hi everyone and welcome to chapter 6 in this chapter we'll be talking about energy metabolism and enzymes so most of the energy that keeps all organisms alive really starts with the Sun or comes from the Sun as we can see producers like plants can capture the energy from the Sun through a process called photosynthesis and we'll talk about that more later on but some of that energy is lost in the form of heat producers can capture sunlight or the energy found in sunlight and use it to produce organic molecules like glucose which consumers will use once the plants and animals die or the producers and consumers die they are broken down or their molecules their organic molecules are broken down by decomposers which can Harvest some of the energy found in those chemical bonds but again some of that energy is lost in the form of heat bioenergetics is a study of energy flow through a living system and this can be an individual organism or it can be many organisms living together within a larger system so why do we need energy we need energy to go through our daily activities which really refers to metabolism within the cell or organism and metabolism refers to all of the chemical reactions that are happening within the cell or the living organism metabolism includes all of the building reactions and building is also known as anabolic reactions or anabolism and all of the reactions that are breaking down larger molecules into smaller molecules and those are called catabolic reactions or sometimes called catabolism so a metabolic pathway is a bunch of biochemical reactions that are happening to convert one or more substrates into some kind of final product and again these can be building reactions such as through photo photosynthesis and an example of an anabolic reaction or a series of anabolic reactions could be taking carbon dioxide and water these are small molecules and building a larger molecule such as glucose but these reactions can also be catabolic for example down here we're going to see this reaction in the next chapter this is the process of cellular respiration which is overall catabolic because we're going to take glucose the larger molecule and break it down into smaller subunits including carbon dioxide and water so again metabolism is really the sum of the building reactions the anabolic reactions and the breakdown or catabolic reactions when I look at anabolic reactions these always require energy input and you're building larger molecules from smaller ones and I can see that up here so I can see in anabolic reactions I'm taking smaller subunits with an input of energy and I'm building a larger molecule and in my catabolic reaction I can see that I'm taking a larger molecule and breaking it down into smaller subunits and energy is released in this case interestingly all types of living organisms share some common metabolic pathways and this tells us or provides evidence that all of us originated from a common ancestor but over time there are differences in these metabolic pathways that develop due to the development of specialized enzymes that allow these organisms to be Specialized or adapt to their specific environments interestingly though all organisms in these metabolic pathways ultimately will harvest energy from their environment for example from eating eating or consuming other organisms and breaking down chemical bonds to make some kind of ATP some kind of form of energy so that we can use the energy stored in this molecule to carry out other functions inside the cell so here I have two types of chemical reactions and I wonder if I show you this picture can you guys tell me which one is anabolic and which one is catabolic let's take a closer look so at the top I see I've got two smaller molecules and I'm linking them together to form a larger one I'm building so building is anabolic I think of sometimes anabolic steroids because I hear that a lot in the news I'm building and whenever I'm building larger molecules I'm going to have to put energy into the reaction so usually this is in the form of ATP and the bottom one I'm taking a larger molecule breaking it down into two smaller subunits so that must be breaking down and that would be a catabolic reaction and I know energy would be released energy would be released and usually I can capture that in the form of ATP what about the process of photosynthesis using light energy to synthesize so synthesize I'm building something what do you guys think would that be anabolic or catabolic I think the word synthesis kind of gives away that it's going to be a building or anabolic reaction overall and if I look at the overall equation for photosynthesis it kind of supports my answer I'm taking several carbon dioxide molecules several water molecules the energy from the Sun and I'm going to be building a larger glucose molecule and release some oxygen as well so overall this will be an anabolic reaction and we're going to see this in chapter 8 so what are the types of energies we have available to do work I know energy is the ability to do work and there are two types we have kinetic energy which happens when something is in motion or moving or we have potential energy when objects have a potential to move and in our book it gives us a link to a website that shows us something like a pendulum almost like a Grandfather's Clock and when the pendulum is swinging when it goes up during the motion there's kinetic energy but then it pauses up here and now there's no kinetic energy but high potential energy because it has the ability or potential to move back down so what are examples of potential and kinetic energy inside cells one example comes from chapter 5 when we were talking about diffusion remember diffusion is when molecules can move from a high concentration to the side where they have a lower concentration and here I see this when they're is a high concentration of a molecule in one side there's high potential energy for the molecules to move when they're actually moving I can see kinetic energy energy is released until the concentration of the molecule across both sides of the membrane is equal then there is just random movement across the membrane in the bottom example we have chemical energy chemical energy is stored in chemical bonds and a good examples at the bottom right I have this disaccharide that has energy stored within the chemical bonds that's a form of potential energy if I break the bonds that is energy that is released so that is kinetic energy and we usually capture that energy if we're not using it right away and store it in the form of ATP so that we can use it for something else we can use this energy to power some kind of other reaction in in the future our book also gives us the example of potential energy stored in the chemical bonds of gasoline and we can transform that into the kinetic energy that allows the car to race on a RAC trck so it looks like this is is that octane it looks like eight of them so we have Octane and we know that as we break the chemical bonds energy is released to power the movement of that car in biology whenever we're talking about energy in terms of how much energy do we need to build a larger molecule or how much energy is released when we break a larger molecule down into smaller subunits we're almost always talking about Gibbs free energy this is the amount of energy that's available to do work also known as AKA usable energy and this is after we account for the energy that was lost as heat we can calculate Gibbs free energy down here using this equation where change in G Delta G which is Gibs free energy the final Gibs free energy minus the initial Gibs free energy of the reaction is equal to the total energy or enthalpy of the system minus the energy that was lost as heat or entropy that was lost to Disorder so Delta G my Gibs free energy is again equal to the change in the total energy of the system enthalpy minus temperature in Kelvin times change in entropy which is Disorder so let's apply the Gibbs free energy equation to our chemical reactions in biology If energy is released in some kind of chemical reaction we call this an exergonic reaction and Delta G will be less than zero it'll be a negative number so how does this work let's look at the graph below all right I see Gibs free energy my starting point is here so that's my initial hibs free energy and my final energy value looks like it's down here so this is my final Gibs free energy value and I'm just going to put random numbers here let's pretend this is like 10 and appear this is 100 at this point right here so I can tell that GF minus G initial that's what is that 10 minus 100 and usually we have units of Jew per mole or kles per mole but I'm going to ignore the units right now I have minus 90 that's negative whenever you have a negative Delta G this is an exonic reaction because energy is released energy has been released and I can see that here as well I have a high energy value for my reactants some kind of reaction occurs over time and then energy has been released right here and here I have low energy at the end of the reaction exonic reactions are called spontaneous reactions because they will happen even if you do not put in any energy but one of the biggest mistakes that students make is they think spontaneous means fast and it does not does not mean fast sometimes these reactions take millions of years so as long as you don't have to put in energy and it still happens whether it takes a thousand years or a million years we still call it spontaneous so again spontaneous is not does not necessarily mean fast and then something I see a little hump right here we're going to talk about that in a bit that little hump is something called activation energy on this slide I see what looks like the mirror image of the previous slide if a chemical reaction requires an input of energy if you have to put in energy to get the reaction to happen then Delta G will be a positive value and these are called endergonic reactions so we're putting in some energy to get it to happen and if I use the same numbers I used earlier let's say this is the initial Gibs free energy and I'm going to use the same number 10 and this is the final Gibs fre energy and I used 100 earlier so let's see G final minus G initial that's Delta G so final is 100 I can see that's the products minus initial is 10 down here that would be a positive value so I can see that is an endergonic reaction I have more energy at the end of the reaction than when I started and again Delta G is greater than zero and again I see something over here that activation energy we'll talk about in a bit but I know that I had to put in energy to get this to happen and that makes a lot of sense if I pretend I have a ball here and I'm rolling it up the hill I need to put in energy to get the ball to go all the way down to the product side okay and this has nothing to do with Biology at all but this graph always reminds me of those bowling games that you see at carnivals have you guys ever played this game you have to like push the bowling ball just enough so that it goes here and it stays in the hump and it doesn't come back anyways this always reminds me of that bowling game I've never won before you guys can tell me how to win if you know the secret so here's that same picture when I was talking about anabolism and catabolism let's see which chemical reaction would be exergonic and release energy or have what would we say Delta G would be greater or less than zero EX xonic reactions are going to kind of look like this so I know G final will be lower than G initial so that would be less than zero so an exonic reaction is whenever we take a larger molecule chop it up and break it into smaller pieces because that will release energy energy will come out of the reaction so that would be the bottom one that would be an exonic reaction Delta G would be negative okay so that takes us to the end of our first video for chapter 6 in our next video we're going to be talking about activation energy that little bump we had to get through or get past before we could get to the product side of the reaction