0:02 Hi everybody, Dr. Mike here. In this
0:04 video, I want to talk about buffers
0:15 [Music]
0:17 Now, buffers resist drastic changes in
0:20 pH. We know that our blood has a pH of
0:24 between 7.35 and 7.45. That's worth
0:28 putting up. pH of 7.35
0:31 to 7.45.
0:34 And if the blood pH goes below 7.35,
0:36 it's becoming too acidic. If it goes
0:38 above, it's becoming too alkalinic. That
0:41 means that the concentration of hydrogen
0:44 ions, which dictates the pH is either
0:47 going to be too much if it goes in this
0:50 direction, too many hydrogen ions, or
0:53 not enough hydrogen ions if it goes in
0:55 this direction. So what happens in the
0:57 body is if we don't have enough hydrogen
0:59 ions, we need to make more. If we do
1:00 have too many hydrogen ions, we need to
1:02 reduce it. And this is what buffers do.
1:06 They resist these drastic changes in pH.
1:08 All right? So for example, I want to
1:10 talk about a quick buffer. And a buffer
1:15 that looks like this H2 CO3.
1:23 And you should know that the definition
1:26 of an acid is anything that can donate a
1:29 hydrogen ion. So that means that this
1:33 carbonic acid can give us a hydrogen
1:35 ion. Now if it does give us a hydrogen
1:36 ion, what are we left with if we take
1:38 one hydrogen out of this? We're left
1:40 with one hydrogen, one carbon, and three
1:43 oxygen, which is H3.
1:46 H3.
1:47 And because we stole a positive from
1:50 this, it's left with a negative. And
1:57 Bicarbonate
2:04 Again, it's the concentration of the
2:06 hydrogen ion that dictates the pH. So
2:16 which donates a small number of hydrogen
2:20 ions and leaves us with a weak base.
2:21 Now the definition of a base is
2:24 something that can mop up hydrogen ions.
2:26 It can bind to hydrogen ions which means
2:29 if that can bind to that this is a
2:32 reversible equation and so this can also
2:33 go in
2:36 this direction. Now what we have here is
2:39 a very simplistic buffer system where if
2:41 we don't have enough hydrogen ions the
2:43 weak acid will split apart and release
2:45 hydrogen ions. If we've got too many it
2:47 will bind to bicarbonate and go in that
2:50 direction. Now our body utilizes this
2:54 reaction but with the addition of some
2:59 other parts. For example, carbon dioxide
3:05 If you bind carbon dioxide and water,
3:08 have a look, there's one carbon, there's
3:10 the one carbon. Two + one oxygen is
3:13 three oxygen. Two hydrogen, two
3:15 hydrogen. If you bind carbon dioxide
3:19 with water, you get carbonic acid. So,
3:20 let's write these down just for
3:23 completion sake. Carbon dioxide
3:29 and water. All right?
3:30 All right?
3:33 And that can split itself apart to
3:35 produce these two. So, that's reversible
3:37 as well. What we've now drawn up here is
3:40 something called the bicarbonate
3:42 buffering system. And this is one of the
3:44 most important biological buffers that
3:46 we have. Now, let me talk about it in
3:48 regards to how it actually works. All
3:51 right, this end of the equation deals
3:54 with the lungs.
3:56 This end of the equation deals with
3:58 predominantly the kidneys. Now, this is
4:00 important because when we look at
4:04 imbalances in regards to pH, we can say
4:07 if something's wrong here, it could be
4:09 metabolic or kidney caused. If
4:11 something's wrong here, then it could be
4:12 respiratory cause. And this is going to
4:14 be the basis of respiratory versus
4:18 metabolic acidosis or alkyossis. Right?
4:19 That's for another lecture. But let's
4:22 think about like this. Let's just say we
4:24 do not have enough hydrogen ions in the
4:26 body. If we don't have enough hydrogen
4:29 ions, the pH is going up. Right? So
4:30 remember, it's a reverse logarithmic
4:32 equation. Have a look at my previous
4:35 video about calculating pH. Right? We
4:37 don't have enough hydrogen ions. How do
4:40 we create more? Let's have a look.
4:43 Carbon dioxide. This is a byproduct of
4:45 respiration. Breathe in oxygen. Our
4:47 mitochondria utilize that oxygen and it
4:50 produces ATP, water, and carbon dioxide.
4:52 And we don't like carbon dioxide. We
4:53 want to breathe it out. But in order to
4:55 go from the cells to our lungs to
4:56 breathe out, it has to go in our
4:58 bloodstream. So when carbon dioxide hops
5:00 in our bloodstream, most of our
5:03 bloodstream's water. Inevitably, all our
5:05 carbon dioxide is going to be binding to
5:08 that water. and it will be producing
5:10 carbonic acid. But because carbonic acid
5:12 is a weak acid, hates itself, splits
5:15 itself apart and produces hydrogen ions.
5:17 Which means one way we can increase the
5:20 concentration of hydrogen in our body is
5:22 through the accumulation of CO2. How can
5:26 we accumulate CO2? I'll show you.
5:28 Hold your breath. If you're holding your
5:29 breath, you're not breathing out. And
5:31 this is what happens. Some individuals
5:33 who do not have a high enough
5:36 concentration of hydrogen ions in their
5:38 blood, they may be holding their breath
5:40 a little bit. Their breathing will be
5:43 different. Let's think of it flipped.
5:46 What if we have too many hydrogen ions?
5:48 Well, if we have too many, the
5:51 bicarbonate will mop it up and produce
5:54 carbonic acid, which will then split up
5:57 and produce water and carbon dioxide. So
6:00 if we are acidic and our pH is too low
6:02 because we have too many hydrogen ions,
6:04 we end up producing more carbon dioxide
6:06 which means the patient may breathe more.
6:09 more.
6:12 So the respiration can be an indication
6:15 of the blood pH. And you can also see if
6:17 we don't have enough hydrogen ions, it
6:19 goes in this direction. If we have too
6:21 many, it goes in this. And this is the
