Chemical Buffer Systems – Acid-base Balance (Nursing)

00:01 So our chemical buffer systems are going to rely on the the properties of acids and bases.

00:09 So strong acids dissociate completely when they're in water.

00:13 So therefore, a strong acid will dramatically affect a pH.

00:20 Weak acids, however, only dissociate partially when placed in water.

00:24 And so they are efficient at preventing dramatic pH changes.

00:30 Strong bases are going to dissociate easily in water and they are going to tie up or hold on to H+ ions.

00:41 Weak bases accept these H+ ions more slowly and again prevent dramatic changes in pH.

00:51 So again, a strong acid like hydrochloric acid is going to dissociate completely into H+ and Cl- thus increasing the H+ concentration, or decreasing the pH.

01:07 However, a weak acid such as carbonic acid does not dissociate completely.

01:14 So if you're going to get some H+ ions as well as some bicarbonate ions, but some of the carbonic acid will remain.

01:24 This is going to cause a less dramatic change in the overall pH of your solution.

01:32 So a chemical buffer system is a system where one or more compounds are going to act to resist these pH changes.

01:41 This resisting of a pH change is referred to as a buffer.

01:45 And this is going to do this when a strong acid or a strong base is added to the buffer system.

01:54 There are three major buffering systems found on our bodies.

01:57 We have the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system.

02:05 A chemical buffer will bind to the H+ if our pH drops and becomes too acidic, or it will release H+ if our pH rises and becomes too alkaline.

02:18 So a mixture of carbonic acid which is a weak acid, and salts of our bicarbonate make up are bicarbonate buffer system.

02:29 This includes things like sodium bicarbonate, which is a weak base.

02:34 This is going to buffer both the intracellular fluid and the extracellular fluid, but it's only important in the buffering of our extracellular fluid compartment.

02:46 So what happens in the bicarbonate system, if a strong acid is added? If it is added, then the bicarbonate will tie up the H+ and form carbonic acid.

03:01 The pH will decrease only slightly unless all of the bicarbonate gets used up.

03:07 so if we use up all of our alkaline reserve.

03:11 Their bicarbonate levels in our body, however, are going to be closely regulated by our kidneys.

03:19 In the bicarbonate buffer system if a strong base is added this is going to cause the carbonic acid to dissociate and donate its H+ ions, so that it can decrease the pH.

03:35 The pH will rise only slightly.

03:39 The H+ ions are going to tie up the base for example, it will tie up hydroxide ions.

03:46 And also in this case, the carbonic acid can supply an almost limitless amount of carbonic acid.

03:55 And this can be subject to respiratory controls.

03:59 Another buffer system in our body is the phosphate buffer system.

04:05 The way the phosphate buffer system works is almost identical to how the bicarbonate buffer system works.

04:12 The components are going to be sodium salts of dihydrogen phosphate, which is a weak acid and monohydrogen phosphate, which is a weak base.

04:22 This is actually going to be an unimportant buffering system in our plasma.

04:27 But it's more effective in buffering the urine as well as our intracellular fluid compartments.

04:33 Where we're going to find our highest phosphate concentrations.

04:39 So in the phosphate buffer system, H+ that is released by our strong acids will be tied up with a weak acid.

04:49 Conversely, strong bases are going to be converted to weak bases in this buffer system.

04:58 Intracellular proteins are the most plentiful and powerful of our buffers.

05:04 So this brings us to our third buffer system which is the protein buffer system.

05:10 Protein molecules are amphoteric, which means they can function as both a weak acid or weak base.

05:17 So when the pH rises or becomes too basic, the organic acid or carboxyl groups can release their H+ ion.

05:27 However, when the pH falls or becomes too acidic, the amino group on the protein can bind to the excess amounts of H+.

05:38 Hemoglobin is an also a protein buffer system and can function as an intracellular buffer inside of our red blood cells.