[Applause] [Music] welcome to topic two which is all about molecular biology we know that biology is the study of life so when we bring molecules into the mix we are looking at the many types of molecules that we find in living systems molecular biology explains living processes in terms of the chemical substances involved and trust me when i say that living processes have a lot of chemical substances this area of study can be a bit difficult to wrap your head around because all of the components are extremely small and similar in scope to what you would learn in a chemistry class the easiest way to remember all of these tiny components is to relate them back to a larger biological concept which is exactly what we will do together let's get started when we look at all life that we know of it is based around one specific element called carbon point to any living thing you see plant animal you name it and carbon will be there carbon is the backbone of molecules found in living organisms because of its structure which allows for a stable molecules to be built around four covalent bonds it has four outer valence electrons which means that it can chemically bind with up to four other atoms filling out its valence shell with eight total electrons an example of this is methane which has a chemical formula ch4 one central carbon and four hydrogen atoms chemically bound to fill the outer electron shells of the carbon and each hydrogen atom when compounds are built around carbon and generally contain hydrogen we call them organic compounds methane is an example of a very simple organic compound but again this ability for carbon to bind with up to four other atoms gives it the ability to create a large variety of stable compounds which are the building blocks of all living organisms carbon can create many different compounds but there are four in particular that are extremely important for building life that we see on our planet these four compounds or macromolecules are carbohydrates lipids proteins and nucleic acids we will discuss each one of these in greater detail in later videos but for now let's look at a few specific differences between them starting with their chemical makeup carbohydrates are molecules that contain only carbon hydrogen and oxygen they have a specific ratio of oxygen to hydrogen atoms within them which is always one to two so for every oxygen atom we see there should be two hydrogen atoms we can count them in this sample structure which has six total oxygen atoms and 12 total hydrogen atoms examples of carbohydrates are sugars starches and cellulose and are used for short-term energy storage and to build important structures in plants among other things lipids are molecules that also only contain carbon hydrogen and oxygen the difference here is that they do not follow the one to two ratio with oxygen and hydrogen in our example here you can see that there are a few oxygen atoms with a large number of hydrogen atoms examples of lipids are fats oils waxes and phospholipids and cholesterol and they are used for long-term energy storage and cell boundaries proteins are molecules that are made up of carbon hydrogen oxygen and nitrogen they follow a general structure with their building block which is called an amino acid that has a nitrogen bound to a central carbon which is bound to another carbon n c c there are other important components that branch off of this base structure that we will talk about in the future examples of proteins include enzymes and they are used to regulate cellular processes and build cell structures nucleic acids are made up of carbon hydrogen oxygen nitrogen and phosphorus their base unit is called a nucleotide which we will talk a lot more about later examples of nucleic acids include dna rna and atp and are generally used for carrying information or energy as stated before organic compounds are those that contain carbon and generally hydrogen and are commonly used in biological systems the four different macromolecules discussed on the last slide are all classified as organic compounds though they are not the only molecules that make up the group when we look at inorganic compounds then we are first looking for any compound that does not contain carbon which would immediately classify it as inorganic but there are some examples that do contain carbon like co2 but are still classified as inorganic it contains carbon but it does not contain any hydrogen so therefore it holds the inorganic classification being able to tell the difference between macromolecules is important but it's also important to understand how they are used within reactions in the body at any given moment there are billions of chemical reactions taking place in the human body many of these reactions use enzymes which are specialized proteins to help speed up the reaction which we will cover later in more detail to keep this very complicated concept put in simple terms we call this collective sum of enzyme reactions metabolism the basics of metabolism help the body and the cells found within our body tissue create materials to use for cellular functions and also break down materials to create energy which is also used for cellular functions let's break this down in more detail on the next two slides metabolism can be broken down into two general processes the first one anabolism describes how smaller simple molecules can be chemically bound together to build larger more complex molecules this anabolism process in relation to building large organic molecules occurs through a specific type of reaction called a condensation reaction this works when a smaller molecule generally called a monomer is joined together with another monomer creating what we call a polymer from one unit mono to many poly recall that all four of our macromolecules are based around carbon hydrogen oxygen and a few other key elements so when these monomers are put together they reallocate their bonds to push out two hydrogen atoms and one oxygen atom and if you know a bit about inorganic chemistry you should know that two hydrogen atoms and one oxygen atom create water h2o this is a condensation reaction because it bonds the two monomers together and creates or condenses a water molecule as a product we build up macromolecules with anabolism but we break them down with a different process called catabolism catabolism is a process that explains how larger macromolecules are broken apart into their monomer components to be used for a cellular function or to be rebuilt into a different larger molecule again the cool thing about this process is that it is the exact opposite of anabolism to split these larger molecules apart water is used and consumed in the process breaking the connecting bond and using the two hydrogen atoms and one oxygen atom from the water to reform the original bonds seen in the monomer form this process is called hydrolysis the prefix hydro refers to water and lysis describes components being separated or broken apart anabolism and catabolism are never ending processes happening in the body breaking down and building up molecules as needed by each and every cell do [Music] [Music] you