hi everybody dr mike here in this video we're going to take a look at an overview of metabolism and i think the best way to do this is to address the key points and terms that you'll be assessed on in a metabolism and biochemistry exam and these terms have popped up in the box here so we're going to cover in around about 10 to 15 minutes these points which often take two or more hours in a lecture so we're going to look at glycolysis glycogenesis glycogenolysis gluconeogenesis those words are starting to sound the same now krebs cycle electron transport chain lipogenesis lipolysis ketogenesis and ketolysis let's start where do we begin we begin with a delicious cheeseburger you take that bite and you ingest it we know that cheeseburgers are going to contain all those important macronutrients those macronutrients include carbohydrates so carbs they include proteins and they include triglycerides so let's write that down triglycerides so the fats so we've got our carbs our proteins and our fats that we've now introduced into our gastrointestinal tract importantly you should be aware that carbohydrates are simply made up of carbons hydrogens and oxygens proteins are made up of carbons hydrogens oxygens and nitrogen and triglycerides are made up of carbons hydrogens and oxygens much like the carbohydrate so your question may be well what's the difference well for carbs the amount of carbons and oxygens are in a pretty much an equivalent ratio but for triglycerides the carbons and the hydrogens far exceed the amount of oxygens and it's actually this reduced number of oxygen is the reason why triglycerides don't like water all right you've ingested it into the gastrointestinal tract in your mouth the saliva contains an enzyme called amylase that breaks down the carbs into your micronutrient version of this macronutrient which we're going to focus on here which is going to be glucose and let's write that glucose as g the proteins once that hits the stomach you've got hydrochloric acid that unfolds these proteins but you've also got pepsin which is a protease molecular scissors that starts to chop it up so we digest those proteins into amino acids amino acids and we'll write that as a a and then once we hit these small intestines the very first part called the duodenum with the help of bile to break it down a little bit and lipases the enzyme that breaks down fats we now release or produce i should say glycerol and fatty acids so both glycerol and fatty acids together make up triglycerides now what's happening this is in the gastrointestinal tract still once it reaches the intestines the glucose will get absorbed into the bloodstream specifically the portal system that goes to the liver the proteins or i should say the amino acids there that have been digested they get absorbed at the small intestines also into the bloodstream specifically that portal system as well going to the liver but the triglycerides being broken down into glycerol and fatty acids they actually get absorbed not into that bloodstream they get absorbed into the lymphatic system and that lymphatic system will distribute the glycerol and fatty acids to different tissues of the body but also it ultimately ends up in the liver as well so that's why i've drawn up this monster liver here because the end of the day all these micronutrients are making it to the liver what happens metabolically to them let's first start with glucose when glucose enters the liver it can undergo a couple of different things one we can store that glucose and we store that glucose in the form of glycogen so you can store the glucose as glycogen now that's important because now glucose glycogen glucagon glycerol all these words sort of sound the same remember this if it ends in o g e n it means it's stored and it's inactive so glycogen is the stored and active form of glucose and this process of storing glycogen from glucose is called glycogenesis glycogenesis glycogenesis let's have a look here right glycogenesis that genesis means the beginning of glycogen genesis it's the beginning of glycogen so we're storing that we can also take that glycogen and split it apart to release glucose if we like to and this process of taking the glycogen splitting it apart back into glucose is called glycogen olysis the term or suffix lysis means to split apart so that's called glycogen olysis splitting it apart so now we've got free glucose now this free glucose if we want to utilize it to make energy in the form of atp this is what it does the glucose will turn into something called pyruvate and the process in which glucose turns into pyruvate is called glycolysis so we've already covered a couple of things here we've covered glycogenesis we've covered glycogenolysis and we've covered glycolysis the first three pyruvate what does pyruvate do pyruvate will enter the mitochondria and in the mitochondria it will turn into something called acetyl co a let's draw the mitochondria up we know it's this double membrane structure that's super important for us so let's draw that up there's one membrane and now let's do the other membrane there we go an outer membrane and an inner membrane now once acetyl coa is in that mitochondria with the help of its best friend oxaloacetate it undergoes this cycle where it produces a whole bunch of substrates and this is called the krebs cycle it's got many names it's not just called the krebs cycle it's also called the tricarboxylic acid cycle and the citric acid cycle but let's just write krebs cycle here we've skipped gluconeogenesis we'll get there i promise what's the whole point of this krebs cycle why are we taking glucose through glycolysis through krebs cycle ultimately because we want to produce two important things we want to produce nadh and we want to produce fadh2 what do these two things do well in this mitochondrial inner membrane you're gonna have a couple of important proteins and channels one two three four and then i'm going to draw a last one like this this is called the electron transport chain and the reason why is because the krebs cycle and even glycolysis to a degree right even glycolysis will produce nadh what these things do is they hold on to hydrogen ions and they hold on to electrons that's important and when they hold on to these things once they're produced they will release those electrons they will release the hydrogen ions and what happens is the electrons will get thrown through this chain from one to the next like a little game of hot potato with these electrons hence why it's called the electron transport chain cha-ching right there it's passing it i'll stand over here it's passing it from one side to the next and in doing so it produces the capacity of some of these proteins to take hydrogen and throw them across the membrane into the into membrane space take some of that hydrogen throw it into this space now what's going to happen we're going to accumulate hydrogen in this space and the hydrogen diminishes here so there's a concentration difference a lot of hydrogen here not much hydrogen here so this hydrogen wants to go down its concentration gradient and it does so here through this thing called an atp synthase so piggybacking on the energy of the hydrogen ion diffusion this thing produces atp it produces huge amounts of atp so at the end of the day the whole point of us having this glucose is to undergo this process to produce all of this atp brilliant but something i didn't mention is that in order for this to happen we need oxygen oxygen needs to be utilized in this process if we don't have oxygen we can't produce atp through this electron transport chain it's called oxidative phosphorylation so sometimes you'll do really vigorous intense exercise really quickly like a 100 meter sprint or jump into the gym and lift some weights really hard and really fast and you want to create more atp than oxygen available so think about it you go through this process goes like this you've got this but we need oxygen we don't have enough you can't breathe enough of that oxygen in enough oxygen can't be delivered to the mitochondria fast enough so it goes uh backs up backs up backs up to this pyruvate and so the pyruvate goes that's all right i'll figure this out now we used to think that the pyruvate turned into lactic acid lactic acid and because the definition of an acid is something that releases hydrogen ions right and then produces its relevant base which is lactate we used to think that this is the process and it's those hydrogen ions that give us that burning sensation when you do that type of exercise but now what we're thinking is this isn't the case we don't really think that there's that lactic acid that's being produced we think that it's actually lactate that's directly being produced and we're not releasing hydrogen ions the lactate can actually absorb those hydrogen ions and buffer them out so lactate may actually be the friend in this process amazingly once we've got enough oxygen back into the system the lactate can reversibly turn into pyruvate wonderful all right now the whole purpose of doing this is it actually so when i say we produce nadh for example we actually produce it from something called nad plus nad plus goes to nadh what this process does of going from from pyruvate to lactate is it actually produces some nadh nad plus for us which is good because we can use that here in the process of glycolysis for example and then going backwards it produces nadh which can be utilized to produce energy here in the electron transport chain all right now we've spoken about this process we haven't even touched upon amino acids glycerol and fatty acids where do they fit in well it's a beautiful process when we bring these amino acids in and you know there's heaps of different types of amino acids right i said that for glucose if we don't produce energy we store its glycogen what about amino acids well we don't really store excess amino acids we deaminate it and we pee it out as urea right we deaminate it into ammonia peed out as urea some amino acids will be synthesized into proteins but other amino acids will actually jump into depending on remember there's like 20 different types of amino acids some will jump into glycolysis some will jump into the krebs cycle awesome glycerol and fatty the glycerol that comes in what does that do well it can jump into glycolysis that's pretty cool and the fatty acids that come in they can jump into the krebs cycle so the triglycerides glycerol fatty acids can feed into glycolysis feed into the krebs cycle and help produce atp the amino acids can do the same help produce atp why would we need to use these when we've got glucose well we use these when predominantly we don't have any glucose that's available we've used all our glucose stores or intentionally not using glucose think about this when we don't have glucose glycolysis isn't happening there's not enough pyruvate there's not enough acetyl coa oxaloacetate goes well i've got nothing to bind with i can actually jump out and start to produce more pyruvate here i can try and produce some glucose through this process right so that means oxaloacetate it diminishes but if you're doing that you're producing acetyl coa and now you don't have oxaloacetate to bind to so acetyl coa levels start to go up when you don't have any glucose and what does that mean well if you've got accumulating and sorry for all these arrows if you accumulate all this acetyl coa they actually snap together like lego blocks and they produce something called ketones what do ketones do ketones can jump out of the liver into the bloodstream go to the brain and what's it going to do in the brain it turns back into acetyl coa and when it turns back into acetyl-coa you can undergo this process this process of turning acetyl coa into ketones in the absence of glucose right because again what happened no glucose no pyruvate no acetyl coa oxaloacetate goes well let's try and make some glucose from from me jumps out but then the acetyl coa that's produced doesn't have its friend to bind with so accumulates snaps together forms ketones like beta-hydroxybutyrate and this process is known as ketogenesis that's one of the words in the box right ketogenesis where's that down here ketogenesis now once the ketones get out of the liver cross the blood-brain barrier go to the brain and turn into acetyl-coa this is called ketolysis we're now splitting apart the ketones into acetylchola ketolysis oxaloacetate isn't the only thing that tries to replenish this lost glucose have a look amino acids are trying to replenish this lost glucose jumping into various aspects of glycolysis and krebs cycle glycerol is trying to do the same as well and fatty acids are jumping into the krebs cycle here at the level of acetyl coa this process of taking amino acids glycerol and to some degree fatty acids these are non-carbohydrate-based sources but we're trying to produce glucose here or at least glucose substrates this is called gluconeogenesis so this process here and here predominantly and a little bit here but also through ketones this is called glucose neogenesis now gluco means glucose neo means new genesis means the beginning of read it backwards the beginning of new glucose glucogen neogenesis is the beginning of new glucose from non-carbohydrate-based sources like amino acids and fats brilliant now the last thing we haven't spoken about is lipogenesis and lipolysis very simple i said what happens when you have excess glucose or does glycogen excess amino acids peed out as urea or can feed into this system glycerol and fatty acids what happens when you have too much of that well they can bind back together again right they can come back together to form the triglycerides and we can store those triglycerides in the liver this is known as lipogenesis which makes sense right i've defined genesis now lipogenesis is the formation of lipo right lipo what's that lipids right triglycerides lipogenesis and then splitting it apart and going in the opposite direction here going in that opposite direction that's going to be lipolysis breaking apart so let's write lipolysis as well and so what we've done here is hopefully helpfully we've gone through all these important points that you get assessed on in biochemistry metabolism exams and assignments for example and we've run through an overview of metabolism i hope that helps hi everyone dr mikey if you enjoyed this video and want to watch more please hit the like and subscribe button