Wikipedia:Reference desk/Archives/Science/2018 August 1

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August 1

Why is blood pH 7.4

I can’t find this in Wiki;

What makes (human) blood alkaline?

I would have thought dissolved CO₂ would result in an acidic level.

It seems being alkaline helps prevent disease, and hinders cancer, but what makes it alkaline? One article says breathing too slowly (shallowly) lowers pH, breathing too fast (hyperventilating) raises pH - implying that Oxygen raises pH.

So does that mean pH in veins is significantly lower than in arteries? Does pH vary with hunger - ie how long since you’ve eaten? MBG02 (talk) 04:34, 1 August 2018 (UTC)

Our article Acid–base homeostasis contains some discussion of this. Double sharp (talk) 05:56, 1 August 2018 (UTC)

Breathing faster acts to raise pH because you're getting rid of CO₂. A lower respiratory rate lowers pH because you're retaining CO₂. It's not about the oxygen. Venous pH and arterial pH generally agree very closely ( one study showed aterial mean of 7.384 and venous mean of 7.369. [1] - Nunh-huh 07:21, 1 August 2018 (UTC)

Blood is kept alkaline by a whole bunch of body mechanisms, as detailed in the aforementioned article. Your blood contains chemical buffers that automatically compensate against changes in the blood composition that would otherwise significantly change its pH. The body also monitors blood pH, and can alter the blood composition if needed. As mentioned, this means blood pH is almost identical throughout the body, despite differences in blood composition.

As to why, well, the straightforward answer is given in acid–base homeostasis: your body's components stop working properly if the pH changes significantly. You stated, It seems being alkaline helps prevent disease, and hinders cancer. What are you basing this on? It sounds like you might have read some alkaline diet nonsense. Cancer cells do usually produce a more acidic microenvironment, but this does not automatically mean the increased acidity causes cancer. For the ultimate cause, I recall reading somewhere that it's believed because life on Earth first emerged in alkaline oceans, cells are adapted to an alkaline environment, which makes this a kind of evolutionary path dependence, but I'm not sure how well-supported that hypothesis is. Anyone know of some sources discussing this? --47.146.63.87 (talk) 07:52, 1 August 2018 (UTC)

Thanks for your answer, I think the disease/cancer/alkaline diet point was important. About your last question, an interesting question is whether the blood pH is reflective of intracellular pH. I found [2] which says cytosolic pH is nearly neutral, and also some other organelles. Look at this source, it seems it was taken as 7.2 [3]. Something similar is also mentioned in Cytosol, in particular giving a range of 7.0-7.4 in humans. (I missed it since I was earlier searching for info related to you suggestion and was getting a lot of alkaline diet etc nonsense so changed to Google Scholar.) This source suggests 7.4 may be a little high to reflect conditions in most species [4]. Maybe also of minor interest [5] [6] Nil Einne (talk) 18:50, 1 August 2018 (UTC)

The body made CO₂ as a waste product which would tend to make plasma acidic; however, the kidneys make bicarbonate, and plenty of it ... at around 25mM in the plasma, that's the second-most prevalent anion. Klbrain (talk) 23:34, 1 August 2018 (UTC)

In brief, CO2 + H2O <-> H2CO3 <-> H+ + HCO3- <-> 2 H+ + CO₃^2-. The bicarbonate buffer can accept large amounts of acid or base and change only slightly in pH; hence the body can set it to pretty much whatever pH it wants, then keep that pH in the face of minor metabolic adversity (enough pushing on it and eventually you get to acidosis or alkalosis anyway). (Lab chemists do the same, adding drops of acid or base to get the buffer to the pH they want) Note that CO2 gas per se doesn't affect pH; it's only when it interacts with water. But if it's dissolved in water it will interact with water. I think 70% of the CO2 is as bicarbonate and 10% as dissolved gas, but I may not remember that right. (Some sticks to carboxyhemoglobin) Note all the proteins in blood and even in blood cells also have a buffering effect on pH. Wnt (talk) 00:31, 2 August 2018 (UTC)

One minor quibble with the above answer; "the body can set it to pretty much whatever pH it wants" isn't really all that true. All buffer solutions have two measurements that determine the pH range over which they can be effective, and "any pH it wants" is far too broad. The pH range is determined by 1) the equivalence point of the buffer in question (see Henderson–Hasselbalch equation); which is where the pH of the buffer equals the pKa of the acid form; this defines the center of the effective range. 2) The concentrations of the buffers in question, known as the "buffer capacity", which determines the size of the pH range around that center point where the buffer will still, you know, buffer. The effective pKa of the CO2/Carbonic Acid system is about 6ish, and the concentrations in the blood are fairly low, which means that at 7.4, our buffer system is already probably nearing the limits of its truly effective range. I would be shocked if you could push the equilibrium pH to past 8 or so before the buffer broke down. Otherwise, however Wnt's answer is solid. BTW, the Henderson–Hasselbalch equation article contains a nice use of the equation to calculate physiologic pH. --Jayron32 12:40, 2 August 2018 (UTC)

Sorry yeah, I meant, within reason, without killing yourself. ;) Though if you were feeling adventurous you could use the same ions (minus H+) for a carbonate buffer between 9.2 and 10.6 or so. Anyway, I should have linked to a readable source like [7] which also mentions there is a phosphate component to the buffer at lower pH. (Well, it looks readable to me; if that isn't readable to the OP I can try again) Proteins also should provide some buffering capacity over a wide range of pH because there are so many different groups involved. Wnt (talk) 09:20, 4 August 2018 (UTC)

Botany: Can you help me identify this plant spotted in my mum's garden in Switzerland?

My mother has found a plant in her garden that she can't identify. It is located in Switzerland, in the countryside, altitude 635 meters. The plant seems to attract a lot of insects: bees, wasps, rose chafers... Photos available in the links below.

Picture 1 Picture 2 31.35.194.25 (talk) 09:12, 1 August 2018 (UTC)

I'm more familiar with North American plants, but my two best guesses so far are Angelica and Heracleum (Hogweed), though not any specific species I can find. Still looking. --Jayron32 11:07, 1 August 2018 (UTC)

Cicuta and other similar genuses (Hemlocks) maybe also and maybe Cicely. Broadly, the flowering and shape reminds me of many of the plants in the Apiaceae, or Carrot/Parsnip/Parsley/Celery family, which I think includes all of the ones I cited above. There are literally hundreds of species in that family, many of which are familiar vegetables, herbs, or spices like Anise, fennel, coriander, etc. There are also poisonous ones (like Hemlock and Hogweed). Sorry I can't get closer than that, but that's the best I've got there. Maybe a real botanist will be along shortly to help... --Jayron32 11:13, 1 August 2018 (UTC)

Mystery solved: it's a Seseli gummiferum, a.k.a. moon carrot! OP.80.94.146.48 (talk) 07:28, 3 August 2018 (UTC)

July 2018 lunar eclipse - visibility

I would like to know if the visibility map is correct. The visibility map was posted in 2014 for a 2018 lunar eclipse. Article says no visibility in north america. I live in southern California, and I was able to see the lunar eclipse. See July 2018 lunar eclipse#Visibility. link to image

SWP13 (talk) 13:06, 1 August 2018 (UTC)

That visibility map looks correct to me in that it matches what I have seen published elsewhere and (WP:OR here) it agrees with real-time reports from friends in Europe who watched the latter half of the eclipse and reported it ending a few hours before I saw a beautiful non-eclipsed (post eclipse) full moon rise on the East Coast of the US, which should have been a couple of hours before you would have been able to see the moon in California. What did you see that led you to believe you were viewing the eclipse? Might you have seen a cloud block part of the moon making it appear partially eclipsed, or perhaps a haze obscured moon creating the blood moon appearance of the fully eclipsed moon? -- ToE 13:37, 1 August 2018 (UTC)

Just to note that while a lunar eclipse often causes a blood red color for the moon, it is not the only thing which can cause it, so if our Californian above saw a red moon, it doesn't necessarily mean he saw any of the eclipse. This article explains some of the causes of a red moon, only one of which is the eclipse. The moon could be red because it's low on the horizon (the same reason sunsents are red!). Or it could be red because of certain particulate matter in the atmosphere; that article specifically notes forest fires as a possible source of red coloration to the moon. Smog could be another, both of which California has in abundance right now. --Jayron32 14:27, 1 August 2018 (UTC)

>To clarify.. The orange color full moon that I saw was at 8:05pm PDT. The sky was very clear with no smog or clouds. At about 10pm PDT, the moon was very bright white. How does a person distinguish it from the lunar eclipse if the images look so similar? Red Moon article was very helpful. Thank you for confirming the correctness if the visibility map. SWP13 (talk) 22:45, 2 August 2018 (UTC)

An eclipsed moon isn't only red, but also very dim. Judging from the settings I had to use on my camera, this time at 20:46 UTC about 1/7000 of the brightness of a normal full moon. It's a bit variable. At 20:05 PDT, the moon was very low in the sky in California. Add a bit of smoke or dust close to the horizon (which can still be more than 100 km away from you) and you get a red moon. PiusImpavidus (talk) 09:37, 3 August 2018 (UTC)

This should have its own header. I should note that the darkening of the sun, the rending of a curtain, even the exhumation of corpses is consistent with a haboob (sandstorm) which certainly seems within the range of possibility. Such a thing can be seen as symbolic without requiring any departure from normal physics. Wnt (talk) 11:51, 3 August 2018 (UTC)

I only found out yesterday that the phrase "blood moon" is Biblical.

Acts 2.20: The sun shall be turned into darkness, and the moon into blood, before that great and notable day of the Lord come:

The day after the eclipse the Daily Telegraph noted:

The moon was expected to be rendered an even deeper shade of red as a result of dust thrown into the atmosphere by recent volcanic eruptions in Hawaii and Guatemala.

Southern California is comparatively near to these places. 95.150.52.197 (talk) 09:59, 8 August 2018 (UTC)

Why do flies often walk in a saltatory manner? (at least the species I see)

Sagittarian Milky Way (talk) 17:32, 1 August 2018 (UTC)

Wikipedia has articles titled terrestrial locomotion, gait, and jumping which will give you a starting point for you to research your question. If you don't find the answers in those articles, you can use those terms combined with words like "fly" or "walking" in google to find articles. For example, by typing "fly walking gait" into Google, and searching through some of the results, I came up with this article, which seems by the title to directly address your question. In the future, to get faster results when researching, try those techniques (reading Wikipedia articles, following links from Wikipedia articles, playing around with search terms in Google) and you're more likely to get good results. --Jayron32 18:11, 1 August 2018 (UTC)

It is related to the Square–cube law. It takes very little energy to accelerate and decelerate a fly. Therefore, it can quickly move from where it is to where it wants to be. Humans, in relation, require a lot of energy to move from one place to another. So, we appear to move in slow motion in comparison. If you speed up human movement, it will appear as jerky movements from one place to another. You can increase that to elephants, which appear to move slow compared to humans. 209.149.113.5 (talk) 18:22, 1 August 2018 (UTC)

Saltatory (adj) is from Latin saltatio "dance, hop, leap". Flies tend to fly in straight lines interrupted by sudden directional changes that typically involve an angle change of 90° achieved in 50 milliseconds. It is likely that the same rapid reflexes operate when the fly walks and is at heightened risk from predators and Sagittarian's flyswatter. Fish recognize insects as prey by their characteristic leaping pattern of short movements and pauses. DroneB (talk) 18:29, 1 August 2018 (UTC)

We dummies might need the Wiktionary definition for saltatory. 2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 02:32, 2 August 2018 (UTC)

• The motor control system in insects is quite a bit less sophisticated than the system in vertebrates. Vertebrates have a huge brain structure called the cerebellum that acts to smooth out movements (among many other things). Insects have no comparable structure -- it's more a matter of switching motor patterns discretely on or off. This makes their movements tend to look jerky. Looie496 (talk) 12:57, 2 August 2018 (UTC)

That's certainly incorrect. The previous replies are largely on target. Abductive (reasoning) 05:14, 3 August 2018 (UTC)

You seem to be right, ants and roaches don't act like their senses work better while stationary. Though if the monocular/binocular zone makes a German cockroach nervous one/two antenna(s) stop jiggling. I've always wondered if smelling through that taxes its brain. You can use this trick to control cockroach antennas like a light switch. Sagittarian Milky Way (talk) 06:05, 3 August 2018 (UTC)

Insect motions are smooth at the level of individual wing beats or steps. Their jerky movements are on the several body length scale, and are no different than a squirrel, say, avoiding predation while looking for food. Abductive (reasoning) 07:12, 3 August 2018 (UTC)

Well, sort of: the actual patterns of movement involved are drastically different, but you are 100% correct to notate Looie's response as factually incorrect to its core; the motor functions of insects are not in any sense "less sophisticated" than those of vertebrates, broadly; they are in fact highly sophisticated, but simply tailored by selective pressures to a different ecological niche than those of larger organisms. In fact, for virtually all species, much of the insect brain is devoted to locomotion and to integrating movement with sensory triggers to produce the kinds of lightning fast responses many species are capable of in their mature developmental stages. Looie's apparent assumption/speculation that smaller organisms = smaller brains in absolute terms = per se "more simple" behaviours is just categorically false, and particularly not true with regard to relative complexity of motor function between different broad taxonomical categories of organisms. To illustrate the deep complexity of invertebrate motor capabilities, here is one of my favourite pieces of research on the topic to come out in recent years (for those who don't have access through a gateway or are just looking for the highlights, here is the lay coverage, though note that the Post's pop science journalist covering the story also routinely uses terms like "simple insect behaviours" that are not at all consistent with the actual research, which helps to underscore how these pervasive canards are perpetuated). Snow ^{let's rap} 23:27, 4 August 2018 (UTC)

Comment. Crabs walk sideways. Bus stop (talk) 23:54, 4 August 2018 (UTC)