Krebs Cycle | Made Easy!

Transcript Search in video 0:00 hi everyone Dr Mark here in this video 0:02 we're taking a look at everyone's 0:03 favorite the Krebs cycle also known as 0:05 the citric acid cycle also known as the 0:08 tricarboxylic acid cycle so take your 0:11 pick and let's go 0:16 the best place to begin is a quick recap 0:19 of glycolysis and in the process of 0:22 glycolysis we simply took a six carbon 0:25 molecule called glucose in actual fact 0:28 it's C6 h12 0:32 06 and the whole purpose of glucose is 0:36 to pull it apart rearrange it to pull 0:38 off hydrogen and electrons and in this 0:40 process of going from glucose down to 0:42 two three carbon molecules called 0:45 pyruvate 0:48 again this process is known as 0:50 glycolysis 0:52 feel free to watch the glycolysis video 0:55 that I've recorded in this process 0:57 multiple steps we ultimately produced 1:00 two molecules of nadh and two molecules 1:04 of ATP 1:08 now the whole purpose of this cellular 1:10 respiration so glycolysis Krebs cycle 1:14 then the electron transport chain is to 1:16 produce ATP either directly or to 1:19 produce ATP indirectly via nadh or fadh2 1:24 I'll talk about that in a second so this 1:26 is our net gain from the process of 1:29 glycolysis keep that in mind now we've 1:32 created a three carbon molecule called 1:35 pyruvate in actual fact we've created 1:37 two of them from one glucose molecule 1:39 and this pyruvate wants to enter the 1:41 mitochondria so it can enter the Krebs 1:43 cycle the mitochondria has an inner and 1:45 outer membrane it can't get through it 1:47 needs to be transformed into something 1:49 that can this is the product here it's 1:52 called acetyl COA 1:54 so we've got acetylcholai that pyruvate 1:57 needs to turn into how does pyruvate do 2:00 this well as you can see it goes from 2:01 being a three carbon molecule to a two 2:04 carbon molecule so it needs to lose a 2:06 carbon second thing is it needs to add a 2:08 COA as well why do we snap color so 2:12 kawas coenzyme a why do we need that 2:14 well it's a coenzyme so when it's added 2:17 to carbon chains it helps transport that 2:20 carbon molecule and facilitate that 2:23 carbon molecule by being utilized by an 2:25 enzyme in this process snapping the 2:27 Calais allows the acetyl to enter the 2:29 mitochondria and be utilized by the 2:31 enzyme here to create a molecule called 2:33 citrate talk about that in a sec so what 2:36 do we need to do we need to 2:38 lose a carbon and we lose that carbon in 2:41 the form of carbon dioxide we need to 2:45 gain a COA 2:47 and in addition to this we need to take 2:50 an NAD plus and we need to turn it into 2:54 an n a d h plus hydrogen ions now this 2:59 is probably the most important step or 3:02 steps in the Krebs cycle and cellular 3:04 respiration let's talk about this for 3:07 two seconds 3:08 what is happening in this process well 3:10 ultimately NAD plus steals hydrogen from 3:14 these carbon molecules how does it occur 3:16 what is hydrogen hydrogen is the first 3:18 atom on the periodic table it is made up 3:21 simply of a positive proton in its core 3:23 and a negative electron flying around 3:25 the outside that's hydrogen you can see 3:27 it's neutral because the positive proton 3:29 is balanced by the negative electron now 3:31 if I take NAD Plus 3:34 and I still a hydrogen I'm simply 3:37 turning NAD plus into 3:39 nadh plus because it's neutral and it 3:43 started with a positive it's still going 3:45 to retain that positive so let's steal 3:47 one more hydrogen but this time let's 3:50 just pluck the electron from it and keep 3:52 that if I do that it then becomes nadh 3:55 and all I'm left with is a positive 3:57 proton now another way that you can 3:59 write a positive proton is h plus 4:03 so if I still 2 hydrogen from a molecule 4:06 I get nadh plus h plus 4:11 that h plus we know is what makes 4:14 something acidic beautiful so what we're 4:17 doing effectively is NAD plus is 4:20 stealing two hydrogen it takes a whole 4:22 hydrogen with the positive and the 4:24 negative and it takes one more hydrogen 4:26 but in actual fact just plucks the 4:28 electron off it and leaves the positive 4:30 proton out in the solution that's what 4:33 this equation is saying You must 4:36 remember that because that means this 4:37 molecule here is carrying hydrogens and 4:40 it's carrying electrons which we'll be 4:42 using in the electron transport chain 4:45 here's an important point that no one 4:46 ever talks about 4:48 play around with these carbons and to 4:49 produce carbon dioxide here we need a 4:52 vitamin B derivative called thiamine 4:55 pyrophosphate thiamine 4:59 Pyro 5:03 phosphate also known as TPP thymine 5:06 pyrophosphate is a derivative of vitamin 5:08 B1 so you need Vitamin B1 for pyruvate 5:12 to go to acetyl-coa 5:14 kellen's I'm a for that to snap on we 5:16 need another B vitamin derivative called 5:20 pantophenic acid 5:24 pantothenic 5:26 acid pantothenic acid is actually a 5:28 vitamin B5 5:31 derivative so we need Vitamin B5 here in 5:34 addition to that nicotinamide adenine 5:36 dinucleotide which is what NAD is that 5:39 is a derivative of niacin niacin is 5:42 vitamin B3 so simply in this one step 5:46 going from pyruvate to acetyl-coa we 5:49 need three B vitamins this is the reason 5:51 why our B vitamin complex is important 5:55 for cellular respiration now we haven't 5:58 spoken about the enzyme here the enzyme 5:59 in this process 6:01 is actually called pyruvate 6:06 dehydrogenase and we know it's going to 6:08 be a dehydrogenase 6:11 because when you transform NAD plus to 6:15 nadh or fad into fadh2 it's going to be 6:19 a dehydrogenase enzyme so now I've got 6:22 acetyl COA two carbons one COA enters 6:25 the mitochondria and what happens is the 6:27 acetyl-colla the two carbon will bind to 6:30 a four carbon molecule there's four 6:32 carbon molecule is called oxalo 6:35 acetate sometimes written as o a a and 6:41 create a six carbon molecule two plus 6:43 four equals six this is called citrate 6:47 and in this process we obviously lose 6:50 that Calais 6:55 we don't need it anymore I told you COA 6:57 is required to help move carbon uh 6:59 molecules around the place so they can 7:01 be utilized by their enzymes so we lose 7:04 that Co a and when we lose a COA we 7:06 usually use a synthase or a synthetase 7:09 and in this point here it's going to be 7:11 citrate 7:13 synthase 7:15 that's the enzyme that we use to snap 7:18 acetyl-coa together with oxaloacetate to 7:20 form our six carbon molecule citrate 7:23 citrate needs to rearrange itself so we 7:26 rearrange some carbon atoms we keep it 7:29 as a six carbon molecule and because 7:31 we're rearranging it we call it ISO 7:34 because it's changed ISO citrate 7:38 and the way we rearrange it is we lose 7:40 some water in the process then we gain 7:43 some water in the process and we use an 7:46 enzyme called aconitase to do this whole 7:49 thing 7:51 foreign 7:53 times now we have isocitrate isocitrate 7:57 the six carbon molecule needs to turn 7:58 into a five carbon molecule called Alpha 8:02 ketoglutarate 8:04 Alpha 8:05 Keto 8:09 glutamate 8:11 so we lose a carbon how do you think we 8:13 lose that carbon we lose that carbon in 8:15 the form of 8:18 carbon dioxide 8:19 now the enzyme that does this is called 8:22 isocitrate 8:23 dehydrogenase I'm going to write that 8:25 down what does that tell you ISO 8:29 citrate 8:32 dehydrogenase I told you something about 8:34 dehydrogenases they're used anytime 8:36 we're going to be using NAD Plus or fad 8:39 to steal hydrogen and electrons and 8:41 that's what's Happening Here NAD plus 8:44 turns into 8:47 nadh plus a free proton in the solution 8:51 so now we've got Alpha ketoglutarate a 8:54 five carbon molecule it needs to turn 8:55 into a four carbon molecule going to 8:58 lose a carbon again and gain a COA so I 9:01 think I've seen this before if we lose a 9:04 carbon in the form of carbon dioxide but 9:07 we gain a COA here that looks very much 9:11 like what's happening here with the 9:12 pyruvate dehydrogenase that's exactly 9:15 what's happening we're using another 9:17 dehydrogenase here and we also turn NAD 9:20 plus into nadh so same thing 9:24 NAD Plus 9:26 going to 9:28 nadh plus hydrogen ion so it's a 9:31 dehydrogenase what do you think it's 9:32 called Alpha ketoglutarate dehydrogenase 9:36 Alpha Keto 9:41 glutarate 9:43 dehydrogenase 9:46 now look again remember we're using B 9:49 vitamins here right we're using a B 9:50 vitamin here B3 derivative there we're 9:54 using for coenzyme a we need to use B5 9:58 pentothenic acid we need to use B1 10:00 thymine pyrophosphate here B3 again so 10:04 look how important the B vitamins are in 10:06 their derivatives just in the Krebs 10:08 cycle so now we've got this molecule 10:11 here which we haven't spoken about what 10:12 it's called Alpha ketoglutarate once it 10:14 loses a carbon gains a COA it's called 10:16 succinyl COA 10:20 succinol 10:23 COA succinyl COA needs to pop that co-a 10:27 off to Simply turn into something called 10:29 succinate 10:32 and in this process of popping that co-a 10:35 off 10:37 it actually releases a little bit of 10:39 energy and in this process of releasing 10:41 that energy we can actually turn either 10:44 ADP into ATP or GDP 10:50 into GTP again just another energy 10:52 molecule but think about it if that GTP 10:55 has a phosphate it might be able to just 10:57 give that phosphate to ADP 11:01 to now create 11:03 ATP 11:04 so we can create ATP in this process a 11:07 little bit of inorganic phosphate is 11:10 added in this process 11:12 two now because we lost a COA here like 11:15 we lost a COA here I said it's either a 11:17 synthase or a synthetase here it's a 11:19 synthetase so it's succinyl COA 11:21 synthetase 11:24 succinol 11:26 COA 11:30 synthetize now we're left with succinate 11:33 so here's the thing succinate turns into 11:36 Fumarate 11:39 which turns into malate 11:43 which turns into oxaloacetate succinate 11:45 Fumarate malate oxaloacetate all right 11:48 so to go into they're all four carbon 11:50 molecules here so what's happening in 11:52 this process so to go from succinate to 11:54 Fumarate what we need to do 11:57 is still some more 11:59 electrons and still some more hydrogen 12:01 ions how do we do that well this time 12:04 we're not stealing it using NAD plus 12:06 we're stealing it using f a d now 12:10 there's no plus here so we're stealing 12:13 two hydrogen right so f a d h 12:19 that's what we're creating two because 12:21 we're still in two hydrogen so we go 12:23 from fad to fadh2 and the enzyme that 12:26 we're using is another dehydrogenase 12:28 like I said called succinate 12:32 dehydrogenase 12:35 something 12:37 now we've got Fumarate Fumarate turns 12:40 into malate using an enzyme called 12:42 fumarase 12:45 fumarase and in doing so it 12:49 adds a little bit of water 12:51 now to go from malate to oxaloacetate we 12:55 use an enzyme called malate 12:56 dehydrogenase malate 13:00 dehydrogenase 13:03 dehydrogenase tells you it's either 13:04 going to use NAD Plus or Fad in this 13:07 case it's n a d plus again 13:11 forming n a d h plus hydrogen ions and 13:16 now we're back to the oxaloacetate so 13:18 what have we done just in the Krebs 13:20 let's not focus on this part here what 13:22 have we created remember 13:24 we have two pyruvate from one glucose so 13:26 simply one glucose molecule created two 13:28 pyruvate which created two acetyl-coa 13:31 which is created two of everything 13:34 so let's have a look let's first have a 13:36 look at carbon dioxide we've got two 13:38 there because remember two of everything 13:40 two four 13:43 that's it four so 13:45 we created four 13:47 carbon dioxide in the Krebs cycle let's 13:50 have a look now nadh 2 13:53 4 13:55 6. we created six 13:59 nadh what about fadh two 14:03 of them 14:05 two f a d h 14:09 two and what about ATP directly two 14:15 ATP so what we've created just in the 14:18 Krebs cycle is four carbon dioxide jump 14:20 into the bloodstream breathe it out no 14:22 problem but we've created these hydrogen 14:25 and electron character these are 14:27 carrying remember hydrogen ions and 14:30 electrons this is what we need for the 14:31 next step which is the electron 14:33 transport chain and ATP directly which 14:35 we can use to produce well to do work 14:38 basically so a final Point well this is 14:42 the Krebs cycle in its most direct 14:44 process something that you should 14:46 probably understand is that 14:48 you can actually feed things into the 14:50 Krebs cycle and take things out at 14:52 different areas so for example you can 14:54 feed amino acids in to the Krebs cycle 14:57 or change some of these uh substrates uh 15:01 into amino acids so for example Alpha 15:03 ketogliterate can turn into various 15:05 amino acids and various amino acids can 15:07 turn into it same down here with the 15:09 succinate some same with other different 15:11 areas you can add feeding and remove 15:13 amino acids that's a really important 15:16 Point amino acids can feed in and out of 15:19 the Krebs cycle if we look at fatty 15:21 acids as a potential energy source we 15:24 can feed fatty acids into acetyl COA 15:26 acetyl-coa can actually turn into fatty 15:28 acids and fatty acids can turn into it 15:30 so here's where fatty acids can come in 15:33 now importantly and I'm going to do a 15:36 whole video on this but this is 15:37 important process what if we don't have 15:38 any glucose so somebody is intentionally 15:41 starved themselves of glucose maybe 15:43 Atkins diet or maybe they're doing 15:46 something where they just want to eat 15:47 fats for whatever reason that may be 15:49 they ingest all these fats but there's 15:51 no glucose 15:52 so what does that mean well it means 15:54 that's not happening that's not 15:56 happening right 15:58 oxaloacetate actually has the ability to 16:02 jump out turn into malate and turn into 16:05 glucose oxaloacetate is my point is can 16:08 ultimately turn back into glucose so if 16:10 you don't have any glucose in the body 16:11 the body wants it so much that it pulls 16:14 oxaloacetate out to turn into glucose 16:16 now if you don't have any oxaloacetate 16:19 here right let's just say this is this 16:21 part here it's gone right 16:25 the acetyl COA has nothing to bind to 16:28 now remember I said that fatty acids 16:31 if you're ingesting fats but you're not 16:33 ingesting glucose they can turn into 16:35 acetyl COA 16:37 so we've still got acetyl COA feeding 16:39 into the crabs but no locks allow 16:40 acetate for it to bind to so this 16:42 process doesn't happen 16:44 so acetylcholai simply accumulates and 16:46 when you accumulate acetyl Cutlery it 16:48 snaps together to form ketones 16:51 this is 16:53 what is it ketogenesis so the ketones 16:57 can then jump out into the bloodstream 16:58 go to the brain where the brain has 17:00 plenty of oxaloacetate now this hot this 17:02 is happening in the liver remember the 17:04 liver 17:06 the brain is not making ketones the 17:08 liver is so the oxaloacetate isn't 17:11 jumping out to create glucose in the 17:12 brain the oxaloacetate is fine in the 17:14 brain so once the acetyl COA in the form 17:17 of ketones jumps into the brain it can 17:19 turn back to acetyl-coa and undergo the 17:21 Krebs cycle that's how the brain uses 17:24 ketones for energy anyway that's an 17:25 aside I hope that you enjoyed this video 17:28 of the Krebs cycle also known as the 17:31 citric acid cycle also known as the 17:32 tricarboxylic acid cycle hi everyone Dr 17:36 Mike here if you enjoyed this video 17:38 please hit like And subscribe we've got 17:40 hundreds of others just like this if you 17:42 want to contact us please do so on 17:44 social media we are on Instagram Twitter 17:46 and Tick Tock at Dr Mike tadarovich at 17:52 d-r-m-i-k-e-t-o-d-o-r-o-v-i-c speak to 17:54 you soon 17:55 foreign