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Carbohidratos. Pruebas cualitativas de identificación. Fehling, Benedict, Lugol. Ejercicio al final! — Transcript

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0:12Howdy, guys! I'm happy to greet you.
0:16Today I bring you a new video to
0:18continue talking about carbohydrates.
0:22Specifically, today we're going to talk
0:24about qualitative identification tests.
0:27Well, I remind you that here on my Gabo
0:29Rosado channel, you'll be able to find
0:31several videos about carbohydrates.
0:34Specifically, I've already uploaded
0:35eight and the one you're watching right
0:37now is number nine. Let's say we're
0:39closing a series of videos about
0:41carbohydrates. We might be able to
0:44upload some extras in the future, but
0:45these nine would already cover the
0:47topic of carbohydrates to a good level,
0:49for me. Okay? In order to understand
0:54number nine, you should have watched
0:56the previous ones, since this one in
0:58particular will use previous concepts,
1:00such as reducing sugars, which are
1:01ketoses, which are aldoses, and the
1:03classification of carbohydrates. Okay.
1:08Well, now let's start with the
1:10qualitative tests for identifying
1:12carbohydrates. It says here, "The
1:16objective of these tests is to observe
1:18the behavior of a series of
1:19carbohydrates by subjecting them to
1:21various qualitative analyses and, based
1:23on these observations, identify the
1:25carbohydrate or carbohydrates present
1:27in an unknown solution. There are
1:30different types of chemical reactions
1:32that allow us to qualitatively
1:34determine the presence of carbohydrates
1:36, whether they are monosaccharides,
1:37oligosaccharides or polysaccharides.
1:40And these reactions are based, for
1:42example, on the reduction of copper or
1:44on the coloration that the sugars take
1:46on after reacting with a reagent. In
1:48other words, all the tests that we are
1:50going to see right now are qualitative,
1:52that is, they will not tell us how much
1:54carbohydrate there is, because those
1:55would be quantitative, but rather they
1:57will tell us what type of carbohydrate
1:59there is in a sample. Okay, and all of
2:01them are based on chemical reactions,
2:03such as, for example, the reduction of
2:06copper is mentioned here, that is, we
2:08are going to work with
2:09oxidation-reduction reactions or also
2:11with colorations, okay? Here it says
2:13colorations that will help us identify
2:15which carbohydrate is present in a
2:17certain sample. Well, let's start with
2:21the First, the Molish test, and this
2:23subjective test has the objective of
2:25identifying carbohydrates in general.
2:29In other words, this test tells you
2:30whether or not what you have in your
2:32sample is a carbohydrate. Well, let's
2:35see how this test works. This test is
2:38based on the hydrolyzing and
2:40dehydrating action of concentrated
2:42sulfuric acid on carbohydrates. In
2:45other words, if I have a carbohydrate
2:47and I add sulfuric acid to it, it will
2:49hydrolyze and dehydrate it. I think the
2:52word dehydrate is very easy, it means
2:54removing water, but the word hydrolyze,
2:57okay? It has another meaning, which is
2:59basically breaking the structure, and
3:01it will break it, okay? Through, in
3:04this case, water, okay? A water
3:08molecule will break the structure and
3:09in the end that water molecule will
3:11dehydrate. Okay, so in fact, if you
3:14look here at the chemical reaction, we
3:16are removing water. Well, so in this
3:20test, the acid What it will do is
3:21hydrolyze any glycosidic bonds present
3:24in the sample and dehydrate the
3:25resulting monosaccharides to form
3:27furfurals. So, we already said that
3:31what sulfuric acid will do is break
3:33down the monosaccharide or disaccharide
3:35or whatever the carbide is, it will
3:37break it down and ultimately dehydrate
3:39it. The furfurals will come out, which
3:43is what will remain after we have done
3:45that dehydration. The furfurals will
3:50react with the alpha-naphthol of the
3:51Molish reagent and will give rise to a
3:53violet-colored product or a ring, okay?
3:57Violet. In this case, guys, if I break
4:00the structure, in this case, look, an
4:03exose, an exose, remember that it is a
4:05carbohydrate or a six-carbon
4:06monosaccharide, when the exose breaks
4:09down and dehydrates, what it will form
4:11is a furfural. In this case, the
4:13furfural that will form is a
4:15hydroxymethyl Furfural. It comes out as
4:17if it were a pentose. When pentoses
4:20break down and dehydrate, what they
4:22form are furfurals. That one is pure.
4:25That is a hydroxymethyl furfural and
4:27that is a furfural. It is an exam
4:29question. For example, the molish test,
4:31an exose, what does it turn into? A
4:34hydromethyl furfural. A pentose, what
4:37does it turn into? A furfural. Now,
4:40these two have furfural characteristics
4:42, okay? And what they are going to do
4:44is react with the two alpha naphthol.
4:48which is this one over here, which is
4:50present in the molish reagent and it is
4:52going to form a colored complex, that
4:53is, the sample is going to be colored
4:55if we are talking about an exose or a
4:57pentose or in particular a carbohydrate
4:59, okay? Whichever way this reaction
5:03takes, it is going to be colored. If it
5:05is not colored, in this case purple, we
5:07are talking about it not being a
5:09carbohydrate. It is that simple. That
5:11is to identify carbohydrates. In
5:12general. Now, let's imagine that you
5:14already know that you have a
5:16carbohydrate, but you don't know what
5:17type of carbohydrate it is. Well, this
5:19is what a vial test is for. What the
5:22vial test does or its objective is to
5:24identify pentoses. It produces a
5:27specific colored reaction for pentoses,
5:29this one in particular. Under carefully
5:32controlled conditions of temperature,
5:34time, and hydrochloric acid
5:36concentration, the pentoses are rapidly
5:38converted to furfural, which is the
5:40same reagent. Okay? Well, it does not
5:44react with the same intermediate that
5:46we obtained here, the furfurals, okay?
5:48Those are the structures that are
5:50ultimately going to be colored. In this
5:52case, here we use sulfuric acid and
5:54here we use hydrochloric acid. The
5:57hydrochloric acid is going to have
5:59practically the same structure or the
6:01same function that it did in the
6:02previous step, okay? It's going to
6:04break down the carbohydrate. That's
6:06what the hydrochloric acid is going to
6:08do and it's going to become, I repeat,
6:10a furfural. Now, How is this different
6:12from the presence of ferric
6:14nicotinamide and orsinol, which is what
6:16makes the vial test characteristic,
6:18okay? In the presence of ferric
6:21nicotinamide, sorry, and orsinol,
6:23furfural condenses rapidly to produce a
6:25green complex upon heating. Therefore,
6:30unlike this one, two alpha naphthol was
6:32used here, which is what gives the
6:34characteristic to the Molish reagent,
6:36okay? But in this, which is the vial
6:39test, what gives it the characteristic
6:41is the ferric nicotinamide and orsinol
6:43that are present in the vial reagent.
6:46That is what will make it turn green
6:47instead of violet. And if your
6:49carbohydrate changes green, what you
6:51will have is a pentose. Which pentose?
6:54It is not known, but you can already
6:55know that it is a pentose and you can
6:57rule out that it is an exose, a triose,
6:59a tetrose. Okay, for now, this is used
7:02to identify pentoses. What color will
7:04it change to? to green, like this one
7:06here or that one over here. Well, there
7:09is another test called the Celof test.
7:11In the Celof test, the objective is to
7:14identify ketoses. Well, in this case,
7:16the colored reaction that allows us to
7:19identify, I repeat here, ketoses in
7:21concentrated hydrochloric acid solution
7:23. Let's say that it's going to be the
7:26same, the same way to start. The
7:28hydrochloric acid is going to break
7:30down, in this case, it's going to
7:32dehydrate, it's going to hydrolyze the
7:34carbohydrates. Well, in concentrated
7:36hydrochloric acid solution, the ketoses
7:38are dehydrated more quickly than the
7:40aldoses. They produce furfural
7:43derivatives. Again, we obtain furfural
7:45that is going to be colored. These
7:48compounds form complexes with the
7:50resorcinol present in the Celanof
7:52reagent. Celanof, unlike the Vial test
7:58or the Vial reagent, is that Bial has
8:00Ferric John and Orsinol that color the
8:03furfural green. On the other hand, in
8:08Celanof, Furfural, okay? That's the
8:10structure that's over here, whether you
8:12have it in hydroxymethyl furfural or in
8:14furfural, okay? It's going to color it
8:19in this case cherry red, because
8:21there's resorcinol in celanof, okay? So
8:26, we've basically already seen that
8:28furfural is going to be colored in
8:30different colors, either violet, okay?
8:34Because of the 2 alpha naphthol, here
8:36it's violet because of the 2 alpha
8:38naphthol, green because of the ferric
8:40ion and orcinol, and cherry red because
8:42of the resorcinol. It works. So, all of
8:45those have to do with furfural and they
8:47all have to do with an acidic medium.
8:50Remember that the first one was with
8:51sulfuric acid and the other two were
8:53with hydrochloric acid. Now, let's go
8:55to the Tollens test. The Tollens test
8:58is used to identify aldoses. Just as
9:01the previous one, which was elovf, was
9:03used to identify ketoses. This one is
9:06used to identify Aldoses. Well, the
9:09basis of this test is the chemical
9:11reaction between Tolens 'reagent,
9:13ammoniacal silver nitrate solution.
9:15That's Tolens' reagent. Well, in fact,
9:18here it is. It's a solution of silver
9:20and ammonia. Well, and an aldehyde. So,
9:23I'm going to start over so we don't
9:25confuse anyone. The basis of this test
9:27is the chemical reaction between Tolens
9:29'reagent, which we already said what it
9:30is, and an aldehyde. Remember that
9:32aldehydes in carbohydrates are in the
9:34form of aldoses, which exposes a silver
9:36mirror on the walls of the container.
9:39Here again we resort to color. If you
9:43notice, that's a reaction for any
9:44aldehyde. Aldeide. Aldege plus Tollens'
9:48reagent will produce a or a silver
9:50mirror formation, okay? And it will
9:54also produce a carboxylic acid. Notice
9:57how here we have a carboxylic acid and
9:59here I have an aldehyde. If I talk
10:02about a Carbohydrate, this one here is
10:04an aldehyde, it is an aldose, it is
10:06glucose. And when we break this, okay?
10:10And it begins to break, it begins to
10:12structure itself, the aldehyde remains
10:14here, this one that is over here. This,
10:17when it comes into contact with, uh,
10:19the ammoniacal solution of silver
10:21nitrate, well, the silver mirror is
10:23formed and also, look here, COOH is
10:25produced, which would be the carboxylic
10:27acid, which would be by that type. This
10:30is the general reaction and that is the
10:32reaction applied to an aldose. So, what
10:35happens if I have an aldose and I put
10:37Tollens 'reagent in it? A silver mirror
10:40should be painted on the container, in
10:42this case in a test tube, in a beaker.
10:45What happens if instead of being an
10:47aldose it is an acetose? Well, if it is
10:50an acetose, that silver mirror will not
10:52form. Here are two examples. Notice how
10:54here there is silver, here there is no
10:55silver. and here is the silver mirror.
10:58The silver mirror refers to the fact
11:00that it will stick to the walls and
11:02will have a very bright color, in this
11:03case silver. Okay, well, that chemical
11:06reaction is very, very interesting.
11:09Let's now move on to the Benedict test,
11:11which is possibly one of the most
11:12important tests for carbohydrates. It
11:15says here, objective: to identify
11:17reducing sugars. In other words, the
11:19Benedict test will tell you whether a
11:21sugar is reducing or not. Okay? It's
11:23that simple. It is one of the main
11:25tests for identifying reducing sugars
11:27in alkaline solutions. These
11:30carbohydrates can reduce copper +2,
11:32which if you look closely has a blue
11:34color, okay? And copper, excuse me,
11:37will reduce it from +2 to +1, which in
11:40this case would be a brick red color.
11:44And this is useful for scientists,
11:46chemists, biochemists, okay? Those who
11:49work in a laboratory to be able to
11:51decide whether the sugar was reducing
11:53or not. In other words, this change
11:55from blue to red is what that will be
11:56useful to you. For example, here I have
11:59a test tube with Benedict's reagent and
12:04a carbohydrate. Here, since there was
12:06no chemical reaction, there was no
12:07reduction reaction, it remained as
12:09copper + 2, which is its characteristic
12:11color, blue. In this red, there was a
12:13chemical reaction, okay? And the copper
12:17from + S2 turned to +1. Now, why does
12:20it turn red? Because the red color is
12:23given to it by this precipitate, that
12:25is, by this solid that appears here,
12:26which is copper oxide one. Copper oxide
12:29one is what makes it look red. Now,
12:31what does Benedict's reagent contain?
12:34It contains copper sulfate. The copper
12:36sulfate here, in this case, copper has
12:38an oxidation number of +2. That's why
12:41we say that in this case the John is +
12:43S do and that's why the little bottle
12:45looks blue. When I add it to my samples
12:46, several things can happen. For
12:47example, if the reaction doesn't take
12:48place because there's no reducing sugar
12:50, it will remain red. For example, if
12:51the reaction doesn't take place because
12:53there's no reducing sugar, it will
12:54remain red. in blue. That is, here we
12:59have a non-reducing sugar, but as I add
13:01reducing sugar to this, that is to say
13:03to the samples, the color changes until
13:06it reaches a brick red color. And if
13:10you notice, here we can identify if we
13:12have a low amount of reducing sugar or
13:14a large amount of reducing sugar based
13:16on the color. This is the concentration
13:18of reducing sugar. If I have zero
13:20reducing sugar, that is to say, I have
13:22no reducing sugar, it will remain blue.
13:24If I have very little reducing sugar,
13:26it will remain green. I increase it a
13:27little more, it becomes yellow, it
13:29becomes orange, until it becomes a
13:31brick red color. The brick red is
13:33indicating, I repeat, the presence of
13:35reducing sugar. And it all has to do, I
13:37repeat, with the oxidation-reduction
13:40process that is handled, I repeat, with
13:42reducing sugars. In this case, the one
13:44that is reduced would be copper from +2
13:46to +1 and the one that is oxidized is a
13:48reduction oxide. The one that is
13:49oxidized would be the carbohydrate.
13:51Okay, let's go with the fel test. Which
13:55is practically, practically The same as
13:57Benedict's, that is, they use the same
13:59principle, which is to identify
14:01reducing sugars, and it is a test very
14:03similar to the Benedict test, it says
14:05so, and it is also one of the main
14:07tests to identify reducing sugars in
14:09alkaline solutions, like the previous
14:11one, okay? These carbohydrates can
14:14reduce copper +2 from a blue color to
14:16copper +1 from a brick red color. That
14:19is, if you do not have Benedict's
14:20reagent in your laboratory, that is,
14:22you do not have Benedict's reagent, you
14:24can buy Felix's reagent or have it
14:25lying around and use it for the same
14:27thing. For what? How does the
14:29experiment consist? It is very simple.
14:31In a test tube, you place Felix's
14:33liquid, that's what it's called, liquor
14:35. You add sugar, in this case, you add
14:38a carbohydrate. You may not know if it
14:40is reducing or not or if it is reducing
14:42, okay? You add a carbohydrate and heat
14:45it. If it changes color to red, it is
14:48reducing. If it does not change color
14:50to red, if it remains blue, it was not
14:52reducing. It's that simple. Okay.
14:55Interesting fact. Feling's reagent
14:57comes in two little bottles. One as
15:00solution A and the other as solution B.
15:02Solution A contains copper sulfate,
15:03which was also used in Benedict's, and
15:05solution Bene contains an alkaline
15:07solution of sodium potassium tartarate.
15:10Okay, it's like a cultural fact. So,
15:14don't forget it. Benedict and Feling do
15:16the same thing, it's the same function.
15:18In fact, they use similar reagents,
15:21okay? They're based on copper and what
15:24they're trying to do is identify
15:26reducing sugars. Let's move on to the
15:29next one that's also related to
15:31reducing sugars, which is the Barfood
15:33test. In this case, the goal is to
15:35differentiate monosaccharides from
15:37reducing disaccharides. In other words,
15:39we're going to be able to use this type
15:41of test to know if what we have is a
15:45monosaccharide or if what we have is a
15:47disaccharide. It says here,"
15:49Monosaccharides rapidly reduce the
15:51copper + 2 of the Barfood reagent to
15:54copper + 1. "Okay, which is basically
15:56it. the same principle that we use for
15:59Benedict and for Efelin, which is to
16:01reduce copper from +2 to +1. Except
16:04that in the case of the BARF reagent,
16:06well, monosaccharides do it or react
16:08very quickly, okay? And let's say that
16:13very quickly is approximately 0 to 6
16:15minutes, which precipitates as copper
16:17oxide plus a, okay? Red in solution to
16:19weak acid. That is, it will take on a
16:23color similar to the one in the photo,
16:25which is more or less the color that I
16:27presented in the previous slides, where
16:28we said it was a brick red color. Okay?
16:31That precipitation is indicating to me
16:33that if it is a carbohydrate, it comes
16:35out, it is a reducing carbohydrate, but
16:37the speed will indicate to me if it is
16:39a monosaccharide or a disaccharide. On
16:42the other hand, disaccharides reduce
16:44copper plus C in a longer time.
16:46Generally, we say that a longer time
16:48would be 7 to 12 minutes or more. There
16:50are carbohydrates that do it in an hour
16:52, for example. Okay? Here we're going
16:55to imagine that it's seven and up. This
16:57test is performed in an acidic medium,
16:59unlike the previous ones. So, let's
17:02establish these rules, okay? If we only
17:04want to identify reducing sugars, it
17:06doesn't matter what type of sugar it is
17:08, as long as it's reducing, you can use
17:10Feling or you can use Benedict. But if
17:14what you want to do is differentiate
17:16between reducing monosaccharides and
17:18reducing disaccharides, you use Barfold
17:20because monosaccharides react quickly,
17:22okay? This red precipitate forms faster
17:26than disaccharides. Therefore, one way
17:29to identify whether it's monosaccharide
17:31or disaccharide is with that test and
17:32with the speed of the reaction, okay?
17:35The faster this color appears, it means
17:37it's a monosaccharide and the later it
17:38will be a disaccharide. And this would
17:42be the last test, it's not the end of
17:43the video, but it's the last test,
17:45which is the Lugol's test. And it says
17:47here that its objective is to identify
17:49polysaccharides. Okay, a test widely
17:51used to detect starch. So, this test is
17:54for polysaccharides, but it is
17:55particularly widely used for starch.
17:58When Lugol's solution, in this case
18:00Lugol's is a solution of iodine and
18:02potassium iodide, comes into contact
18:04with this polysaccharide, I repeat, we
18:06are talking about starch, a complex is
18:09formed between the iodine I3 minus,
18:11which is the hard iodide, and the
18:12amylose molecule of the starch, which
18:15has a helical conformation. When this
18:19hard iodide is introduced into the
18:21helix, it forms a blue or black product
18:23depending on the concentration of the
18:25sugar. Other polysaccharides such as
18:29amylopectin produce a reddish-purple
18:31color and glycogen a reddish-brown
18:33color when in contact with Lugol's.
18:37This test is very simple. You have a
18:39small beaker with your sample. In this
18:41case, you know that it is a
18:42carbohydrate, but you do not know
18:44exactly what type of carbohydrate it is
18:46. Well, you add a few drops of Lugol's,
18:49which has a slightly brown color, like
18:51mustard, as seen here. You add it and
18:55what will happen is that immediately,
18:56okay? There should be a color change to
18:59purple or a little purple or a little
19:01black. That change is indicating the
19:04presence of carbohydrates,
19:06polysaccharides, okay? In particular,
19:09if you look closely, here is an image,
19:12where the pam is. Pam is a food product
19:16that has a high starch content. Look at
19:19the black color that the ugol has here.
19:21The ugol was added in the form of drops
19:22and it turned out this black. Okay? The
19:25same with potatoes, potatoes usually
19:27have a high content of ugol, sorry,
19:29starch and with the ugol it turns
19:31completely black. Here I show you the
19:34helices that this part of this text
19:36talks about. This hard John Trillo is
19:40inserted into the helices, okay? Making
19:43it look like this. When the yom is
19:45inserted inside this helix. Okay, it
19:48turns completely this color. But if you
19:50heat it up, it turns completely black.
19:52or one way to get rid of this yon is to
19:54heat it, we return to the original tone
19:56. Okay, it's something like you have as
19:58data there. Well, to summarize, guys,
20:01we've already seen a lot of tests. I
20:04would like us to have a summary to
20:05fully understand how the part of the
20:07tests works. The first one we saw was
20:10the Molish test and this basically says
20:12that it will identify carbohydrates in
20:14general. That is, if I have a
20:17carbohydrate in a sample and I explain
20:19this, uh, this Molish reagent, what I'm
20:21going to stop is a coloration, okay?
20:25Violet. That is, there will be a purple
20:27ring and that will indicate that the
20:29test is positive and that I have
20:30carbohydrates there. Another test is
20:33the vial test. What the vial test will
20:37do is identify pentoses and pentoses
20:39are green positive, that is, it will be
20:41green if the test is positive. In this
20:46case, it turns green, the color is
20:47indicating that we have a pentose in
20:49the sample. On the other hand, The
20:53SwanOf test is used to identify, sorry,
20:56ketoses, and this type of test is also
20:58by color, and the cherry red color,
21:00okay? It tells me that I have a
21:03positive test, that is, that I have
21:05ketoses in the sample. If it doesn't
21:07change to cherry red, it means that I
21:09don't have ketoses. For the Tollens
21:11test, in this case we have the
21:13identification of aldoses. Let's say
21:15that these two are contrasted. In this
21:18one I can identify the dosas and a
21:19silver mirror will form in the
21:21container. Yes, and only if aldehydes
21:24appear, in this case aldoses in my
21:26sample. We also have the Benedickell
21:29test. These two basically do the same
21:32thing, which is to identify reducing
21:34sugars using in fact the same procedure
21:36, which is using copper sulfate. Well,
21:40what that copper sulfate is going to
21:42contain is copper +2 that is going to
21:44be reduced to copper +1 and when it
21:46makes that reduction change, a brick
21:48red color will appear that will
21:49indicate that the test is positive. And
21:53if the test is positive, it means that
21:55I have reducing sugars. If there is no
21:57change in the color of the sugar, sorry
21:59, to brick red, it means that the sugar
22:01is not reducing. We also have the Barfo
22:05test, and in this case, this test tells
22:07us that we will be able to
22:08differentiate monosaccharides from
22:10disaccharides. This test is also for
22:13reducing sugars. In fact, it uses the
22:15same principle, it uses the principle
22:17of copper reduction. In this case,
22:19there is a color change from red to
22:21brick like the one here, but if it is
22:23fast, the test will be positive for
22:25monosaccharides, and if the color
22:26change is slow, it will be positive for
22:28disaccharides. Well, finally, there is
22:32the Lugol test. This Lugol test helps
22:35us identify polysaccharides. In fact,
22:38one of the polysaccharides that is most
22:40used in this type of test is starch. It
22:43is a test specifically for starch. Uh,
22:47how do I know or how do I recognize
22:49that I have starch in my sample when,
22:51when applying LOL, the color changes to
22:53blue or black, that is, something very
22:55dark. And we have a positive starch
22:58there. I think that's a good summary
23:02that can tell you or help you when
23:03deciding what type of test you need to
23:05identify carbohydrates. And to close
23:10the video, we have here an example or
23:12an exercise that could help you better
23:14understand the topic we just saw in the
23:16video. Okay, it says here," In a
23:20laboratory and a sample in a beaker, it
23:22is suspected that it is a carbohydrate.
23:24"We are not sure, we do not even know
23:26what type of carbohydrate it could be,
23:28but we are going to apply the tests,
23:30okay? Uh, theoretically to see what it
23:32could do. It says here, section A. Then
23:35, molish reagent is added and the color
23:37changes to purple. And the question is,
23:41what does this tell us? Okay, what
23:44could you answer if you add something
23:46you suspect is a carbohydrate to your
23:48sample, you add a molish reagent, you
23:50do the experiment, and it changes color
23:52to purple. What could you conclude?
23:54Well, let's go to section B. To the
23:56same sample, okay? That is, to this one
23:59that we suspect is a carbohydrate in
24:01another one in another beaker or in
24:03another test tube, okay? Something we
24:06take a sample of this carbohydrate or
24:08that suspected carbohydrate and now
24:10instead of applying molish we apply
24:11lugol. And in this case it says that
24:15the color does not change. If we apply
24:17lugol the color changes. What can you
24:20conclude? Okay, section C. The sample
24:24is analyzed again in another beaker and
24:26the barf test is performed, taking a
24:28long time to show any insignificant
24:30change to red color. What can you
24:33deduce from this? Finally, the fel
24:36liquor is added and the test is
24:38negative. Do you remember that it was
24:41negative in felling? Okay, it says the
24:43test is negative. Could you try to
24:46predict what carbohydrate was present
24:48in the sample? That is, from these four
24:52tests, four independent tests on the
24:54same sample, you should be able to say
24:56what type of carbohydrate it is here in
24:58the last section. I would like you to
25:04tell me at the end of the video what
25:06you think is the carbohydrate we are
25:07talking about here. Leave it in your
25:13comments, we will analyze it, discuss
25:15it and in the next video I upload,
25:17which should be the one on proteins, in
25:18fact it is here, there I will surely
25:20talk or I will start the protein video
25:22by talking about the answers to the
25:24previous exercise. Okay, I would like,
25:29I repeat, for you to comment on what
25:31you think is the carbohydrate we were
25:32talking about in the previous exercise
25:34based on what I reviewed in the video.
25:37Okay, guys, I won't take up any more of
25:39your time. Have a great day. I hope the
25:41carbohydrate videos have been useful to
25:42you and I will see you in the protein
25:44videos. Greetings.

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