YT YouTube2Text

YouTube2Text → Transcripts → BIOQUÍMICA 3ER PARCIAL Aminoacidos 26 08 25

BIOQUÍMICA 3ER PARCIAL Aminoacidos 26 08 25 — Transcript

by Teóricas de 3er año · 5,292 words · 897 segments · language en · Watch on YouTube

Open in transcriber Summarize with AI Download SRT/VTT

Full transcript

0:01Hello, can you hear me? Let me know if
0:05you can hear me, please. Yes, doctor.
0:11Yes, we can hear you.
0:12Oh, okay. Perfect. Let's continue. So,
0:17since no one was answering, I thought,
0:18maybe it's not coming through well. We
0:27are looking at the catabolism of amino
0:30acid carbon skeletons, and we had said
0:33that the first thing amino acids do is
0:36lose their nitrogenous group, which
0:39becomes urea, and the rest are carbon
0:42skeletons that incorporate into keto
0:45acids or turn into specialized
0:47compounds. So they can lose their group
0:53, becoming oxidized hydrocarbons,
0:55degrading into amphibolic intermediates
0:58through reactions very similar to
1:00branched lipids, and each amino acid
1:02forms an amphibolic intermediate,
1:05particularly in the Krebs cycle. Here
1:10we have different amino acids that are
1:12incorporated into the different members
1:14of the Krebs cycle. The most important
1:17one, and the one that is always asked
1:19about, is alpha-ketoglutarate.
1:22Glutamate, and through glutamate,
1:24arginine and others here, are converted
1:26into glutamate, and glutamate is
1:28converted into alpha-ketoglutarate and
1:30incorporated directly into the Krebs
1:33cycle, giving us the idea that amino
1:35acids will participate via oxaloacetate
1:37in what will...
1:40Yes. Uh, you're not sharing your screen
1:43.
1:46Is it not visible or what? Let's see.
1:49Uh, what you're presenting is not
1:52visible.
1:53Let me go back to the beginning. Now
2:00it's visible. Now it's visible.
2:08Mm. It still isn't appearing for me,
2:10doctor.
2:12Let's see. It's not visible there
2:18either. One moment, please wait for me.
3:57Uh, tell me now if it's being shared,
4:00please. Yes, it's visible, doctor.
4:05Okay, let's continue. So, we had said
4:09that the carbon skeletons of the amino
4:12acids would be converted into Krebs
4:14cycle products, particularly as keto
4:17acids, and others turn into specialized
4:20compounds that interest us quite a lot.
4:23This is where we left off. Tell me now
4:26if it's visible, please. Glutamate is
4:29converted into alpha-ketoglutarate.
4:33Phenylalanine and tyrosine are
4:34converted into fumarate. Are we there?
4:37It's visible. Tell me if it's visible,
4:45please. Hello?
4:52Yes, doctor, it is visible.
4:53Ah, okay. Fantastic. Right. Uh, amino
4:58acids have many functions; they are
5:00very versatile, and one of the most
5:02important functions is to join together
5:04to form proteins, peptides, and
5:06polypeptides. Another form is part of
5:11phospholipids; we have
5:12phosphatidylserine, which is the amino
5:15acid that will generate this
5:17phospholipid that will act as a signal
5:19precursor. Others contribute
5:24nitrogenous groups; others serve to
5:26transport nitrogen, as written; others,
5:29to become specialized products that do
5:31interest us, those not only in the role
5:34of forming protein, but forming heme,
5:37creatinine, purines, pyrimidines,
5:39polyamines, nitric oxide, etcetera,
5:42which are very, very specific compounds
5:44derived from amino acids. Let's see how
5:49amino acids are converted into
5:51specialized products. So, we have
5:54glycine. Glycine is one of the simplest
5:58amino acids that exist. Glycine has a
6:01hydrogen group as an R group, and
6:04glycine participates in the synthesis
6:07of heme. One must remember that heme is
6:11a porphyrin and heme will serve to form
6:14hemoproteins. Glycine, glycine together
6:19with succinyl-CoA forms heme, and heme
6:22is therefore implicit in everything
6:25that will be oxygen transport or
6:27electron movement, and it comes thanks
6:30to glycine. Glycine participates in
6:33purines, there is no doubt about it.
6:36The purines adenine and guanine need
6:39glycine in their composition as donors
6:41of carbon and nitrogen. Glycine is part
6:46of glutathione; if there is something
6:49to remember, it is glutathione, and
6:51glutathione is a tripeptide. It is a
6:55compound that is formed in many cells,
6:57but particularly in the liver. And
7:00glutathione serves to regenerate
7:03cysteine. And glutathione, through the
7:07enzyme glutathione peroxidase, gets rid
7:09of hydrogen peroxides. Therefore, it is
7:14a first-line antioxidant; when the
7:16liver is failing, in cases of renal
7:19insufficiency, or when its functions
7:21are very, very poor, as a doctor, one
7:24prescribes glutathione to the patient
7:27to be consumed as an extra supplement.
7:32Glutathione is essential to avoid
7:34greater damage to the liver caused by
7:37free radicals and also particularly for
7:39the erythrocyte. The erythrocyte, if it
7:44does not have glutathione, undergoes
7:47hemolysis, and hemolysis occurs
7:49constantly due to the absence of
7:51glutathione; glycine serves to
7:54conjugate particularly with bile acids.
7:58If it joins with cholic bile acid, it
8:00forms glycocholic acid. And if it joins
8:03with chenodeoxycholic bile acid, it
8:06forms glycochenodeoxycholic acid, which
8:10are primary bile acids. It will also
8:13form hippuric acid, which is not of
8:14much importance in our environment, but
8:16it serves for conjugation. Synthesis of
8:19creatinine. Glycine is also immersed in
8:21this. Glycine will participate in
8:24creatine. Creatine will later be
8:27converted into creatinine and will
8:29serve as a biological marker compound
8:32for renal function, created in the
8:34liver, kidney, and muscle. So, notice,
8:37glycine, such a simple amino acid, has
8:40many roles. The other thing not
8:43mentioned here, but worth noting and
8:46remembering, is that they are part of
8:48collagen. Every three amino acids in
8:52collagen—remember, there are 20 types
8:54of collagen. In almost all types of
8:57collagen, in fact, in all types of
8:59collagen, glycine participates. Of
9:02every three amino acids in collagen,
9:04one of them is glycine. Therefore,
9:08glycine is also involved in collagen
9:11synthesis. Alanine will form
9:14pantothenic acid. It must be remembered
9:17that we do not produce pantothenic acid
9:19ourselves. Pantothenic acid is a
9:22vitamin that gives rise to coenzyme A,
9:26but in nature, it is formed from
9:30alanine, and alanine also forms acetate
9:34and pyruvate. Remember that pyruvate is
9:38the final product of glucose catabolism
9:41, or glycolysis. So, alanine is also an
9:45important amino acid, and another of
9:47its features is that it is one of the
9:50fastest amino acids. That is, alanine
9:54can very quickly travel from the
9:56intestine to the liver after its
9:59absorption. It is one of the amino
10:02acids that reaches the liver the
10:04fastest. Well, we have serine. Serine,
10:10as we said, will be part of sphingosine
10:13. Sphingosine is an amino alcohol that
10:17will be a specific part of
10:18phospholipids, and sphingosine is found
10:21in large quantities in a component
10:23called sphingomyelin. Serine will also
10:27participate in the synthesis of purines
10:29and pyrimidines. So, we can see how
10:32versatile amino acids are and that they
10:35don't just serve to form proteins.
10:38Methionine is the methyl donor par
10:41excellence. Methionine owes its name
10:45precisely to methyls because in its
10:47composition its R group is a methyl,
10:50and methionine will be incorporated
10:52into many chemical compounds through
10:55methyl donation, a process called
10:57methylation. One of the compounds that
11:02needs to be methylated and demethylated
11:05to function properly is DNA, which,
11:07thanks to methionine and other methyl
11:09donors, is capable of being methylated
11:12or demethylated. But anyway, in this
11:15case, methionine is a methyl donor, and
11:17that is what interests us a lot.
11:20Cysteine is an amino acid that, as
11:22mentioned, will be part of glutathione.
11:27It will also participate in the
11:29formation of coenzyme A and urinary
11:31sulfate. Don't forget that cysteine
11:36provides us with sulfur, and the source
11:38of sulfur we have in our body is thanks
11:40to cysteine. Cysteine has two sulfur
11:44molecules and usually uses one of them
11:47to bind with another cysteine and form
11:49a disulfide bond. Histidine forms a
11:54biogenic amine that is extraordinarily
11:57important in allergic reactions, which
12:00is called histamine. It is formed
12:03thanks to a single enzyme. Histidine is
12:05easily converted by histidine
12:07decarboxylase. Histamine is stored in
12:12mast cells and also in basophils. And
12:17at the moment an allergic reaction
12:19occurs, it is released from storage
12:20granules. It also gives rise to other
12:23compounds such as carnosine. Aspartic
12:27acid, or aspartate, will participate in
12:29the formation of pyrimidines. We must
12:33remember that pyrimidines are, like
12:35purines, important compounds for the
12:37synthesis of nucleic acids. And there
12:41we have cytosine, thymine, and uracil,
12:43which need aspartate or aspartic acid
12:46for their formation. Valine will form
12:51part of pantothenic acid. Notice the
12:54importance of pantothenic acid. A
12:55molecule that gives rise to coenzyme A,
12:58it has many amino acids that converge
13:00within it. Penicillin, which is a
13:04fungus that will later serve to treat
13:07microbes, is an antibiotic. It also has
13:11valine in its composition. Lysine will
13:13be found in other compounds, cadaverine
13:16and anabasine. Tryptophan is another
13:19important amino acid. Tryptophan is the
13:22largest amino acid we have and it is of
13:24great interest because it forms
13:26serotonin. Serotonin is also a biogenic
13:29amine. And serotonin will act as a
13:33neurotransmitter that will be involved,
13:36particularly in depression, mood,
13:39wakefulness, sleep, depression, and so
13:43on. When there are cells, particularly
13:46intestinal cells, that produce a lot of
13:49serotonin, the disease is called
13:52carcinoid disease. It is not cancer, it
13:55has nothing to do with cancer, but the
13:58word "carcinoid" was imposed due to a
14:00relationship and a misidentification
14:02over a century ago, and it remained as
14:04carcinoid disease, but it has nothing
14:06to do with cancer. Serotonin in the
14:10intestine, I repeat, gives rise to a
14:12disease that, due to excess serotonin,
14:15is called carcinoid disease, which
14:17particularly occurs in the appendix or
14:19other parts of the intestine. It can
14:22also be found in the bronchi, but it is
14:24primarily at the intestinal level.
14:27Tryptophan gives rise to nicotinic acid
14:29or NAD. NAD, do not forget, is a
14:34coenzyme derived from this vitamin,
14:36which is niacin or nicotinic acid, and
14:39NAD will act as a coenzyme that will
14:42transport reducing equivalents or
14:44hydrogens to the respiratory chain for
14:47energy generation. Tryptophan will form
14:52melatonin. Melatonin has been heavily
14:56hyped over the last 10 or more years as
14:59a specific sleep hormone, a happiness
15:01hormone, and so on. And it was believed
15:05that melatonin was produced exclusively
15:07in the pineal gland. Today it is known
15:11that wherever there is tryptophan,
15:13melatonin is produced, and there is
15:14tryptophan in all cells, I repeat,
15:16particularly at the level of intestinal
15:18, bronchial, and other cells.
15:21Indoleacetic acid has very little, uh,
15:24reference, rather it is a precursor of
15:27compounds that are formed from
15:30tryptophan. Tyrosine, tyrosine is
15:33another of the important amino acids.
15:37Tyrosine will form the skin pigment
15:40that is called melanin. People who have
15:44the disease of albinism lack an enzyme
15:47that converts tyrosine into melanin. It
15:51is a congenital disease that is seen,
15:53uh, relatively commonly in some parts
15:55of the world, it is not particularly
15:57everywhere. Where it is seen most
16:00curiously is in Africa. Africa has a
16:03black population per se, but from time
16:06to time albinos are born and it is a
16:08congenital deficiency of tyrosine, of
16:11tyrosinase, which is what it's called,
16:13and the pigment melanin is not produced
16:16. The pigments as such are not there,
16:21even though the melanin granules are
16:23present and even though the
16:24melanocyte-stimulating hormone is
16:26present, this pigment is not formed and
16:29the person acquires a white color,
16:31including the irises, which cease to
16:33have color. Tyrosine will form
16:37catecholamines and that matters a lot
16:39to us because without catecholamines we
16:41cannot live. The catecholamines are
16:45dopamine, noradrenaline, and adrenaline
16:48in our body. Obviously, they have a
16:51precursor which is dopa, but they are
16:53formed and the catecholamines regulate
16:55many functions, particularly those of
16:57the autonomic nervous system. And so we
17:01have that their origin is given by
17:03tyrosine. Tyrosine is an amino acid
17:06that we have said is within the three
17:08essential ones. It means that it is an
17:11amino acid that the body does not form.
17:15Tyrosine must enter through
17:17phenylalanine. Phenylalanine is
17:20converted into tyrosine and it is the
17:22tyrosine that will act. Phenylalanine,
17:25one must remember, is an essential type
17:28of amino acid that needs to be
17:30incorporated into the diet normally. It
17:34will also form other compounds, but
17:36those that do not interest us much,
17:39such as morphine, codeine, papaverine,
17:41mescaline, etc., which are opioid
17:44derivatives, particularly from opium,
17:46that are immersed or have tyrosine in
17:49their composition. Well, arginine will
17:53participate in the synthesis of
17:56creatinine and creatinine interests us
17:59a lot. Creatinine has two sites where
18:02it is formed, as I had told you, or
18:04three sites where it is formed: the
18:06kidney, the liver, and the muscle. And
18:09the creatinine that enters the blood is
18:12the muscle creatinine. But for it to
18:15reach the blood, it has to go through
18:17several processes. In the kidney,
18:20creatinine is formed starting from
18:22arginine. In the kidney, arginine
18:26combines with glycine. These are two
18:29amino acids that will form a compound
18:31called guanidinoacetic acid. And in
18:34that process, ornithine is also
18:36generated as a waste product. So,
18:39arginine plus glycine forms
18:41guanidinoacetate or guanidinoacetic
18:44acid. And this acid, this compound,
18:48will travel to the liver, and in the
18:50liver, it will meet another amino acid.
18:54So, we now have three amino acids
18:56participating: arginine, glycine, and
18:58methionine. We must remember that 90%of
19:02the time, methionine is adenylated and
19:04is called S-adenosylmethionine. So,
19:08S-adenosylmethionine donates the methyl
19:10group and exits as homocysteine. Do not
19:14forget that homocysteine will later
19:16serve as a marker, and the origin of
19:19homocysteine is particularly in
19:21methionine. So, the guanidinoacetic
19:24acid in the liver asks methionine to
19:26donate a methyl group. Methionine
19:30leaves as homocysteine, and creatine is
19:32formed, not creatinine, creatine.
19:36Creatine will be phosphorylated and
19:40will generate, will form, a compound
19:44called creatine phosphate. Creatine
19:48phosphate is formed thanks to the
19:50enzyme creatine phosphokinase. This
19:53creatine phosphate is rich in
19:55high-energy phosphates and is
19:58considered the reserve of high-energy
20:01phosphates in cells for when ADP needs
20:05to be reconverted into ATP. Do not
20:09forget that the ATP-ADP cycle exists,
20:12and the high-energy phosphates return
20:15to ADP to form ATP. A source of
20:19high-energy phosphates is therefore
20:22constituted by creatine phosphates,
20:24which are found in many cells, not just
20:27muscle cells. Now, returning to the
20:30subject, creatinine begins its
20:32synthesis with arginine and glycine in
20:35the kidney. Then in the liver, it joins
20:38with methionine, forming creatine.
20:41Creatine is phosphorylated and stored
20:43as creatine phosphate deposits. And
20:47once the body needs phosphates, it
20:49immediately releases the phosphates,
20:51and creatine phosphate turns into
20:52creatinine. And there we have the
20:57chemical compound creatinine, which is
20:59a cyclic compound, if you notice, that
21:01enters the blood, giving us blood
21:03creatinine levels. That creatinine in
21:08the blood is called creatinemia, and
21:10creatinemia must disappear very quickly
21:13via the kidneys because it lasts a very
21:15short time in circulation. It is then
21:19immediately filtered by the glomerulus
21:21and removed into the urine. The faster
21:25creatinine is cleared from the blood,
21:28the better renal function is. The less
21:33creatinine there is in the blood, the
21:35better renal function is. So,
21:38creatinine today is established as one
21:41of the most important tests to
21:43determine whether a person is entering
21:45renal failure or not. The normal
21:49creatinine value is 1.0, but some
21:51laboratories may consider up to 1.3.
21:56You must always look at the
21:58laboratory's reference, the method they
22:00use, and the normal range value they
22:02are using. So, the creatinine that has
22:06been formed in the muscle leaves the
22:08muscle and immediately goes into the
22:10blood, is filtered by the kidney, and
22:12ends up in the urine. We can determine
22:16creatinine in plasma or we can
22:18determine creatinine in urine if we are
22:20performing kidney function studies.
22:26Nitric oxide is another important
22:29compound. Nitric oxide is a gas, and
22:33nitric oxide is also formed from
22:35arginine. So, look at the very
22:38important role of arginine, not just in
22:41forming creatine or creatinine, but
22:44also in forming nitric oxide. For
22:48nitric oxide to be formed, there are
22:50many, many processes and there are
22:53activators of an enzyme called nitric
22:55oxide synthase, abbreviated as NOS.
23:01Nitric oxide synthase exists in an
23:03inactive form, and when it is
23:04phosphorylated, it turns into an active
23:07form. And there are different subtypes
23:11of nitric oxide synthase, because in
23:14different tissues there is neuronal
23:16nitric oxide synthase, endothelial
23:18nitric oxide synthase, and nitric oxide
23:21synthase from other tissues. So we have
23:24several nitric oxide synthases there
23:26that will participate, and for that,
23:28they have to be active. Nitric oxide
23:32synthase is the enzyme that converts
23:34arginine into nitric oxide, abbreviated
23:37as NO, and as a remnant, it forms
23:39citrulline. Very similar to what the
23:44formation of urea was. Remember that in
23:47the urea cycle, citrulline is also
23:49generated, as well as ornithine. Well,
23:53then we have arginine, thanks to active
23:56nitric oxide synthase, forming nitric
23:58oxide. This nitric oxide from the
24:03endothelial cells migrates, escaping as
24:05a gas into the smooth muscle that is in
24:08the vessels, the smooth muscle of the
24:11vessels. And in the smooth muscles of
24:14the vessels, it activates an enzyme
24:17called guanylate cyclase. We know
24:19guanylate cyclase perfectly well
24:22because, along with adenylate cyclase,
24:24they generate second messengers. In
24:27this case, guanylate cyclase is also
24:31activated and uses GTP as a substrate
24:34to form cyclic GMP. Cyclic GMP acts as
24:39a relaxant in the vascular smooth
24:42muscle. It is a relaxant of vascular
24:45smooth muscle. Therefore, nitric oxide
24:49produces a relaxation of the smooth
24:51muscle that leads to vasodilation; the
24:54muscle relaxes, allowing more blood
24:56flow, it relaxes further, vasodilates
24:59more, and is transporting more blood.
25:03Therefore, nitric oxide is an
25:05extraordinary vasodilator. It acts as a
25:08gas formed in neighboring cells, not
25:11directly in smooth muscle cells, but it
25:13crosses over and activates guanylate
25:16cyclase, which will have the effect of
25:19increasing the proportion of cyclic GMP
25:22that will act as a smooth muscle
25:24relaxing compound. Now, nitric oxide is
25:28activated by some compounds and not by
25:31others. There are nitric oxides that
25:35are activated by acetylcholine,
25:37bradykinin, substance P, and
25:38particularly calcium. But there are
25:42other nitric oxide synthase enzymes
25:44that are not activated directly by
25:46these compounds. Therefore, not all of
25:49them depend on bradykinin,
25:51acetylcholine, and calcium to be
25:53activated. They can be activated by
25:56other mechanisms, particularly stress,
25:59not necessarily biochemical substances
26:01that activate nitric oxide synthase
26:03that was inactive and turn it into
26:06active nitric oxide synthase. But what
26:10has been observed most, particularly
26:12attached to endothelial cells, is that
26:15calcium is the most important activator
26:18of nitric oxide synthase so that it can
26:20relax vascular smooth muscle. Nitric
26:25oxide is very important because, I
26:28repeat, its extreme ability to dilate
26:32vessels allows blood to enter many
26:35sites. Nitric oxide synthase is used
26:40today to produce nitric oxide in some
26:43pathologies, particularly in pulmonary
26:45hypertension. It is used in newborns
26:49and is utilized as chemical products.
26:55This is the case of sildenafil, which
26:57is also used for erectile dysfunction
27:00and serves to increase circulation
27:03capacity in the event of pulmonary
27:05hypertension or pulmonary atresia; this
27:08medication is used. Sildenafil is based
27:13on producing nitric oxide and
27:15activating cyclic GMP. Cyclic GMP, I
27:19repeat, produces relaxation. The
27:22relaxation of the vascular tone and
27:24muscle allows for greater blood intake,
27:27and in the case of erectile dysfunction
27:30, the intake of more blood ensures
27:32perhaps better sexual function. Well,
27:37ornithine; ornithine was a byproduct
27:40that was being formed by arginine, and
27:43ornithine forms polyamines. In the past
27:48, the role played by ornithine and the
27:50polyamines derived from ornithine was
27:53not known. Today, it is known that
27:56these compounds act as growth factors
27:59and stabilize DNA, therefore, they are
28:01not negligible. Ornithine will form
28:05putrescine, putrescine will form
28:07spermidine, spermidine will form
28:09spermine, and so on and so forth. And
28:13their origins are in the sites where
28:15their greatest activity was found. But
28:19I repeat, ornithine derived from urea
28:22synthesis and as a byproduct of
28:25arginine serves to form polyamines that
28:28act as growth factors. And all growth
28:32factors are those molecules that
28:34promote cell division or mitosis. And
28:37there we have putrescine, spermine, and
28:39spermidine. Well, glutamic acid is
28:42another extraordinarily important amino
28:46acid, and it is important because it
28:48acts as a neurotransmitter; excess
28:51glutamic acid can be deadly. Great
28:55amounts of glutamic acid should not be
28:58produced because its excitatory action
29:01can lead to seizures and can even be, I
29:04repeat, lethal. Glutamic acid,
29:08glutamate, is an acidic amino acid.
29:12This glutamate is going to be formed
29:15starting from alpha-ketoglutarate. And
29:20alpha-ketoglutarate is an intermediate
29:22of the Krebs cycle. So it will form
29:25glutamic acid. Glutamic acid will also
29:28form glutathione. Remember that
29:31glutathione is the tripeptide we
29:32mentioned, with antioxidant action and
29:35the ability to prevent erythrocyte
29:37hemolysis. It will also form glutamine.
29:41Glutamine is an amino acid that
29:43requires glutamate as a source of
29:45nitrogen to form its structure. And
29:48perhaps one of the most important
29:50things about glutamate is that it will
29:52generate an inhibitory neurotransmitter
29:54. We have two neurotransmitters. So,
29:57glutamate or glutamic acid as an
29:59excitatory one, and GABA as an
30:01inhibitory one. In cells where
30:05glutamate is formed, GABA is also
30:07formed, so they go hand in hand. And
30:10these cells, particularly, are cells of
30:13the basal nuclei of the brain where
30:15these compounds are formed. They are
30:18also formed in other cells, there is no
30:20doubt, but especially at the brain
30:21level. The cells that form glutamate
30:25are called glutamatergic. And the cells
30:28that are involved in the formation of
30:30GABA, which are the same or very close
30:32neighbors, are called GABAergic. So, if
30:36we look at a glutamatergic cell, there
30:39is a presynaptic terminal, and the
30:41Krebs cycle is there in the
30:43mitochondria forming
30:44alpha-ketoglutarate.
30:47Alpha-ketoglutarate forms glutamate.
30:51Glutamate can also come from glutamine,
30:53thanks to glutaminase, which removes a
30:56nitrogenous group. Glutamine has two
30:58nitrogenous groups, and through
31:00glutaminase, an amino or nitrogenous
31:03group is lost, and it turns into
31:05glutamate. Be that as it may,
31:07alpha-ketoglutarate or glutamine form
31:09glutamate. Glutamate is found in these
31:14glutamatergic cells and is immediately
31:17stored in small vesicles; glutamate
31:20needs to exit the cell and usually does
31:24so through a calcium-induced exocytosis
31:27mechanism, and when glutamate enters
31:30the synaptic cleft, it goes to find its
31:34receptors. Glutamate receptors are
31:38different receptors, each one of them.
31:42Some glutamate receptors are associated
31:45with G-proteins, meaning they are
31:48G-protein-coupled, and others are
31:50coupled or are ion channels. Therefore,
31:55glutamate receptors, which are AMPA,
31:58NMDA, and others, such as kainate and
32:01quisqualate, will act as modulators,
32:04whether for ions or G-proteins. The
32:09interesting thing about glutamate is
32:11that a large proportion of it,
32:14approximately 75-80%, returns to the
32:17cell of origin, and this is called
32:19reuptake. Reuptake, just like with
32:24serotonin and noradrenaline, is a
32:26normal physiological process of the
32:28molecule re-entering the cell that gave
32:30rise to it. In the case of serotonin,
32:35if you recall, serotonin is also taken
32:37back up and returns to its origin. And
32:40what is done for people suffering from
32:43depression is to prevent the reuptake
32:46of serotonin. I am referring to
32:50serotonin, not glutamate, and that
32:53avoidance or blocking of reuptake
32:56causes serotonin to accumulate in the
32:59synaptic cleft and seek its 5-HT1, HT2,
33:03HT3, etc., receptors, and modulate mood
33:06, libido, wakefulness, and so on;
33:09because serotonin is related to many
33:12functions, particularly mood. And
33:17selective serotonin reuptake inhibitors
33:20are used as antidepressant medications.
33:24Well, returning to glutamate, glutamate
33:27then experiences the same thing: it
33:29reaches the postsynaptic cells, seeks
33:32its receptors, and once it acts with
33:34the receptor, it functions as a ligand
33:36for that receptor. It returns to the
33:40cell of origin and glutamate circulates
33:43again, is converted into glutamine by
33:45glutamine synthetase, the glutamine
33:47enters, and through glutaminase, it is
33:49converted back into glutamate; and it
33:51is an endless cycle. Glutamate is an
33:55excitatory neurotransmitter that must
33:57always be present in basal cells. An
34:01excess of glutamate, as I had told you,
34:04due to its action on receptors and the
34:06ionic movement it produces, could at
34:09some point damage the cell, cause cell
34:11death, and be lethal to the human
34:14person. Well, here we have glutathione,
34:19derived from glutamate. We had said
34:22that glutamate is a neurotransmitter,
34:25an acidic amino acid that joins with
34:27cysteine to form the compound
34:29glutamylcysteine. This joins with
34:32glycine and forms glutathione. I never
34:36tire of saying that glutathione is one
34:39of the most important compounds and is
34:41a lifesaver in the event of liver
34:43failure. Glutathione should be used
34:47without any fear; it is a source of
34:50cysteines, and glutathione, together
34:52with N-acetylcysteine and sulfates,
34:54along with glutathione peroxidase,
34:57frees us from free radicals called
34:59hydrogen peroxides that cause a lot of
35:01damage to cellular structures. Well,
35:06GABA was formed from glutamate. Here we
35:12have glutamate, which forms GABA, and
35:15GABA is formed thanks to a single
35:17enzyme called glutamic acid
35:19decarboxylase. Notice that there are
35:23many decarboxylases, as a single enzyme
35:26, to form biogenic amines. And that
35:29decarboxylation, or loss of carbons,
35:31generates important compounds. In this
35:35case, glutamate, through a
35:36decarboxylase named glutamic acid
35:39decarboxylase, forms GABA. And GABA has
35:42its name, which is gamma-aminobutyric
35:45acid. GABA is a compound that will be
35:49formed, I repeat, together with
35:50glutamate; glutaminergic cells and the
35:53cells that will experience an
35:55accumulation of GABA will be called
35:57GABAergic cells. This GABA will
36:02accumulate in vesicles, and those
36:05vesicles will have a large amount of
36:08GABA inside until the moment when
36:11calcium enters, the membrane polarity
36:13is altered, and the moment the membrane
36:17polarity is altered, GABA begins to
36:19exit into the synaptic cleft, and GABA,
36:22upon leaving its GABAergic cells, goes
36:25into the synaptic cleft. And it will
36:30search for its receptors. The receptors
36:33for GABA are inhibitory receptors and
36:36excitatory receptors. There are two
36:39types of receptors that GABA has. The
36:43receptor that is most used, and which
36:45GABA uses most as a neurotransmitter,
36:48is the type A receptor, GABA A. And the
36:51GABA A receptor modulates the entry of
36:53chloride into the cells. So, the
36:58activation of the GABA receptor by GABA
37:02causes this compound to start
37:05introducing chloride into the cell,
37:08depolarizing the membrane and ending
37:12the excitatory nerve impulse that was
37:15occurring. GABA is a compound, an
37:19inhibitory neurotransmitter that
37:21decreases excitation through the excess
37:23entry of chloride through the GABA
37:25receptor. GABA and its receptor have
37:29several subunits. It is a compound of
37:32four or five subunits that forms a
37:35channel for chlorine, and the chlorine
37:37begins to enter. Chloride and sodium
37:41also enter the cells and will produce
37:44both an inhibitory and an excitatory
37:47action. If exclusively chloride enters,
37:51it is an absolutely inhibitory reaction
37:54, and if sodium enters, it will be an
37:57excitatory reaction. Be that as it may,
38:0280 to 90%of GABA receptors are GABA A.
38:04And the GABA A is therefore related to
38:07the reduction of the nerve impulse and
38:10the termination of the excitatory
38:12process. Albinism, as we have said, is
38:18due to a lack of an enzyme, and
38:20albinism is a set of inherited
38:23congenital conditions that affect
38:26humans and are characterized by a
38:28decrease in the pigment called melanin.
38:33in the skin, eyes, and hair. If you
38:37look here at the photograph, we have an
38:40African tribe or ethnic group, and the
38:43last children have albinism. They all
38:47have Negroid characteristics, with very
38:50dark skin, but the last children have
38:52very white skin, and their hair is even
38:55almost transparent. The same thing here
39:00: the parents are of Negroid origin and
39:02the children, despite their Negroid
39:05features, are white in color. So skin
39:09color doesn't mean anything. We humans
39:12are absolutely equal, and more melanin
39:14or less melanin is of no greater
39:16importance. Albinism presents with
39:19various genetic defects in the body,
39:22and it is unable to produce melanin. it
39:25does not produce melanin, which is the
39:27substance that gives rise to the color
39:28of the irises, the skin, the hair,
39:30etcetera. Albinism is hereditary, and
39:34it is seen that there is an alteration
39:36in chromosome 11q, the short arm of
39:39chromosome 11, and it is transmitted in
39:41an autosomal recessive manner. There
39:45are several types of albinism, and many
39:47people have dedicated themselves to
39:49studying albinism, type one or type two
39:50albinism. In type one albinism, the
39:55production of the melanin pigment is
39:57affected, and in type two, there is an
40:00effect or a defect in the P gene, which
40:03is the specific gene that is altered so
40:05that no melanin is produced at all.
40:10Both cases of albinism are similar;
40:12there is no melanin pigment, but as I
40:15said, it is characterized by type one
40:17or type two, where there is a defect in
40:20the P gene, which is apparently the
40:23gene responsible for the greater
40:25production of this pigment on
40:27chromosome 11. In non-albino
40:30individuals, melanocytes transform the
40:33amino acid tyrosine into the substance
40:35known as melanin. If we consider that
40:39melanin is a derivative of tyrosine, it
40:41could be considered a biogenic amine;
40:44it is also a substance that provides
40:46color, but it has no function other
40:49than to produce a pigment; it does not
40:51have other types of implicit activities
40:54. Melanin is synthesized after a series
40:58of reactions driven by the enzyme
41:00tyrosinase. If you notice, tyrosinase
41:04sounds very similar to the term
41:07tyrosine kinase, and tyrosine kinase is
41:10an enzyme found in all signaling
41:13processes of type three receptors. When
41:18the receptor has dimerized and been
41:20endocytosed, the tyrosine kinase is
41:22activated, which phosphorylates the
41:23tyrosine. But in this case, the enzyme
41:28is simply called tyrosinase, and
41:30tyrosinase deficiency is what causes
41:33albinism. On the other hand, the other,
41:37tyrosine kinase, alters the
41:38intracellular signal or the signals
41:40implied with the type three receptor.
41:45Noradrenaline and adrenaline are
41:47compounds that are formed from tyrosine
41:50. Tyrosine is hydroxylated,
41:53incorporates an OH group, and becomes
41:56dopa. Dopa, its name stands for
42:00dihydroxyphenylalanine. That is its
42:03name, dihydroxy because it has two
42:05hydroxyl groups on the phenylalanine.
42:07Tyrosine comes from phenylalanine.
42:10Tyrosine has been formed thanks to the
42:12hydroxylation of phenylalanine, which
42:14has been incorporated at this site, and
42:16the tyrosine in turn is hydroxylated
42:18again and becomes dopa. Dopa is
42:21decarboxylated thanks to the enzyme
42:24dopa decarboxylase, loses this COOH
42:26group, and becomes dopamine. There is
42:30now a free nitrogen group down there,
42:32and that is dopamine. Dopamine will be
42:36converted into another compound which
42:38will be called noradrenaline, and
42:40noradrenaline will be converted into
42:42adrenaline. Noradrenaline is the
42:46precursor compound for adrenaline, and
42:48here the introduction of a methyl group
42:51will occur. Thanks to methyltransferase
42:55, a methyl group is introduced, and
42:57noradrenaline is formed. So, we have
43:00that the synthesis of noradrenaline and
43:02adrenaline occurs in a sequence.
43:05Tyrosine, dopa, dopamine, noradrenaline
43:07, and adrenaline. Well, here we have
43:11the same thing. We see tyrosine.
43:13Tyrosine, thanks to tyrosine
43:15hydroxylase, becomes dopa. Dopa,
43:17through dopa decarboxylase, becomes
43:20dopamine. Dopamine, through dopamine
43:23beta-hydroxylase, becomes noradrenaline
43:26. Do not forget that noradrenaline in
43:29Anglo countries, in the United States
43:31and England, is called norepinephrine.
43:34And noradrenaline becomes adrenaline or
43:37epinephrine, also called that by the
43:39Americans. And here, thanks to a
43:41phenylethanolamine N-methyltransferase.
43:44What you have to remember from this are
43:47the enzymes: tyrosine hydroxylase, dopa
43:49decarboxylase, dopamine
43:51beta-hydroxylase, and the
43:52methyltransferase that will form the
43:54catecholamines in that sequence. Anyone
43:58who asks how catecholamines are
44:00synthesized must state the sequence.
44:02Tyrosine, dopa, dopamine, noradrenaline
44:05, and adrenaline. Here we have tyrosine
44:08. It has entered, has formed dopa, and
44:10the dopa has formed dopamine. Dopamine
44:14is stored in vesicles along with ATP,
44:16it is always mixed with ATP, and the
44:19moment dopamine is released,
44:21noradrenaline is also released,
44:24particularly norepinephrine, which
44:26seeks out receptors in the synaptic
44:29cleft. Its receptors are the alpha and
44:33beta adrenergic receptors, and the
44:35enzyme that degrades it is COMT.
44:38Catechol-O-methyltransferase and MAO
44:40are the two enzymes that cause the
44:43catabolism of both noradrenaline and
44:45adrenaline at the same time. Alright.
44:50We'll stop here, guys. We'll see the
44:54continuation in the next class. Notice
44:56how interesting the topic is, and we'll
44:59see you on Thursday. Have a good
45:02morning. See you later. Goodbye.
45:06See you later, doctor.

About this transcript

This page contains the full transcript of BIOQUÍMICA 3ER PARCIAL Aminoacidos 26 08 25 by Teóricas de 3er año , generated from the public captions YouTube serves with the video. The transcript has 5,292 words across 897 segments, with the original timestamps preserved so you can click any line to jump to that moment in the embedded player.

What you can do with it

Use the transcript to take notes, quote the speaker, build a study guide, generate a summary with ChatGPT or Claude via the YouTube Summary tool, or export it as a timed subtitle file with YouTube to SRT. You can also re-open it in the transcriber to choose a caption track available on the video.

Free YouTube transcript tool

YouTube2Text is a free YouTube transcript generator — no signup, no daily limit. Paste any YouTube link and get the full transcript instantly, with timestamps, click-to-jump, caption language selection, AI prompts for ChatGPT, Claude, and Gemini, and exports to TXT, SRT, VTT, or Markdown.