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Current time:0:00Total duration:10:44

Non-enzymatic protein function

Video transcript

okay so we're going to be talking about non-enzymatic protein function and before we get into what exactly that means let's just say we are playing game of Scattergories in the next the next category that comes up is protein and you have to list all the different types of protein that you know and so you're like oh I totally got this we got beef and and pork and chicken right those are different types of protein and that's true but what about the biochemistry type of protein as in the large biomolecules that are made up of amino acids what what are all the different types of proteins then and so that's a little bit tougher and so that's the point of what we're going to be talking about today is to talk about all the different types of proteins and the different functions that they that they perform and so the key to understanding proteins as we go forward is understanding one unique characteristic about proteins and that unique characteristic is that they can bind various biomolecules and they bind specifically and tightly and so just keep that concept in mind as we're talking about all the different functions of proteins and and that will help you understand how they are able to perform the vast array of functions that they do so I like to think of proteins as being in one of two main classes there are the enzymatic proteins so enzymes and then the non enzymatic proteins or that we'll just call them the non enzymes and so let's back up just a minute what exactly are enzymes what what do they do and enzymes are in a nutshell little chemical reaction machines they can catalyze all sorts of chemical reactions so they catalyze reactions that help to sustain life and so they're really the workhorses of the cell helping to build up and break down things as needed and by acting as catalyst and science can help to accelerate the rate and specificity of these chemical reactions and one good example of this that you're probably familiar with already is DNA polymerase which catalyzes the synthesis of new strands of DNA and probably even more familiar to you are the enzymes in your saliva so every time you eat there's one enzyme in particular called amylase which is responsible for breaking down starch into sugars so amylase is another example of a proto protein that has enzymatic function and just notice for a second that both of these enzymes and in a s e ace and so in general if you see protein and and has this sort of ending you should be thinking to yourself oh I bet this is an enzyme an enzymatic protein so that's a good rule of thumb now non enzymatic proteins or non enzymes are all those proteins that carry out functions that require the capacity to bind but not necessarily to catalyze a reaction and so what are some examples that we'll be talking about of non enzymatic protein function well there are proteins that function as receptors or ion channels in a cell membrane and we'll talk more about that and then there are proteins that are transport proteins there are also motor proteins and then a special class of proteins that function as an integral part of the immune system and those are called antibodies and so we'll go through each of these examples of non enzymatic protein function one by one so let's give ourselves a little bit more room to talk about those now let me quickly interject that it's important to realize that not all proteins are always either an enzyme or a non enzyme oftentimes they have characteristics of both and so just keep that in mind as I'm going through and highlighting the non enzymatic properties in this video ok so starting with receptors and ion channels there are certain proteins that exist in the membrane of a cell and function as either acceptors or ion channels now receptors are proteins that receive or bind a signaling molecule so let's draw a cell here we're going to draw the membrane bilayer here and so here would be my exterior of the cell and here's the interior of the cell and within this membrane bilayer you can find a receptor protein so we'll draw that here and this receptor protein will bind a signaling molecule also known as a ligand ligand which then induces some sort of chemical response in the cell so one example of a receptor protein and ligand pair is an insulin receptor and insulin so let's say this ligand is insulin and this is the insulin receptor now insulin is a hormone that's released by the pancreas in response to an increase in blood glucose levels so let's say there's extra glucose because you just ate a piece of pizza or something so let's say there's an increase in glucose around and then insulin is going to be released by the pancreas in response to this increase in blood glucose and then once it's released it binds to its corresponding receptor on certain cells which leads to a cascade of signals within the cell and this allows it to then absorb this excess glucose into the cell and then likewise you can also have an ion channel that also spans the membrane bilayer so let's extend this lipid membrane bilayer and then we'll draw in an ion channel protein here and so likewise this protein spans the entire bilayer of the cell and it acts as a pore or a channel through which certain ions say calcium and enter or exit the cell so it can come in and come out through this same channel okay so next step are the transport proteins and now these proteins are responsible for binding small molecules and transporting them to other locations in a multicellular organism like humans and the trick with these proteins is that they have to have a high affinity for their ligand when the ligand is present in high concentration so at high concentration of a ligand you have high affinity of the protein for that ligand and at low concentration you have a low affinity and a great example of this is hemoglobin so hemoglobin is present in red blood cells and it picks up oxygen in the lungs so here are my lungs it's high in oxygen in your lungs and then delivers this oxygen to tissues and will draw tissue here say it's muscle tissue where it's present and low concentrations and so this is a great example of a transport protein at work so next up are the motor proteins which include myosin kinesin and dynein all of which are capable of generating great forces and these proteins are really crucial for cellular motility and myosin specifically is a protein responsible for generating the forces exerted by contracting muscles so every time you flex your bicep like so your myosin protein and your muscles are contracting and generating that force now kinesin and dynein are motor proteins that are responsible for intracellular transport and then dining in particular also plays a role in the motility of cilia which are these little extensions of a cell that project out and mutations in a particular dining protein can lead to a rare disease called primary ciliary dyskinesia so in primary ciliary dyskinesia you can see there's some sort of dyskinesia or problem and movement for the cilia and mutations in a particular dining protein lead to this rare disease in which the action of the cilia of the cells lining the respiratory tract failed a function and this leads to a decrease in mucus clearance from the lungs and therefore an increased susceptibility to chronic infections like pneumonia bronchitis so as you can see these motor proteins are really important and then finally our last class of non enzymatic proteins that we'll be talking about are the antibodies of the immune system now antibodies are protein components of the adaptive immune system whose main function is to bind foreign antigens and target them for destruction so in this case the antigen which comes from any foreign substance say a virus or something like that is the antibodies ligand so here's an example of an antibody and then here is the antigen and the antigen is really just the antibodies particular ligand so you can think of antibodies as being like little red flags for the body's immune system letting us know that hey this thing is not supposed to be here we need to get rid of it somehow and it's important to know that an antibodies affinity for its target antigen is extraordinarily high so the affinity is strong really high and so there you have it you can see all the different types of non enzymatic roles or functions that proteins can play either as receptors or ion channels as transport proteins motor proteins and then highly specific antibodies in our immune system