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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

2. Chemical Components of Cells

Acids, Bases, and Buffers


Acids, Bases, and Buffers

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Hi in this video we're gonna be talking about acid spaces and buffers. So assets and bases are molecules found in cellular acquia solutions. Now these are things that you talked about before in your intro Biology and chemistry classes but we're just gonna very quickly review them what it means for cell biology. So first assets are substances that release positively charged hydrogen ions into solution. So the hydrogen gives up its electron for some reason for some type of reaction. Um leaving a positively charged proton in the solution. Um so hydrogen ions then can form uh interactions with water to create a church 30. Which is called a hydro knee um, ion. Now there can be strong acids and there can be weak acids And the difference is that weak acids actually do not completely dissociate in solution where strong acids will um leaving their hydrogen um to be floating around with this positive, this very strong positive charge. Now, bases are substances that um that accept positively charged hydrogen ion. So acids release hydrogen into solution and bases accept them. And so um like acids, there are strong and weak bases and weak base is only partially associate in solution. Um we talk about water a lot. So water actually can act as an acid or a base. Um and it's not necessarily important that you understand different situations in which that happens. We can talk about them as the class moves on. Just know that, you know if you get a question is water and acid or base. So it's kind of a trick question because it can act as both. So um here we have this acid in this water solution and you can see that it's sort of just floating around it has this hydrogen ion. And then when it's put into water um this solution becomes acidic because it releases these hydrogen. Now a base you can see has these um what we haven't talked about with their hydroxide. These are actually called hydroxide but their O. H molecules. So when they are released um into water they can release these oh H. And what does H plus and O. H. Negative make H +20. Which you can imagine forms very easily and can take up these hydrogen atoms um in solution. So acidic solutions have high H Plus and basic solutions have high O. H minus. Um so that they can take up the hydrogen atoms. Now we measure acidity through this ph scale and I and I know that you have seen this before but um you can see here that it's going through ph is measured 0 to 14. It's a log rhythmic scale and it measures the concentration of hydrogen ions, the hydro ni um ion. So H 30. So here you can see that all of this over here is very acidic. It has what we turn a low ph um here at seven it's going to be neutral and this is generally where water resides a lot. And then from, you know 8 to 14 we have this basic and you can see that the color is actually becoming stronger because as you as the ph gets larger for basic or smaller for acidic, it also becomes stronger. So a ph of one is gonna be a really strong acid, whereas a ph of six is gonna be a weak acid. Now, what does this mean in cells well in cells um there are these um different organelles in different compartments that cells have in them and they all have different phs. So in the side of saul which usually averages about a ph of 7.2, um you can imagine this is really a neutral ph in the side of the wall. Whereas if we look at in the list zone it has a very acidic Ph at 4.5. And we'll talk about why this is important. But remember the license um is important for breaking down and destroying materials. You can imagine why um an acid compartment would be really important if you wanted to destroy a lot of materials. We talked about acid and basis. So let's talk about buffers. And so buffers are solutions that limit changes in the ph of a solution. So they're composed of both weak acids and weak bases that can either accept hydrogen ions or release hydrogen ions as the ph tries to change. And so when the ph is trying to change by either accepting those or releasing them, they can adjust the ph um and really keep changes to a minimum. Now, buffers are crucial in cell biology because they are super important in keeping various cellular compartments or various tissues, a certain ph that it has to be for its function. And so one of the best ways to do this is through blood. So blood ph has to be a very specific ph and it's balanced by this week carbonic acid and a weak conjugate base. So as hydrogen um are introduced or taken up into by the blood, the pH tries to change and it can't because you have these weak carbonic acids um um which you can see here and these weak conjugate bases which you can see here sort of taking up and releasing these hydrogen. Now you don't need to know this chemical reaction, You don't need to know these steps. Just sort of understand that these ph processes and buffers are really working in our body all the time to keep everything functioning normally. So now let's move on

Choose which of the following is false.


A substance with a pH of 3 is considered what?


Bases release positively charged ions into a solution?