ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: Glycolysis
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170 ประโยค
หากประโยคสั้นหรือยาวเกินไป กดที่ Edit เพื่อปรับแก้
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Welcome back to the high -yield biochemistry series.
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This is brought to you by Dirty Medicine.
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In today's video, we're going to continue our discussion about the biochemical pathways and talk about glycolysis.
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Glycolysis is typically the first biochemical pathway that you learn when you're learning about biochemistry, and it's because of that that it's extremely high -yield.
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It shows up on exams all of the time.
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Now, when you're learning about glycolysis, as you'll see me mention throughout this video, it's really important to remember the bigger picture.
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And when I say that, I'm referring to things like what is the function or the role of glycolysis?
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What are we taking as a reactant and turning into a product?
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And what are the regulatory mechanisms in terms of feedback?
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So what makes this go forward?
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What inhibits this?
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And what is the rate limiting enzyme?
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Just like all of the biochemistry videos that I've created, you need to know the rate -limiting enzyme and the regulatory mechanisms.
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So we're talking about things like inhibitors, etc. So let's start with a quick overview of glycolysis.
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Glycolysis is an irreversible biochemical reaction that occurs in the cytoplasm.
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The net equation for glycolysis is that you start with glucose, and the goal is to take that glucose and turn it into pyruvate,
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where it can downstream take multiple pathways through that pyruvate pathway
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and preferentially usually this goes into the citric acid cycle
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but here's the net equation you've you start with glucose
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and you add two phosphates two adps and two nads
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and what you get out of
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that is two 2 pyruvates plus 2 ATPs plus 2 NADH plus 2 hydrogens plus 2 waters.
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But if you wanted to just think very simply about what glycolysis is doing,
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it's taking glucose and breaking that glucose down into storable products that the body can use in other biochemical pathways.
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So now that we've understood the overview of glycolysis, let's just get into the meat and potatoes here.
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We're going to talk about the pathway.
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You need to understand the pathway, and I'm going to pay very special attention to the regulatory mechanisms of this pathway and the rate -limiting enzyme.
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So you start with glucose, right?
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Any person takes a bite of a cheeseburger, eats a french fry, drinks a milkshake, and they've got a bunch of carbohydrate in their body.
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And that carbohydrate is composed usually of glucose.
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And if it's not of glucose, then the other types of sugars will get turned into glucose so
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that glycolysis can utilize
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it the first step is glucose will get turned into glucose
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6 -phosphate glucose 6 -phosphate will get turned into fructose
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6 -phosphate fructose 6 -phosphate will get turned into fructose 1 -6 -bisphosphate
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and now you've got like multiple steps
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that are going to happen there's going to be four
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or five more reactions in this pathway and you'll end up with phosphoenolpyruvate which will get turned into pyruvate.
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And going from glucose down to pyruvate is the entire glycolysis pathway.
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So when you get to pyruvate you're basically finished with glycolysis.
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Now let's talk about the important enzymes that you need to know.
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So the first step that converts glucose to glucose 6 -phosphate, there's actually two different enzymes
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that can be used depending on the circumstances of the glucose concentration and where in the body we're talking about.
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So those two enzymes are glucokinase and hexokinase.
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So to be perfectly clear, either glucokinase or hexokinase can convert glucose to glucose 6 -phosphate.
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And what you'll need to know for test day that's really high yield is to understand under
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which circumstances both of these enzymes might be used.
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So for glucokinase, this enzyme has a low affinity and a high
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Km, Just remember the reciprocal relationship between affinity and Km.
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The higher the Km, the lower the enzyme has an affinity for its substrate.
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So glucokinase has a low affinity for glucose.
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It typically doesn't want to go and grab glucose.
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And the reason for this is because glucokinase acts as a glucose sensor.
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It's present in the liver and the pancreatic beta cells, and it's only used when glucose is at high concentrations.
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So basically what you should think of glucokinase as is an emergency enzyme that is acting as a glucose sensor.
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And it's really not grabbing glucose because instead of grabbing glucose and breaking it down through glycolysis,
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what it's doing is it's sensing glucose and it's going, okay, let's test how much glucose is over here.
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uh that's okay we're not going to jump in yet um hexokinase you go first
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so hexokinase on the other hand that is a high affinity enzyme
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which means it has a low km and
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because it has high affinity for its substrate hexokinase is the one that's constantly going to be latching onto glucose
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and converting it to glucose 6 -phosphate and sending it down the glycolysis pathway
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and the reason for that is because hexokinase is the enzyme that's used to operate the basal glucose metabolism.
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So constantly throughout your body in all of your tissues, you have this enzyme hexokinase that's just keeping a basal level of glucose metabolism present.
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It's trying to make sure that your glucose level is adequate throughout the body in all of the tissues.
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But if hexokinase becomes overwhelmed because suddenly there's a massive influx of glucose, that is when hexokinase turns to glucokinase and says,
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glucose, I know you usually have a low affinity, but I really need some help now because the glucose concentration is high.
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So if you think about it, that's the reason that glucokinase is only found in the liver and the pancreatic beta cells,
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because it does a very specific regulatory job where it's only acting when the blood glucose levels are super, super high.
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When that concentration reaches some critical point, that's when glucokinase in the liver and the pancreatic beta cells jumps in to save hexokinase.
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So the takeaway from this slide is that both glucokinase
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and hexokinase are enzymes that catalyze that conversion from glucose to glucose 6 -phosphate.
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The only difference is that hexokinase is kind of there all of the time, making a basal level of glucose, and glucokinase jumps in in emergencies.
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But understand the differences between those two enzymes that I've put in the gray boxes.
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They are extremely high yield and probably will show up on your test.
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So here's where we are.
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We've talked about the enzymes in the first step.
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The enzyme that converts fructose 6 -phosphate to fructose 1 ,6 -bisphosphate is the rate -limiting enzyme of glycolysis,
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and that's phosphofructokinase 1.
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Sometimes you'll hear this referred to as PFK1.
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So PFK1, or phosphofructokinase 1, is the rate -limiting enzyme, and it converts fructose 6 -phosphate to fructose 1 ,6 -bisphosphate.
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Now, I told you at the start of this video
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that the very important thing to keep in mind for USMLE and Comlex is the regulatory mechanisms.
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And what I mean when I say regulatory mechanisms are what inhibits this pathway and what promotes this pathway.
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And we're going to talk about that for the first time right here.
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And because phosphofructokinase 1 is the rate -limiting enzyme,
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it's really high yield to understand what inhibits phosphofructokinase 1 and what promotes phosphofructokinase 1.
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And that's what you see here.
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So ATP and citrate will inhibit the rate -limiting enzyme PFK1,
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but AMP will promote the rate -limiting enzyme of PFK1.
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And this should be somewhat intuitive to you.
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So think about what glycolysis is doing.
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The role of glycolysis is to take glucose, convert it to pyruvate and ATP,
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and then let that pyruvate enter one of many different pathways, but usually the citric acid cycle where you'll then create citrate.
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So if you think about that,
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the question becomes, what would this pathway want to do if it already had ATP and therefore didn't need to make it,
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or if it already had citrate and therefore didn't need to make pyruvate, which would then go to citrate.
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And that's why ATP and citrate inhibit PFK1, because if you have ATP and you already have citrate, then you don't need to do glycolysis.
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So the presence of those products will inhibit the rate -limiting enzyme, and therefore glycolysis won't occur.
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Now, likewise, think about AMP.
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If you have AMP, which is monophosphate, only one, you don't have ATP.
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And therefore, if you don't have ATP, you want to do glycolysis.
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So in the presence of AMP, which is to say in a situation where you don't have ATP,
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AMP will promote PFK1 and will therefore promote glycolysis.
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So anytime you're not really sure about how the regulatory mechanisms are working, think about this intuitively.
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Ask yourself on test say, well, would glycolysis happen if there was AMP?
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Would glycolysis happen if there was citrate?
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It should make sense to you if you understand what the big picture role of these pathways are.
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So that's what promotes and inhibits PFK1.
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Now I need to pause for a second and tell you about this little nuance of glycolysis.
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So fructose 6 -phosphate can go to fructose 1 ,6 -bisphosphate as you see on this slide.
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But additionally, there's sort of a side step that occurs, a pivot if you will.
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Fructose 6 -phosphate can also become fructose 2 ,6 -bisphosphate.
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And if fructose 6 -phosphate will become fructose 2 ,6 -bisphosphate,
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the enzyme that catalyzes this conversion is phosphofructokinase 2, PFK2.
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So very similarly named, of course, to the rate limiting enzyme that we just talked about, but instead of 1, it's 2.
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So when this happens, you create fructose 2 ,6 -bisphosphate.
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And interestingly, that fructose 2 ,6 -bisphosphate will promote PFK1.
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So the goal when the body does this is to make glycolysis happen faster.
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Now the question then becomes what is promoting or inhibiting phosphofructokinase 2 or PFK2?
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And that's really simple.
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So it's going to be inhibited by glucagon and it's going to be promoted by insulin.
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So think about it.
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If fructose 2 ,6 -bisphosphate makes glycolysis happen faster.
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And in glycolysis, you're breaking down glucose.
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It makes sense that insulin will promote PFK2 because in the presence of glucose,
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the body's going to secrete insulin and the body's telling anything that any cell that has a glycolysis pathway occurring, it's like, yo, take that glucose,
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break it down, please get this out of the system.
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And that's insulin's role.
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The opposite of that is glucagon.
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Glucagon's putting the brakes on this pathway and saying, yo, chill, we need to reverse this and make energy available because blood glucose is low.
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So think about it, guys.
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Insulin will promote PFK2 because it will make fructose 2 ,6 -bisphosphate, which feeds back to PFK1 and makes this happen faster.
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But in another situation, glucagon will inhibit PFK2 because PFK2 would normally make fructose 2 ,6 -bisphosphate,
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which would feed back to PFK1 and make this process happen faster.
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So again, understanding the big picture about what glycolysis is actually doing helps you understand the regulatory mechanisms
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that you need to memorize for your test.
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So the takeaway from this slide is that PFK2 inhibited by glucagon and promoted by insulin.
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The last enzyme that we need to talk about is the enzyme that converts phosphoenolpyruvate to pyruvate, the last step of glycolysis.
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That enzyme is pyruvate kinase.
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And just like PFK1, this is going to be inhibited by ATP and citrate for the same exact reasons.
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And those reasons are, again, glycolysis wants to create ATP.
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Glycolysis wants to make pyruvate, which can then become citrate in the TCA cycle.
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So therefore, if you already have ATP or you already have citrate, what's the point?
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You don't need to do glycolysis.
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So the presence of those products will inhibit the enzymes that usually make glycolysis work.
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So guys, that's it for glycolysis.
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And you're probably sitting there starting to have a panic attack thinking about, whoa, dirty.
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What about all the other enzymes?
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Don't worry about the other enzymes.
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This is what you need to know for USMLE and Comlex.
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You need to know the enzymes I put in these slides, the regulatory mechanisms that I put in these slides,
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and understand the difference between glucokinase and hexokinase that we discussed at the beginning of this video.
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All of the other intermediary steps, you don't need to know them.
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You really don't.
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They're not going to show up on your test unless you're taking a college level or intro to biochemistry course.
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You really don't need to know them.
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If you do want to know them for completeness sake, I would encourage you to go online, look at some diagrams, memorize some enzymes.
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But this is what you need to know to answer 99 % of the questions that will show up on USMLE,
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Comlex, your question banks, your practice tests, et cetera.
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So again, and I cannot stress this enough because it's the biggest theme for all of biochemistry.
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Know the rate limiting enzyme, know the regulatory mechanisms.
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And if you get stuck on test day about what's inhibiting or what's promoting, ask yourself, what's the goal of this pathway?
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And therefore, what do I think might happen?
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That's it.
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If you liked this video, drop me a like or a comment in the comment section.
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Please remember to check my Patreon page.
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You can click
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and support the channel love you good luck
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คำศัพท์และข้อสังเกตด้านการพูดสำหรับบทเรียนนี้
คำที่ถูกพูดซ้ำบ่อยที่สุด: glucose, glycolysis, enzyme, pathway, fructose วิดีโอนี้มี 170 ประโยค และ 2233 คำ สำหรับฝึกพูดตาม ช่วงที่มีเสียงพูดยาว 14:16 ผู้พูดพูดด้วยความเร็วเป็นธรรมชาติ ประมาณ 156 คำต่อนาที ใกล้เคียงกับบทสนทนาในชีวิตประจำวัน มีเพียง 76% ของคำที่อยู่ใน 3,000 คำที่ใช้บ่อยที่สุดในภาษาอังกฤษ คำศัพท์จึงค่อนข้างยาก
คำศัพท์สำคัญในวิดีโอนี้
คำที่ควรเรียนรู้ 15 คำจากวิดีโอ พร้อมคำอ่านและความหมาย:
| คำศัพท์ | คำอ่าน | ความหมาย |
|---|---|---|
| glucose คำนาม | /ˈɡluː.kəʊz/ | กลูโคส |
| enzyme คำนาม | /ˈɛn.zaɪm/ | เอนไซม์ |
| mechanism คำนาม | /ˈmɛk.ə.nɪ.zəm/ | กลไก, เครื่อง |
| slide คำนาม | /ˈslaɪ̯d/ | กระดานลื่น |
| insulin คำนาม | /ˈɪnsəlɪn/ | อินซูลิน |
| occur คำกริยา | /əˈkɜː/ | เกิด |
| beta คำนาม | /ˈbeɪtə/ | บีตา |
| acid คำนาม | /ˈæsɪd/ | กรด |
| tissue คำนาม | /ˈtɪʃ.(j)u/ | ทิชชู่ |
| equation คำนาม | /ɪˈkweɪ.ʒən/ | สมการ |
| circumstance คำนาม | /ˈsɝ.kəmˌstæns/ | กรณี, สถานการณ์ |
| encourage คำกริยา | /ɪnˈkʌɹ.ɪd͡ʒ/ | ให้กำลังใจ, ส่งเสริม |
| gray คำคุณศัพท์ | /ɡɹeɪ/ | เทา |
| bite คำกริยา | /baɪt/ | กัด |
| panic คำนาม | /ˈpænɪk/ | ความตื่นกลัว |
ประโยคที่ควรฝึกพูดซ้ำ
ประโยคสั้น ๆ ที่สมบูรณ์จากวิดีโอ ซึ่งนำไปใช้ในบทสนทนาประจำวันได้:
- What are we taking as a reactant and turning into a product?
- We're going to talk about the pathway.
- We've talked about the enzymes in the first step.
- You don't need to do glycolysis.
- You really don't need to know them.
ไวยากรณ์ในวิดีโอนี้
โครงสร้างที่ผู้พูดใช้บ่อยที่สุด พร้อมคำพูดจริงจากวิดีโอ:
| โครงสร้าง | ในวิดีโอ |
|---|---|
| Passive voice be + กริยาช่อง 3 — เน้นสิ่งที่เกิดขึ้น ไม่ใช่ผู้กระทำ | is brought · is composed · is only found |
| Present perfect have/has + กริยาช่อง 3 — เหตุการณ์ในอดีตที่ยังเกี่ยวข้องกับปัจจุบัน | I've created · we've understood · I've put |
| Relative clauses who / which + อนุประโยค — ข้อมูลเพิ่มเติมเกี่ยวกับคนหรือสิ่งของ | phosphoenolpyruvate which will · AMP, which is · pyruvate, which can |
การออกเสียงที่ควรระวัง
ผู้พูดใช้รูปย่อและรูปลดเสียง 41 ครั้ง เช่น don't, you're, we're ให้พูดแบบสั้นตามที่ได้ยิน
- เสียง “sh” และ “zh”: concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, tissue /ˈtɪʃ.(j)u/, conversion /kənˈvɝʒən/, equation /ɪˈkweɪ.ʒən/, donation /doʊˈneɪʃən/
- คำยาว — ลงเสียงหนักให้ถูกพยางค์: regulatory /ˈɹɛɡ.jʊ.lə.t(ɔː.)ɹi/, mechanism /ˈmɛk.ə.nɪ.zəm/, affinity /əˈfɪnɪti/, concentration /ˌkɑn.sənˈtɹeɪ.ʃən/, metabolism /məˈtæb.əˌlɪz.əm/
เสียงที่คนไทยมักออกเสียงยาก:
- เสียงท้ายคำ — ออกเสียงให้ครบ ไม่เปลี่ยนเป็นตัวสะกดแบบไทย: glucose /ˈɡluː.kəʊz/, circumstance /ˈsɝ.kəmˌstæns/, encourage /ɪnˈkʌɹ.ɪd͡ʒ/, reverse /ɹɪˈvɝs/, chill /tʃɪl/
- /v/ — ไม่ใช่ /w/ ให้ฟันบนแตะริมฝีปากล่าง: convert /kənˈvɝt/, conversion /kənˈvɝʒən/, overview /ˈoʊ.vɚˌvjuː/, reverse /ɹɪˈvɝs/, intuitive /ɪnˈtjuːɪtɪv/
- /z/ — เสียงก้อง ไม่ใช่ /s/: glucose /ˈɡluː.kəʊz/, enzyme /ˈɛn.zaɪm/, mechanism /ˈmɛk.ə.nɪ.zəm/, metabolism /məˈtæb.əˌlɪz.əm/, exam /ɪɡˈzæm/
วิธีฝึกกับวิดีโอนี้
- ฟังวิดีโอให้จบหนึ่งรอบโดยยังไม่ต้องพูด แล้วจดคำที่ยังไม่รู้จัก
- เริ่มที่ความเร็ว 0.75× พูดตามทีละประโยค แล้วกลับไปใช้ความเร็วปกติเมื่อเริ่มคล่อง
- อัดเสียงตัวเองแล้วเทียบกับต้นฉบับ โดยสังเกตคำอย่าง glucose, enzyme, mechanism เป็นพิเศษ
เทคนิค Shadowing คืออะไร?
Shadowing เป็นเทคนิคการเรียนรู้ภาษาที่ได้รับการรับรองทางวิทยาศาสตร์ พัฒนาขึ้นสำหรับการฝึกนักแปลมืออาชีพ วิธีการนี้เรียบง่ายแต่ทรงพลัง: คุณฟังเสียงภาษาอังกฤษจากเจ้าของภาษาและพูดตามทันที — เหมือนเงาที่ตามผู้พูดด้วยช่วงเวลาห่าง 1-2 วินาที การวิจัยแสดงว่าเทคนิคนี้ปรับปรุงความแม่นยำในการออกเสียง ทำนองเสียง จังหวะ การเชื่อมเสียง การฟังเข้าใจ และความคล่องแคล่วในการพูดได้อย่างมีนัยสำคัญ