Prática de Shadowing: Pyruvate Pathways & Metabolism - Aprenda a falar inglês com vídeo
Escolha um modo de prática
Cada modo abre uma sala de prática em tela cheia.
177 frases
Se as frases estiverem muito curtas ou longas, clique em Edit para ajustá-las.
1
Welcome back to Dirty Biochemistry.
2
In this lesson, we're going to discuss the pyruvate molecule
3
and how it is the most important molecule in determining which end product and which reaction pathway we ultimately choose to take.
4
This lesson is on pyruvate metabolism.
5
As a brief refresher, in the last lesson we discussed glycolysis and gluconeogenesis.
6
When you start with glucose and ultimately form pyruvate downstream, that is glycolysis, shown here in red.
7
If instead you move in the reverse direction, starting with pyruvate and going up to glucose, that is gluconeogenesis, shown here in blue.
8
Now that we have that brief refresher in mind, we need to talk about what we can actually do with pyruvate.
9
Now, I want you to think about pyruvate as the jack of all trades.
10
It is one of, if not the most important molecules in any of these biochemical pathways,
11
because pyruvate can at any point in time change itself
12
or transform itself through a chemical reaction into one of four different products.
13
So in all of these next examples, where we're going to go through four different biochemical pathways,
14
we're going to start with the reactant of pyruvate and ultimately be able to form four different end products.
15
The first pathway that pyruvic can take is to turn itself into lactic acid, aka lactate.
16
When it does this, we're talking about the pathway referred to as anaerobic glycolysis.
17
Now the word anaerobic means in the absence of oxygen.
18
Anaerobic.
19
There is no oxygen.
20
This is glycolysis occurring without the presence of oxygen.
21
Now normally, oxygen is hugely important in the ability to conduct glycolysis.
22
Recall that glycolysis and all metabolic pathways have one goal in mind,
23
and that is to work in tandem to form cofactors and reactants
24
that can be used with one another to ultimately send everything
25
to the electron transport chain to generate a massive amount of ATP.
26
Now I want to take a step back and think about the big picture here.
27
We have several different pathways and you need to know several different pathways, which will all be covered in this lecture series.
28
There's glycolysis, gluconeogenesis, the Krebs cycle, a .k .a the TCA cycle.
29
There is different protein formation and fatty acid synthesis.
30
But I want you to relax for a second and keep the big picture in mind.
31
All of these different pathways are working in tandem to form molecules
32
that will ultimately all be shunted into the electron transport chain where you generate the most massive amount of ATP.
33
That is the job of biochemical reactions occurring in the body.
34
So if we keep that in mind and remember
35
that oxygen is the ultimate or final electron acceptor in the electron transport chain,
36
it should come as no surprise to you that in the absence of oxygen,
37
which is to say that the electron transport chain will simply not work, there's no point in going through regular glycolysis.
38
In this case, we're going to shunt pyruvate through anaerobic glycolysis because there's no point in doing regular glycolysis,
39
again, because without oxygen, you don't have the final electron acceptor in the electron transport chain, so it's just a wasted reaction.
40
Now, with that in mind, it should make a little bit of sense why instead of going from glucose to pyruvate
41
and then sending pyruvate to the TCA cycle, we're just going to convert pyruvate to lactic acid.
42
And that's done in the anaerobic glycolysis pathway, which is going to be the first pyruvate pathway that we talk about today.
43
So I know that that was a pretty extensive aside,
44
but I really want you to keep the big picture in mind because when you get lost in these details,
45
you lose focus of what the actual purpose of these reactions are in the body.
46
So the conversion of pyruvate to lactic acid is what's termed anaerobic glycolysis.
47
And the enzyme that does this reaction is called lactate dehydrogenase, or LDH for short.
48
Now, this enzyme is active in certain conditions, and I've already told you that this is anaerobic glycolysis.
49
So it should come as no surprise that the main condition in which LDH is active is in low oxygen states.
50
Now, clinically, low oxygen states occur in things like infection, hypoxia, ischemia, and heart failure.
51
So when you ultimately become an upper level student and you go into the hospital,
52
you will not be surprised to learn that in states such as these, we obtain lactate levels when we test people's blood,
53
because an elevated lactate is telling us that the patient does not have adequate oxygenation,
54
and it cues us that there may be some underlying infection or some underlying hypoxic or ischemic event going on.
55
Now, in certain tissues...
56
This is the pathway that pyruvate will primarily go through.
57
And those tissues are shown here.
58
The testes, the lens, white blood cells, the cornea, the medulla of the kidney, and red blood cells.
59
This is simply a laundry list that you need to memorize.
60
But I have a mnemonic to make it a lot easier for you.
61
So I want you to think lactate when you can't make respirations.
62
So when you can't make respirations, which is to say that you don't have access to oxygen,
63
you will undergo anaerobic glycolysis and shunt pyruvate into lactic acid.
64
So the mnemonic here is think lactate when you can't make respirations.
65
T for testes, L for lens, W for white blood cell, C for cornea, M for medulla of the kidney, and R for red blood cells.
66
If you remember this mnemonic, you can remember all of the tissues where anaerobic glycolysis has a propensity to occur.
67
Now, in closing really briefly, I want to mention that the cofactor in the reaction catalyzed by lactate dehydrogenase is vitamin B3.
68
And in all of these situations, if there is a cofactor that's worth remembering, I'll include it briefly on the slide.
69
But that is the first possible pathway for pyruvate.
70
The next possible pathway for pyruvate is actually being able to be turned into alanine.
71
This conversion is referred to as the alanine aminotransferase pathway.
72
And the enzyme that converts pyruvate to alanine is ALT.
73
The cofactor here is vitamin B6.
74
Now you may be asking yourself, why would we want to turn pyruvate into alanine?
75
And the reason is something called the Cahill cycle.
76
So pyruvate is not able to jump between muscle and liver.
77
It's simply unable to do it.
78
So in order to recycle carbons between the muscle and the liver,
79
we actually have to disguise pyruvate as alanine or glucose to be able to make this a possibility.
80
So let's take a second and show you exactly what the Cahill cycle is and why it's such an advanced
81
adaptation that is a really remarkable thing.
82
So here on the left, you see a liver and here on the right, you see a muscle.
83
Obviously, I'm simplifying these drawings to show you some biochemical pathways.
84
So starting with pyruvate, you can turn pyruvate into alanine using the ALT enzyme that I've shown you on the previous slide.
85
This conversion will also use up glutamate and spit off alpha -ketoglutarate.
86
You need to memorize these are cofactors.
87
So it's pyruvate plus glutamate goes to alanine plus alpha -ketoglutarate.
88
Since pyruvate cannot jump between muscle and liver, alanine can.
89
That is why we convert the pyruvate into alanine.
90
Once you have the alanine, the alanine can go from the muscle into the liver.
91
Sneaky little alanine.
92
Alanine, once it's in the liver, can be converted back into pyruvate using alpha -ketoglutarate and spitting off a glutamate.
93
So it's the same reaction in the muscle, just backwards.
94
Once we have the pyruvate, we need to get the pyruvate back over into the muscle so that we can keep the cycle going.
95
But I told you that pyruvate cannot jump from liver to muscle or from muscle to liver.
96
So how do we accomplish this?
97
Well, in the Cahill cycle, we actually hack the system and use gluconeogenesis, which you already learned about in the first lesson.
98
So we go back up from pyruvate to glucose.
99
And that's just gluconeogenesis, folks.
100
Once we have the glucose, the glucose can jump from the liver to the muscle.
101
And then once in the muscle, we use glycolysis to go down from glucose to pyruvate.
102
Talk about an amazing system.
103
Look how awesome that is.
104
The red arrows shown on this slide on the left in the liver going from pyruvate up to glucose,
105
that is just gluconeogenesis, which you've already learned about.
106
And then on the right in the muscle, the red arrow going down from glucose to pyruvate, that's just glycolysis.
107
And you already know that.
108
So it's really the glucose and the alanine that's able to move between liver
109
and muscle to bring pyruvate across from muscle to liver.
110
And the whole reason that we do this is because pyruvate is a carbon molecule,
111
and we need to move those carbon molecules around to make use of certain materials in the body.
112
So this is the reason that we turn pyruvate into alanine.
113
It's to make use of the Cahill cycle.
114
Now, the Cahill cycle itself refers to everything you see here with red arrows.
115
It's the constant conversion from pyruvate to alanine, from alanine back to pyruvate, from pyruvate to glucose, from glucose back to pyruvate.
116
That cycle continues indefinitely while we regenerate glutamate and alpha -ketoglutarate on the side and use them as cofactors.
117
This is the Cahill cycle.
118
Now that's the reason that we would convert pyruvate to alanine.
119
And to quickly summarize so that you don't get lost, from pyruvate to lactic acid is anaerobic glycolysis, which occurs in low oxygen states.
120
From pyruvate to alanine, that is to shunt around and cycle.
121
carbon molecules using ALT through the Cahill cycle.
122
The next option for pyruvate is to be converted into oxaloacetate.
123
And the enzyme that does this conversion is pyruvate carboxylase using a cofactor of biotin.
124
Now we're not going to talk about this pathway too much,
125
but the goal here is to use oxaloacetate as an available reactant for either gluconeogenesis and or the TCA cycle.
126
Oxaloacetate can contribute to gluconeogenesis, but also the TCA cycle.
127
Truth be told, this is really just a fail safe in case the body needs to generate an additional reactant to push
128
it in either direction of gluconeogenesis or the TCA cycle.
129
So pyruvate has a lot of jobs, and one of them is to use pyruvate carboxylase
130
and biotin as a cofactor to generate oxaloacetate to simulate gluconeogenesis or the TCA cycle in certain situations.
131
That's really all you need to know about that pathway from pyruvate.
132
Not too much to know, but just something to keep in mind.
133
The final and perhaps most important pathway for pyruvate is its ability to be converted into acetyl -CoA.
134
The reason that this is so important is because acetyl -CoA is the chief reactant of the TCA cycle.
135
So without the conversion of pyruvate to acetyl -CoA, we would never be able to complete TCA cycle.
136
Now the enzyme that converts pyruvate to acetyl -CoA is pyruvate dehydrogenase.
137
Not only should you memorize pyruvate dehydrogenase, but you also need to memorize the five cofactors, vitamin B1, vitamin B2, vitamin B3,
138
vitamin B5, and lipoic acid.
139
Please, please, please memorize this.
140
It is extremely high yield.
141
Now, I told you, acetyl -CoA is the chief reactant of the TCA cycle.
142
So if you never convert pyruvate into acetyl -CoA, then you can never provide the reactant for the TCA cycle to spin the TCA cycle
143
and generate the carbon dioxide necessary to carry out a series of reactions that in unison, across all reactions,
144
will ultimately make use of different products to go to the electron transport chain and generate massive amounts of ATP.
145
That's the big picture.
146
The last thing that I want to point out is
147
that you'll notice that in the reactions of going from pyruvate to oxaloacetate and from pyruvate to acetyl -CoA, these are irreversible reactions.
148
They are one -sided arrows.
149
But going from pyruvate to lactic acid or pyruvate to alanine are reversible reactions.
150
And what you need to know about the differences here are
151
that oxaloacetate and acetyl -CoA are formed from pyruvate in the mitochondria,
152
whereas pyruvate to alanine and pyruvate to lactic acid are formed in the cytosol.
153
Please memorize that because occasionally test writers have been known to ask you exactly where these reactions take place.
154
I want to pause for a second
155
and summarize the high yield points from this lesson
156
because there was a lot of information and I don't want you to get lost in the details.
157
Glycolysis, gluconeogenesis, different types of synthesis, whether it's fatty acids, ketones,
158
or proteins, all of the chemical reactions in the body work together to generate an interactive set of reactants,
159
products, and cofactors that can ultimately go to the electron transport chain and generate a massive amount of ATP for the body.
160
We'll talk about the electron transport chain in another video in this series, but you should know right now
161
that the job of the electron transport chain is like a gigantic machine
162
that generates an enormous amount of energy for the body.
163
So all of these reactions have to find some way to work together to form everything needed to make that a possibility.
164
In low oxygen states where electron transport chain can simply not happen, pyruvate will go to lactic acid in low oxygen states such as infection,
165
ischemia, hypoxia, and heart failure.
166
LDH catalyzes that reaction.
167
In other scenarios, pyruvate will turn into alanine through ALT.
168
And the reason
169
that we do this is to satisfy the Cahill cycle's ability
170
to recycle carbon molecules from the liver to the muscle and vice versa.
171
In some situations, pyruvate can be turned into oxaloacetate using pyruvate carboxylase.
172
Oxaloacetate can stimulate gluconeogenesis, and it also has a secondary stimulating effect on the TCA cycle.
173
And lastly, pyruvate can be turned into acetyl -CoA by pyruvate dehydrogenase with five important cofactors.
174
Acetyl -CoA is the chief reactant in the TCA cycle, and without the ability to convert pyruvate into acetyl -CoA, it could never happen.
175
Acetyl -CoA and oxaloacetate are formed in the mitochondria, whereas alanine and lactic acid are formed in the cytosol.
176
That's it for this video.
177
Rewatch it if you need to, but pyruvate metabolism is extremely important.
Baixar aplicativo
Tudo o que você precisa para falar fluentemente
Pronúncia com IANota em cada frase
Prática de IPADomine cada som
VocabulárioMonte seu banco de palavras
Jogo de vocabulárioAprenda brincando
Mesmo canal
FOR YOU
Vídeo recomendado
C11
79 frases
Anaerobic Fermentation of Coffee 🧬☕
Daily ConversationUniversity StudentsWorking Adults
C11
746 frases
Blindboy discovers the link between gut health and mental health
Daily ConversationUniversity StudentsWorking Adults
C11
530 frases
Antimycobacterials | Anti-TB Drugs
Daily ConversationUniversity Students
C11
32 frases
Structure and Function of a Prokaryotic Cell (Bacteria)
Daily ConversationUniversity Students
C11
60 frases
Faces of Chemistry: Organic solar cells (BASF) - Video 2 (14+)
Daily ConversationUniversity Students
C12
189 frases
Creatine: is there truth behind the hype?
Daily ConversationUniversity StudentsWorking Adults
C1117 frases
Anatomy & Physiology: The Ultimate Beginner's Guide | Dr. Bee's Tutorials
Daily ConversationUniversity Students
C11
48 frases
Pharmaceutical Industry Overview | Pharma and Biotech: Distinctions | Understanding Pharmaceuticals
Daily ConversationUniversity StudentsWorking Adults
C1132 frases
Petroleum - 06 - Drilling Fluid Laboratory
Daily ConversationUniversity Students
C11
339 frases
Introduction to HPLC - Lecture 1: HPLC Basics
Daily ConversationUniversity Students
C11
7 frases
Diodes Explained - The basics how diodes work working principle pn junction
Daily ConversationUniversity StudentsWorking Adults
Vocabulário e dicas de fala para esta lição
Esta aula de conversação usa o vídeo “Pyruvate Pathways & Metabolism”. As palavras que mais se repetem: pyruvate, cycle, alanine, glycolysis, pathway. Este vídeo tem 177 frases e 2436 palavras para praticar shadowing. A fala dura 15:09. O falante fala em ritmo natural, cerca de 161 palavras por minuto, próximo de uma conversa do dia a dia. Apenas 74% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
15 palavras do vídeo que vale a pena aprender, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| pathway substantivo | /ˈpæθˌweɪ/ | via |
| muscle substantivo | /ˈmʌs.əl/ | músculo |
| oxygen substantivo | /ˈɑksɪd͡ʒən/ | oxigênio, oxigénio |
| glucose substantivo | /ˈɡluː.kəʊz/ | glicose, glucose |
| acid substantivo | /ˈæsɪd/ | ácido |
| electron substantivo | /ɪˈlɛk.tɹɑn/ | elétron, eletrão |
| convert verbo | /kənˈvɝt/ | converter, transformar |
| generate verbo | /ˈd͡ʒɛn.ə.ɹeɪt/ | gerar |
| molecule substantivo | /ˈmɑ.lɪ.kjul/ | molécula |
| conversion substantivo | /kənˈvɝʒən/ | conversão |
| vitamin substantivo | /ˈvɪt.ə.mɪn/ | vitamina |
| enzyme substantivo | /ˈɛn.zaɪm/ | enzima |
| lesson substantivo | /ˈlɛs.ən/ | lição |
| occur verbo | /əˈkɜː/ | ocorrer, acontecer |
| alpha substantivo | /ˈæl.fə/ | alfa |
Phrasal verbs que você vai ouvir
| Palavra | Pronúncia | Significado |
|---|---|---|
| carry out verbo | /ˈkæ.ɹi aʊt/ | carregar |
| point out verbo | apontar |
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | be covered · be shunted · is called |
| Present perfect have/has + particípio passado — uma ação passada que ainda importa agora | I've already told · I've shown · you've already learned |
| Orações relativas who / which + oração — informação extra sobre uma pessoa ou coisa | pathways, which will · pathway, which is · respirations, which is |
Pronúncia para ficar de olho
O falante usa 21 contrações e formas reduzidas, como we're, don't, can't. Diga-as na forma curta, do jeito que você ouve.
- Os sons de “th”: pathway /ˈpæθˌweɪ/, synthesis /ˈsɪnθəsɪs/
- Os sons de “sh” e “zh”: conversion /kənˈvɝʒən/, infection /ɪnˈfɛkʃən/, tissue /ˈtɪʃ.(j)u/, occasionally /əˈkeɪʒənəli/, accomplish /əˈkɑm.plɪʃ/
- Palavras longas — acerte a sílaba tônica: metabolism /məˈtæb.əˌlɪz.əm/, primarily /ˈpɹaɪ.mə.ɹə.li/, occasionally /əˈkeɪʒənəli/, interactive /ˌɪn.tɚˈæk.tɪv/, adaptation /ˌæd.æpˈteɪ.ʃən/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: acid /ˈæsɪd/, convert /kənˈvɝt/, generate /ˈd͡ʒɛn.ə.ɹeɪt/, slide /ˈslaɪ̯d/, yield /jiːld/
- /l/ final — a língua toca o céu da boca, não vira “u”: muscle /ˈmʌs.əl/, molecule /ˈmɑ.lɪ.kjul/, recall /ɹɪˈkɔl/, acetyl /ˈæsətɪl/, biochemical /ˌbaɪəʊˈkɛmɪkəl/
- /h/ — um sopro suave, diferente do “r”: whereas /(h)wɛɹˈæz/, hugely /ˈhjuːd͡ʒli/, dehydrogenase /diːˌhaɪdˈɹɒdʒəneɪz/, hypoxia /haɪˈpɔk.si.ə/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Comece na velocidade 0,75×, faça shadowing frase por frase e volte à velocidade normal quando ficar fácil.
- Grave a sua voz e compare com o original, prestando atenção a palavras como pathway, muscle, oxygen.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.