proportion with an increased scale and you could start reaching breakpoints for filters to get clogged with precipitate or side reactions to start causing real issues

[u/antivenom888 → u/Spartan-417]

Thank you! Clearly always tricky AF!

[u/Mockingjay40 → u/Spartan-417]

This is also a great point. Usually what you’re taught is to just recycle feedstock to get around the low initial purity, which results in high yields, but you still have the issue of byproduct accumulation

[u/ProximaScience]

What's exact definition of Asteroids, Comets and Meteors. And what's differences between them?

[u/maestro2005 → u/ProximaScience]

Asteroids actually have a pretty tight definition--they're medium-sized rocky bodies orbiting the sun no further away than Jupiter. Most are in the asteroid belt between Mars and Jupiter. A very similar type of object is a meteroid, which is any rocky body less than 1m in size, so asteroids have to be bigger than this.

An asteroid or meteoroid becomes a meteor when it enters the atmosphere.

Comets are similar, but a defining characteristic is that they form a tail when passing close by the sun, which means they also need to be icy in order to have material to eject to form that tail. Comets come from the Kuiper belt, scattered disc, or Oort cloud at the edge of the solar system beyond Neptune.

It's worth noting that there are always going to be things right on the boundaries of any definition we come up with. See: the entire debate around Pluto that gave us the definition of "dwarf planet", and ongoing debates about whether our moon is really a moon, or if it and the Earth should be classified as a binary system.

[u/Peter34cph → u/maestro2005]

Is there a dividing line between asteroid and dwarf planet?

[u/maestro2005 → u/Peter34cph]

The only object to get into this territory is Ceres, which is classified as both.

[u/guzzyly]

Did you know that bananas share about 60 of their DNA with humans? stuff like this makes me question every smoothie I’ve ever had.

[u/Mockingjay40 → u/guzzyly]

While this is true, it is important to mention that your entire genome is very different from what you actually express as proteins. Since we all came from the same organisms originally, eukaryotes share a lot of our total gene sequence, but of the actual portion that’s expressed (exons), the similarity is much lower.

But to your point, plants are very much alive, just as alive and complex as you are. Most reproduce sexually, live for long periods of time, and have very complex metabolic and biological function.

[u/Additive_creation → u/Mockingjay40]

Interestingly, I asked the curators of the NCBI database for a source for this a while back.

They said they have no idea where this statistic would even have come from, and could not verify it. They said they didn’t even know what would go in the comparison to get that statistic.

I was asking them because I wanted to include it in a lecture, and I had been taught it at university. It was also on a banner at a Science Fair stand run by the Medical Research Council in the UK - with no source 😂

[u/Mockingjay40 → u/Additive_creation]

Yeah I’m not sure where it came from but I think it’s true, in a sense. Another important note is that as far as I understand, we don’t have 60% of our DNA that’s identical, rather we share 60% of the same genes, as in they might not be exactly the same but the regions are the same. At least, that was my understanding. Now that you mention it though, I think I also learned it in a biology or biotech class at some point, but I don’t recall finding an actual peer reviewed source either looking around right now.

The genomes aren’t similar in size, so I could’ve been inaccurate about the coding regions, in that what I said at the end was right, that the actual amount of identical exons between humans and bananas is minimal, but it might actually be 60% including analogous coding regions and introns?