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0:01
All right everybody, we are back this week and starting on our first of three weeks focused on metabolism in various microbes. So this week we are going to be doing just a general introduction to metabolism in bacteria and kind of compare it to some other living organisms. And then we are going to look at the beginning stages of breaking down carbohydrate molecules. In later weeks, we'll
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get into the other types of biomolecules that can be broken down, as well as other types of getting energy. So this week we are doing chapter 8.1 and 8.2. So I just popped the learning objectives at the beginning of each section in here. But let's start off with a just quick overview of metabolism in general. So generally when people hear the word metabolism they think of breaking things down. You
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eat food, you break it down. And that's how you get energy. And that is true. But that's not the entire story. Metabolism includes both breaking down and building molecules. So we have two subtypes of metabolism. The first is catabolism. This is what most people associate with the word metabolism. These are when we take large molecules like the foods that we eat, and break them down into significantly smaller ones. And this is going to release energy. So we're making energy, um,
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to get it so that we can use that energy for other purposes. This type of metabolism is also referred to as ex organic. Generally, when we are talking about these types of reactions in living things, um, sometimes you'll see the word exothermic pop up here and there, um, which still this is breaking things down and releasing energy. But the thermic part of that refers to heat. So exothermic reactions are going to release heat. And sometimes extra organic and exothermic are
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going to release both energy and heat, like with our cells. Um that is part of how we keep our body temperature is this process of metabolism is going to release heat, whereas other living organisms, um, sometimes are not going to release heat at all or very much heat. Sometimes it's not going to be enough to actually measure accurately. And in which case they're just considered xorg.conf.
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So they are releasing energy. The flip side of this is anabolism. This is when small molecules are assembled into significantly larger ones. So this is how we take amino acids and make them into proteins, and how we take those, uh, monosaccharides like glucose and fructose and assemble them into larger, more complex carbohydrates. So this process requires energy to be added to that equation in order to assemble those who building things takes energy.
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So these are called enter organic. So that end um enter and doe refer to in taking something in. So inorganic is using that energy. Taking the energy in endothermic would be requiring heat in order to make that reaction go. Um so we don't see that a ton in biochemical processes. So in living things um, but we see that outside of living things very, very commonly taking a cake is one example.
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You can mix all of the small molecules, all of the ingredients together, but if you don't add heat, you end up with just a mix of all of your ingredients, um, with no reactions happening. So organisms, all living organisms, not just microbes, can be classified by where they get their energy and where they get their carbon from. So we have two main groups chemo troughs and photo troughs. Chemo troughs are going to get their energy from chemical sources of some sort.
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Photo troughs are going to get their energy from light sources. And some way we can further break down both of these classes into autotrophs and heterotrophs. Auto means self. Hetero means different, um or other. So an autotrophic is going to be some sort of living organism that can basically create its own energy. It can take those chemicals and actually create the energy. Um, usually this is going to be converting carbon dioxide into some other carbon compounds. Um,
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heterotrophs again, hetero is other um or different. So these organisms are going to rely on complex organic compounds um provided to them usually from autotrophs. So common autotrophs from the chemo group. So these are chemo autotrophs. When you add those together. These are also sometimes referred to in the microbial world as litho troughs. These are going to be bacteria that can oxidize hydrogen, sulfur ion nitrogen and carbon monoxide. Um so they're going to
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break down all of those. Chemo heterotrophs also sometimes known as organo troughs in the microbial world. These have to get their carbon source from inorganic from organic compounds. So all animals, including us. So we are chemo heterotrophs. Most types of fungus out there, this includes both molds and yeasts. We'll kind of touch on that again a little bit later in the semester. Protozoa and some types of bacteria. These are going to be the vast majority of bacteria. Um,
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the other groups that we see listed here are very, very specialized groups of bacteria under the photo troughs. Photo autotrophs are going to take light and some sort of chemical, um, in organic compounds and create their own energy. So these are going to be all plants, um, algae, cyanobacteria. And then there are green and purple sulfur bacteria, which are kind of cool organisms. Photo heterotrophs again need those organic compounds. So these are going to be
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green and purple non sulfur bacteria and a class called healio bacteria. So we're not going to look at a lot of these types of bacteria in too much detail in this class. Class. Most of the bacteria that we're going to be focusing on are chemo heterotrophs, because a lot of those bacteria are the ones that are human pathogens. So that's kind of what we care most about in a pre medical field. Um microbiology class. Some of these other bacteria, like cyanobacteria and certain
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types of algae can be problems for humans. They're just not quite as common as are known pathogens. Okay. So we are going to talk about redox reactions. So hopefully this sounds at least somewhat familiar from past chemistry courses. So. Transferring electrons um, in living things. This is done via hydrogen ions. So the hydrogen, um, is going to have an extra electron. So it has a negative charge. Transferring these electrons between molecules is
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what ultimately provides energy to the cells. It's a lot more complicated than that. We're going to get into a little bit of detail here um, in a bit. But that transfer of electrons, plain and simple, is what is going to lead to energy production for the cells. Now this makes a very steady and safe source of energy because if a any living organism bacteria us, anything, um, is going to take all of the nutrients that they get, feed it into some sort of catabolic reaction and try
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to extract all of the energy all at once. It would be incredibly dangerous and would most likely kill that organism, because it would be such an immense amount of energy produced. And in our case, it would also mean a ton of heat. Um, in our body can only handle so much heat, which is why fevers can be really dangerous. But by doing this energy production, um, using these very, very small, um,
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multi-step processes, we get to gain our energy very steadily and very safely. So there are two types of transfer and electrons oxidation. This is when, um, an electron is removed from a particular molecule. And reduction reactions are when that electron is added to some sort of molecule. So those are donor and acceptor molecules. But these two types of electron transfer have to work together. Because you can't just take an electron off of a molecule and leave it floating
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out in space. Um, that's that's not going to work. Um, so oxidation and reduction reactions always work together because you got to if you're to take an electron off of something, you got to put it on something else. So these go hand in hand. You will never find one without the other.
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Now within living things, there is, um, a group of molecules that are specially designed to transfer these electrons around. So from catabolism, energy gets stored in either ATP molecules, which I'll talk more about here in a little bit. Or a group of molecules called electron carriers. Now electron carriers are molecules that can be very, very easily reduced or oxidized. So they're really, really good for these metabolic process pathways because we can oxidize or reduce. So add
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or remove electrons really really really easily without a ton of energy needing to be put into it. Because theoretically you can remove electrons from just about any molecule out there. Some of them are going to take way more energy to do that than others. So these molecules do not take hardly any energy. Um, this is a very favorable reaction. So there are three primary electron carriers. Um, these are common to both us humans and two bacteria for the most part. So the first group
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is nicotinamide adenine dinucleotide, abbreviated as NAD. So when we have NAD with that plus versus NAD H, that H again is representing that hydrogen that I mentioned on this slide. So that hydrogen ion remember carries a negative charge. So now we come look at this. So NAD plus once you add that negatively charged hydrogen ion to it now it has a net zero charge. So that's where that NAD h is coming from. And we lose that charge. You'll see that repeatedly in um a lot of these
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electron carrier molecules that this last one that I'll get to in a moment is a little bit different. But these are the main, um, carriers. So NAD and NAD are. One of the most common, um, carrier molecules that we are going to see in the cell. So these are the oxidized and reduced states of this particular molecule here. The NAD next is nicotine adenine dinucleotide phosphate. So this is basically the NAD molecule with a phosphate added on to it. But we see the same
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thing happening. We can have a positive charge. And if we add that negatively charged hydrogen ion we get that net zero charge. And then our last one, this flavin AD nine dinucleotide fad or FAD H two. This one's a little different. As you can see the charges are um different than that. Uh the NAD and NAD pH molecules. So this fad, this is the oxidized form, um, and then reduced is going to be a fad H2. So this structure, we don't need to get into all of the inner details of
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this. But these are not going to have charges to them. Right. Generally, they are not represented that way in writing because this this molecule's a little different than when we have the nicotine, uh, nicotine based receptor. Um, all of these are going to kind of come from various sources. Um, we've got to build these somehow. But these are very, very similar to our nucleic acids. So ATG and C that's used to, um, produce our DNA. So these are the three primary electron carriers
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in their oxidized and reduced states. And then our other one that I mentioned is ATP stands for AD adenosine triphosphate. This is basically metabolic money. This is the preferred energy source for living organisms. And it's a really really nice way for so for a cell to store energy very very safely and release it only when needed. Right. So the core molecule here is a m p. So adenosine mono phosphate which would just be this right here. It's we've got our adenine molecule
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here we've got a ribose. So a sugar molecule linked to this first phosphate group right. So that's adenosine monophosphate. If we were to cut right about here that's a pretty stable molecule. AMP is very very stable. It's very happy. But then when we start adding other phosphate groups on through a process called phosphorylation, they don't get along quite so well. So this p sub I represents inorganic phosphate um which is a single one of these groups. So
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it's going to have oxygen and hydrogen in it too. But these phosphate groups they're really bulky. They're going to take up a lot of physical space. And each phosphate group carries a negative charge to it. And that does not change when we start linking them together. So we've got this phosphate molecule with a negative charge. We've got another one with negative charge. So if we were just looking at these pieces here that's adenosine di phosphate. So di for two phosphate
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groups add that third one on. And now we have adenosine triphosphate. So these phosphate groups they don't want to be this close to each other. They'll stay there. Again this is a safe way of storing energy. But this bond is also broken very very easily. Um, because those phosphate groups don't really like each other. So removing a phosphate group is called D phosphorylation. So we can go from ATP to ADP. That's very, very common. We don't see a MP a whole lot. Um, because
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we're kind of constantly cycling through these molecules, adding and removing phosphate groups.
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So like I said, this is a continual process. So going through um the catabolic processes. So getting energy um getting our nutrients, breaking that down to produce our energy is going to um create ATP. And then the flip side are anabolism. So building things is going to um, take off one of those phosphate groups and create ADP, therefore gaining energy to make those new bonds to create those larger molecules.
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So there's two main ways to make ATP. I'm not going to go into a ton of detail on both of these right now. We'll get into, um, a lot more of the nitty gritty details as we go through this week and the next couple of weeks, but these are the two. Um, substrate level phosphorylation. This is making and breaking of chemical bonds. So an example of this is creation of ATP. Oxidative phosphorylation. This will be one of our main topics next week. These are redox reactions.
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So reduction oxidation reactions tied to a enzyme called ATP synthase. This is through cellular respiration. Again we'll get into a lot of details about this next week when we finish up cellular respiration. Um we will talk a bit about substrate level phosphorylation a bit later today. Okay. So those are electron carriers and they're all involved in a lot of reactions within a cell. And one of the important things that all living things have like us in bacteria are enzymes. These
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are molecules that are catalysts and speed up biochemical reactions. All enzymes are proteins. Um, so proteins have tons and tons and tons of functions within living things. One of those functions is enzymes. And enzymes function by lowering the amount of energy needed to form or break chemical bonds and do that reaction conversion. So enzymes are actually not used up in the reaction. So they just kind of come in and assist with the process. And then they can
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go back to the start and continue. They're very reusable molecules. So if we've got this reaction shown here in the red line that's a lot of energy required to get that reaction. Just start. But if we add an enzyme in the amount of energy required to make that reaction happen is dramatically lowered. Each enzyme and how much they lower the activation energy is a little bit different, but they are going to lower it so that that reaction can happen a lot more easily. Sometimes
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without the enzyme, reactions just happen because there is no way for whatever living organism it is to actually get that reaction to go without the assistance of an enzyme. So enzymes are going to bind to the substrates. So whatever they are going to act as a helper molecule, um they bind at something called an active site. This kind of fits together like a jigsaw puzzle. So there's very, very specific patterns. So one enzyme is not going to bind to
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any substrate out there. These are very very specific pairings of substrates and enzymes. There are some enzymes out there that can bind bind to multiple substrates. But it's still usually only going to be a small handful of substrates. They're not going to be able to bind to every single other molecule out there. So super, super specific to help with this process. So the substrate is going to bind into that active site of the enzyme. The active site specifically
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is on the enzyme not on the substrate. The enzyme is where you find the active site. So once that binding happens, the enzyme is going to change shape just a little bit because the molecular interactions here are going to change slightly change the 3D structure of the molecules in those areas. Um, but that means that these stay tightly linked for the duration of the reaction process. So then
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the sub street gets broken down or built into whatever products, and then the products leave the active site of the enzyme and the enzymes available to help with the very next reaction. Now enzymes can be altered. Their function can be altered by environmental conditions like p h. So every enzyme has an ideal pH range, so it can't be too acidic or can't be too basic for them to function. Um, outside of that range, the enzymes can denature remember
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their proteins. So all of those larger level structures can start to break down and then the enzymes no longer work anymore. Next um, thing that can alter enzyme reaction um is substrate concentration. So if there's more substrate there is more enzyme activity, um, because there's more stuff for the enzymes to bind to and then temperature. Um, this is a slightly more unique one. So just like each enzyme has an ideal temperature range that it functions best at,
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um, very, very small increases in temperature will generally increase enzyme activity. Um, so make it a go a little bit faster, but there is a limit to that. So if the temperature goes too high, just like if the pH is too far outside of its range, um, the enzymes will also denature, whereas if the temperature goes too low, then the enzyme reaction rate is going to very dramatically slow down or stop altogether, depending on how far outside of that ideal range that you find
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the temperature. So some different results with temperature changes. Um, it has the most unique, um, effect on enzymes, but generally speaking enzymes function. They're best in conditions that are best for whatever organism is going to produce them. So the enzymes that we humans produce are going to function best around, uh, about 94°F, up to about 100°F, because, again, average body temperature is 98.6. That is average on everybody. Each person has their own unique, um,
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normal temperature range. Um, but enzymes that we humans produce are going to function best around 98.6°F. A little over a little under is going to be totally fine. Whereas if we were to try to share our enzymes, say, with some sort of animal like an Arctic fox, let's say, um, I don't know what their normal body temperature is, but I would assume it's probably a lot higher than ours. I'd
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have to look that up. Um, but our enzymes aren't necessarily going to function very well on them. So further than that, there are certain enzymes that are not going to work very well or work at all unless they are bound to another helper molecule. Um, so we have two types of helper molecules. These are cofactors and Co enzymes. And they each have slightly different um definitions. So cofactors specifically are in organic
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ions like iron and magnesium that are going to help stabilize the structure and function of that enzyme. So that's what conformation means a structure. So an example of this is the enzyme DNA polymerase which is what creates does the copying of new strands of DNA. It absolutely requires a zinc iron bound to it in order to function without that zinc ion. It is not going to do its job. Now
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coat enzymes. On the other hand, these are organic helper molecules also required for enzyme action. So examples of these are those electron carriers that we saw earlier. NAD nad fad. All of those um are going to be Co enzymes among some other examples that we'll see. So these generally come from our diet. So most of these cofactors and Co enzymes we have to get from our diet. Um frequently these Co enzymes um they are either going to be the actual
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vitamins themselves that act as Co enzymes and others are going to be precursors. So um, the starting stage of a coenzyme that needs a little bit of processing to be created. We also where there's enzymes, where there's a reaction, there's generally a way to block it. So enzyme inhibitors are going to block or reduce enzyme activity. We have two main classes of these competitive inhibitors and non competitive inhibitors. So a competitive inhibitor is any
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molecule any inhibitor molecule that is so similar to that substrate that that enzyme is looking for that it basically looks exactly like the substrate to the enzyme. And combined with the enzyme which blocks the actual substrate from being able to get in there and bind. So one example of this is sulfa drugs. These are a type of antibiotic. Um, these are going to bind to an enzyme in the folic acid
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synthesis synthesis pathway within bacteria which prevents the production of folic acid um, which is a really, really, really important um precursor to making DNA, RNA and proteins. So that's how that class of antibiotics work. And then noncompetitive inhibitors, they're not blocking the enzyme. They bind somewhere else. That's not the active site. This is called the allosteric site. And this triggers a conformational change or structural change which
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makes the enzyme less attracted to the substrate. So I've got a little graphic up here from the textbook. So that competitive inhibitor just blocks the substrate from coming in, whereas the noncompetitive inhibitor binds somewhere else. It binds to that allosteric site. And now that active site changes shape. And so then the substrate doesn't recognize it and is not going to be able to bind. So you still have inhibition just through a different means. So one example of
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this that impacts both us humans and bacteria is cyanide. So this binds to an enzyme in the electron transport chain which we'll talk about next week and ultimately prevents the production of ATP our energy currency. So that's kind of how cyanide, um, kills things is, is we stop making energy and then everything stops happening in our cells. On that depressing note. Moving on. Um, other enzyme interactions. So we can have allosteric activators. So they are also going to
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bind to an allosteric site, something that is not the active site. But these are going to increase enzyme activity. So they make that enzyme work more. And then feedback inhibition. This is going to be very similar to like a negative feedback loop that um applies in our body where, you know, if we're trying to maintain that thyroid hormone concentration, too much of that is going to signal
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back to stop making the production molecules. Um, so similar idea here. So the products of the reactions that the enzyme is helping to speed up those products kind of get fed back into this loop and kind of says, hey, we don't need as much of this being produced now, so slow it down. And that wraps up 8.1. We will continue in the next video on chapter 8.2 and talk about breaking down carbohydrates.
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