Практика Shadowing: Pyruvate Pathways & Metabolism - Изучайте разговорный английский по видео

Выберите режим практики

Каждый режим открывает полноэкранную комнату практики.

177 предложений

Если предложения слишком короткие или длинные, нажмите Edit, чтобы их изменить.

Welcome back to Dirty Biochemistry.

In this lesson, we're going to discuss the pyruvate molecule

and how it is the most important molecule in determining which end product and which reaction pathway we ultimately choose to take.

This lesson is on pyruvate metabolism.

As a brief refresher, in the last lesson we discussed glycolysis and gluconeogenesis.

When you start with glucose and ultimately form pyruvate downstream, that is glycolysis, shown here in red.

If instead you move in the reverse direction, starting with pyruvate and going up to glucose, that is gluconeogenesis, shown here in blue.

Now that we have that brief refresher in mind, we need to talk about what we can actually do with pyruvate.

Now, I want you to think about pyruvate as the jack of all trades.

It is one of, if not the most important molecules in any of these biochemical pathways,

because pyruvate can at any point in time change itself

or transform itself through a chemical reaction into one of four different products.

So in all of these next examples, where we're going to go through four different biochemical pathways,

we're going to start with the reactant of pyruvate and ultimately be able to form four different end products.

The first pathway that pyruvic can take is to turn itself into lactic acid, aka lactate.

When it does this, we're talking about the pathway referred to as anaerobic glycolysis.

Now the word anaerobic means in the absence of oxygen.

Anaerobic.

There is no oxygen.

This is glycolysis occurring without the presence of oxygen.

Now normally, oxygen is hugely important in the ability to conduct glycolysis.

Recall that glycolysis and all metabolic pathways have one goal in mind,

and that is to work in tandem to form cofactors and reactants

that can be used with one another to ultimately send everything

to the electron transport chain to generate a massive amount of ATP.

Now I want to take a step back and think about the big picture here.

We have several different pathways and you need to know several different pathways, which will all be covered in this lecture series.

There's glycolysis, gluconeogenesis, the Krebs cycle, a .k .a the TCA cycle.

There is different protein formation and fatty acid synthesis.

But I want you to relax for a second and keep the big picture in mind.

All of these different pathways are working in tandem to form molecules

that will ultimately all be shunted into the electron transport chain where you generate the most massive amount of ATP.

That is the job of biochemical reactions occurring in the body.

So if we keep that in mind and remember

that oxygen is the ultimate or final electron acceptor in the electron transport chain,

it should come as no surprise to you that in the absence of oxygen,

which is to say that the electron transport chain will simply not work, there's no point in going through regular glycolysis.

In this case, we're going to shunt pyruvate through anaerobic glycolysis because there's no point in doing regular glycolysis,

again, because without oxygen, you don't have the final electron acceptor in the electron transport chain, so it's just a wasted reaction.

Now, with that in mind, it should make a little bit of sense why instead of going from glucose to pyruvate

and then sending pyruvate to the TCA cycle, we're just going to convert pyruvate to lactic acid.

And that's done in the anaerobic glycolysis pathway, which is going to be the first pyruvate pathway that we talk about today.

So I know that that was a pretty extensive aside,

but I really want you to keep the big picture in mind because when you get lost in these details,

you lose focus of what the actual purpose of these reactions are in the body.

So the conversion of pyruvate to lactic acid is what's termed anaerobic glycolysis.

And the enzyme that does this reaction is called lactate dehydrogenase, or LDH for short.

Now, this enzyme is active in certain conditions, and I've already told you that this is anaerobic glycolysis.

So it should come as no surprise that the main condition in which LDH is active is in low oxygen states.

Now, clinically, low oxygen states occur in things like infection, hypoxia, ischemia, and heart failure.

So when you ultimately become an upper level student and you go into the hospital,

you will not be surprised to learn that in states such as these, we obtain lactate levels when we test people's blood,

because an elevated lactate is telling us that the patient does not have adequate oxygenation,

and it cues us that there may be some underlying infection or some underlying hypoxic or ischemic event going on.

Now, in certain tissues...

This is the pathway that pyruvate will primarily go through.

And those tissues are shown here.

The testes, the lens, white blood cells, the cornea, the medulla of the kidney, and red blood cells.

This is simply a laundry list that you need to memorize.

But I have a mnemonic to make it a lot easier for you.

So I want you to think lactate when you can't make respirations.

So when you can't make respirations, which is to say that you don't have access to oxygen,

you will undergo anaerobic glycolysis and shunt pyruvate into lactic acid.

So the mnemonic here is think lactate when you can't make respirations.

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.

If you remember this mnemonic, you can remember all of the tissues where anaerobic glycolysis has a propensity to occur.

Now, in closing really briefly, I want to mention that the cofactor in the reaction catalyzed by lactate dehydrogenase is vitamin B3.

And in all of these situations, if there is a cofactor that's worth remembering, I'll include it briefly on the slide.

But that is the first possible pathway for pyruvate.

The next possible pathway for pyruvate is actually being able to be turned into alanine.

This conversion is referred to as the alanine aminotransferase pathway.

And the enzyme that converts pyruvate to alanine is ALT.

The cofactor here is vitamin B6.

Now you may be asking yourself, why would we want to turn pyruvate into alanine?

And the reason is something called the Cahill cycle.

So pyruvate is not able to jump between muscle and liver.

It's simply unable to do it.

So in order to recycle carbons between the muscle and the liver,

we actually have to disguise pyruvate as alanine or glucose to be able to make this a possibility.

So let's take a second and show you exactly what the Cahill cycle is and why it's such an advanced

adaptation that is a really remarkable thing.

So here on the left, you see a liver and here on the right, you see a muscle.

Obviously, I'm simplifying these drawings to show you some biochemical pathways.

So starting with pyruvate, you can turn pyruvate into alanine using the ALT enzyme that I've shown you on the previous slide.

This conversion will also use up glutamate and spit off alpha -ketoglutarate.

You need to memorize these are cofactors.

So it's pyruvate plus glutamate goes to alanine plus alpha -ketoglutarate.

Since pyruvate cannot jump between muscle and liver, alanine can.

That is why we convert the pyruvate into alanine.

Once you have the alanine, the alanine can go from the muscle into the liver.

Sneaky little alanine.

Alanine, once it's in the liver, can be converted back into pyruvate using alpha -ketoglutarate and spitting off a glutamate.

So it's the same reaction in the muscle, just backwards.

Once we have the pyruvate, we need to get the pyruvate back over into the muscle so that we can keep the cycle going.

But I told you that pyruvate cannot jump from liver to muscle or from muscle to liver.

So how do we accomplish this?

Well, in the Cahill cycle, we actually hack the system and use gluconeogenesis, which you already learned about in the first lesson.

So we go back up from pyruvate to glucose.

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.

Скачать приложение

Всё для свободной речи

ИИ-оценка произношенияОценка каждой фразы

Практика IPAОсвойте каждый звук

СловарьСоберите свой словарный запас

Игра со словамиУчитесь играя

Сканировать QR

Download on theApp Store Get it onGoogle Play

Тот же канал

FOR YOU

Лексика и советы по произношению к этому уроку

Этот урок разговорной практики построен на видео «Pyruvate Pathways & Metabolism». Чаще всего повторяются слова: pyruvate, cycle, alanine, glycolysis, pathway. В этом видео 177 предложений и 2436 слов для шедоуинга. Речь длится 15:09. Говорящий говорит в естественном темпе, около 161 слов в минуту, близком к повседневной речи. Только 74% слов входят в 3000 самых частых слов английского языка, поэтому лексика сложная.

Ключевая лексика этого видео

15 слов из видео, которые стоит выучить, с произношением и значением:

Слово	Произношение	Значение
muscle существительное	/ˈmʌs.əl/	мы́шца, му́скул
oxygen существительное	/ˈɑksɪd͡ʒən/	кислоро́д
glucose существительное	/ˈɡluː.kəʊz/	глюко́за
acid существительное	/ˈæsɪd/	кислота́, кисля́тина
electron существительное	/ɪˈlɛk.tɹɑn/	электро́н
convert глагол	/kənˈvɝt/	превраща́ть, преврати́ть
generate глагол	/ˈd͡ʒɛn.ə.ɹeɪt/	порожда́ть, производи́ть
molecule существительное	/ˈmɑ.lɪ.kjul/	моле́кула
conversion существительное	/kənˈvɝʒən/	превраще́ние, обраще́ние
vitamin существительное	/ˈvɪt.ə.mɪn/	витами́н
enzyme существительное	/ˈɛn.zaɪm/	ферме́нт, энзи́м
lesson существительное	/ˈlɛs.ən/	уро́к, ле́кция
occur глагол	/əˈkɜː/	происходи́ть, произойти́
alpha существительное	/ˈæl.fə/	а́льфа
arrow существительное	/ˈæɹəʊ/	стрела́

Фразовые глаголы, которые вы услышите

Слово	Произношение	Значение
carry out глагол	/ˈkæ.ɹi aʊt/	выноси́ть, вы́нести
point out глагол		ука́зывать, указа́ть
use up глагол		занима́ть, заня́ть

Грамматика в этом видео

Конструкции, которые говорящий использует чаще всего, с точными словами из видео:

Конструкция	В видео
Пассивный залог be + причастие прошедшего времени — важно, что происходит, а не кто это делает	be covered · be shunted · is called
Present Perfect have/has + причастие прошедшего времени — прошлое действие, важное сейчас	I've already told · I've shown · you've already learned
Придаточные определительные who / which + предложение — уточнение о человеке или предмете	pathways, which will · pathway, which is · respirations, which is

Произношение, на которое стоит обратить внимание

Говорящий использует 21 сокращённых и редуцированных форм, например we're, don't, can't. Произносите их коротко, так, как слышите.

Звуки «th»: pathway /ˈpæθˌweɪ/, synthesis /ˈsɪnθəsɪs/
Звуки «sh» и «zh»: conversion /kənˈvɝʒən/, infection /ɪnˈfɛkʃən/, tissue /ˈtɪʃ.(j)u/, occasionally /əˈkeɪʒənəli/, accomplish /əˈkɑm.plɪʃ/
Длинные слова — следите за ударением: metabolism /məˈtæb.əˌlɪz.əm/, primarily /ˈpɹaɪ.mə.ɹə.li/, occasionally /əˈkeɪʒənəli/, interactive /ˌɪn.tɚˈæk.tɪv/, adaptation /ˌæd.æpˈteɪ.ʃən/

Звуки, трудные для русскоязычных:

/w/ — губы округлены, это не /v/: pathway /ˈpæθˌweɪ/, whereas /(h)wɛɹˈæz/, adequate /ˈæd.ə.kwɪt/, backward /ˈbækwɚd/, rewatch /ɹiːˈwɒtʃ/
/h/ — лёгкий выдох, а не русское «х»: whereas /(h)wɛɹˈæz/, hugely /ˈhjuːd͡ʒli/, dehydrogenase /diːˌhaɪdˈɹɒdʒəneɪz/, hypoxia /haɪˈpɔk.si.ə/
Звонкие согласные в конце слова — не оглушайте их: glucose /ˈɡluː.kəʊz/, acid /ˈæsɪd/, slide /ˈslaɪ̯d/, whereas /(h)wɛɹˈæz/, lens /lɛnz/

Как заниматься с этим видео

Прослушайте всё видео один раз молча и выпишите незнакомые слова.
Начните со скорости 0,75×, повторяйте предложение за предложением и вернитесь к обычной скорости, когда станет легко.
Запишите себя и сравните с оригиналом, обращая внимание на такие слова, как muscle, oxygen, glucose.

Что такое техника Shadowing?

Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.

Техника шедоуинга: читать полное пошаговое руководство →

Практика Shadowing: Pyruvate Pathways & Metabolism - Изучайте разговорный английский по видео

Выберите режим практики

Скачать приложение

Тот же канал

Retinal Artery Occlusion vs. Retinal Vein Occlusion

Glycolysis

Embryology of the Nervous System

Lymphoma

Рекомендуемое видео

Anaerobic Fermentation of Coffee 🧬☕

Blindboy discovers the link between gut health and mental health

Antimycobacterials | Anti-TB Drugs

Structure and Function of a Prokaryotic Cell (Bacteria)

Faces of Chemistry: Organic solar cells (BASF) - Video 2 (14+)

Creatine: is there truth behind the hype?

Anatomy & Physiology: The Ultimate Beginner's Guide | Dr. Bee's Tutorials

Pharmaceutical Industry Overview | Pharma and Biotech: Distinctions | Understanding Pharmaceuticals

Petroleum - 06 - Drilling Fluid Laboratory

Introduction to HPLC - Lecture 1: HPLC Basics

Diodes Explained - The basics how diodes work working principle pn junction