Rate-Limiting Enzymes and Their Regulation | MCAT
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- Опубліковано 28 лип 2024
- TL;DR: The rate-limiting enzyme of any metabolic process is the enzyme that catalyzes the slowest, or rate-limiting, step of that metabolic process. Its regulation is specifically important because it determines not just the rate of that specific reaction, but the rate of the overall metabolic process.
Today’s MedCat video covers the different rate-determining (aka rate-limiting) enzymes of glycolysis, the Krebs cycle [aka Citric Acid Cycle (CAC) or Tricarboxylic Acid Cycle (TCA Cycle)], gluconeogenesis, glycogenesis, glycogenolysis, and the pentose-phosphate-pathway [aka hexose-monophosphate shunt (HMP shunt)]. All of these enzymes (listed below) are covered with their major substrates, coenzymes, and cofactors, as well as their relevant regulators.
Phosphofructokinase-1 (PFK-1)
Isocitrate dehydrogenase
Fructose-1,6-bisphosphatase
Glycogen synthase
Glycogen phosphorylase
Glucose 6-P dehydrogenase (G6PDH or G6P dehydrogenase)
Time Stamps:
Intro: (0:00)
What Is a Rate-Limiting Enzyme?: (0:08)
Rate-Determining Enzymes: (1:52)
Regulation of Rate-Determining Enzymes: (8:15)
Outro: (13:03)
Comprehensive Amino Acid Playlist: bit.ly/3sMGBUG
Check out Aratasaki, the beat maker behind my intro and outro: bit.ly/2Pma5v0
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All content and media on this channel is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice.
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#mcat #ratelimitingenzymes #enzymeregulation
Rate-Limiting Enzymes and Their Regulation | MCAT
Rate-Limiting Enzymes and Their Regulation | MCAT
Rate-Limiting Enzymes and Their Regulation | MCAT
This is super helpful! I was about to make my own list of Rate Limiting Steps for each Metabolic pathway before I saw this! These High Yield videos are the best.
Glad it was helpful!
Feel free to leave questions!
I’ve been binging your videos. You help me more than you can know.
Thank you so much! This is the motivation I need to film this next video.
@@medcatmcat I understand that its discouraging to put effort and not get a lot of views, but thats just the nature of making educational content on youtube nowadays. Ive sent this to my friends so my whole community will be benefitting from your work. The way i see it…youre a hidden gem for people who want to do good. Theres some merit in that too!
Great video. There was something that I was a little confused on. I thought cortisol had a similar effect on the body like a sympathetic response. Which increases blood glucose levels. So I figured that cortisol would down regulate glycogen synthase. I could be wrong, but those two things seem opposed. Cortisol and glycogenesis
Yeah, cortisol is a weird one! For the purpose of the MCAT, I think it would be quite unlikely they would ask you about cortisol's regulation of glycogen-it's much more likely that glucagon or insulin is tested. If they ask you about cortisol in relation to glucose, it will likely be more about it upregulating gluconeogenesis.
That being said, if you want some confusing reasoning, a few articles posit that we make more glycogen so that we can then rapidly mobilize that glycogen store if we need it later. Why our body does this, I'm not sure. Here's one of the best articles I could find: link.springer.com/chapter/10.1007/978-1-4939-2895-8_5 . It's also worth noting that the acute and long-term effects of cortisol are different.
You the man, man
:)
Why is glycogen synthase upregulated by cortisol? Cortisol typically released during stress, is one of the hormones/molecules that act to synthesize glucose from non carbohydrate sources. As such, wouldn't it inhibit an enzyme that acts to make the storage form, glycogen?
Great video this was helpful.
Thanks.
That's a great question! You're right: cortisol upregulates gluconeogenesis and lipolysis, both of which make sense for our acute stress response. For the MCAT, you really just need to know that it upregulates gluconeogenesis.
My admittedly limited understanding is that while gluconeogenesis is upregulated and raising blood glucose, it also might be nice to have a larger glycogen store available so that for another stress response we are able to break that glycogen down later. Remember that we have the help of catecholamines like epinephrine to induce glycogenolysis during the acute stress response, so you could consider that glycogen is built up by cortisol, and epinephrine helps break down that glycogen when it is needed most.
I think things are more complicated than that, so I'll do some more research and ask professors as well.
Let me know if you have any other questions.
Thank you. What is the rate limiting enzyme in Protein synthesis, urea cycle, cholesterol synthesis, B oxidation. DNA and RNA synthesis
I'm not sure about protein synthesis as a whole, or DNA and RNA synthesis, but:
Urea cycle - Carbamoyl Phosphate Synthetase I (CPSI)
Cholesterol synthesis - HMG CoA Reductase
Beta oxidation - Carnitine Palmitoyl Transferase I (CPTI)
Thanks for this video. Why is frucfose1,6bp downregulated by amp? I thought if there's less energy the body would want to produce glucose to make more?
Good question! Remember that we need to propel glucose through glycolysis to get to pyruvate to make ATP, which is what our body uses for energy. If we just made more glucose and never actually ended up using it, we would die without sufficient ATP.
Sure, but the fruc-1,6-bp does in fact go on to react with aldolase, complete glycolysis and become 2 pyruvates, go through tca, etc, then atp gets made, right? so the amp would mean there isnt enough atp, and for that reason the body would want to make atp, and so amp shouldnt downregulate f-1,6-bp, right? Am i missing some key detail here? Thanks for your time
Ok I could be wrong but here is how I view it:
Gluconeogensis is to turn pyruvate into glucose the opposite of glycolysis.
For glycolysis, it makes sense that AMP would activate and stimulate glycolysis and that ATP would inhibit
So it should be the opposite for gluconeogenesis: ATP should activate it and AMP should stop it
@@isabeldeangelis276 that’s exactly how I think about it as well!
I love you
See ya in chemistry!:)