in this article we're gonna talk about the structure of proteins and what basically is a protein a protein is a polymer consistent of many amino acids so each amino acid represented by the circle is a monomer that forms the protein whenever you have many amino acids is also called a polypeptide and the bond that connects each individual amino acid residue is a peptide bond so let's talk about the individual structure of an amino acid so an amino acid has a chiral carbon with a hydrogen attached to it and it has an amine group attached to it as well and then it has an R group and a carboxyl group now I'm going to draw another amino acid right next to it the left side where the nitrogen is located is the n-terminal of the amino acid the right side that has the carboxyl group is the c-terminal of the amino acid now these two amino acids can react with each other in a condensation reaction where we're going to lose water and we're going to connect the two amino acids into one molecule so once water is removed we could form a peptide bond this is also called a dehydration reaction because you're losing water and so this is going to be the new product of the reaction so let's see if I can fit it in here so this oxygen is gone so now we have a nitrogen let me take out h2o we have run hydrogen left over we lost to once we lost water so this is a dipeptide because we have two amino acids combined and so this a my bond that we see here and that is the peptide bond we formed a bond between the carbon and the nitrogen atom so whenever you combine two amino acids to form a peptide bond you're forming a covalent bond which is hard to break now let's talk about the different levels of protein structure there's four levels that you need to know the primary structure the secondary structure the tertiary structure and finally the coronary structure now the primary structure is simply based on the sequence of the amino acids found in the protein the sequence determines the shape of the protein if you replace just one amino acid with another it will completely change the shape of the protein so the shape and its function is primarily determined by the sequence of amino acids the secondary structure describes the localized shape of a protein and there's two of them that you need to be familiar with the Alpha helix and the beta pleated sheet in the Alpha helix you could see that it stabilized by hydrogen bonds the NH group of one amino acid interacts with the carbonyl group of another amino acid and each turn contains about 3.6 amino acid residues now here is a visual illustration of the beta pleated sheet just like the Alpha helix it too is stabilized by hydrogen bonds between the carbonyl group of one amino acid and the NH group of another amino acid next up we have the tertiary structure which represents the three-dimensional complete folding pattern of the protein and so here's the visual illustration of it so we could see some areas it's just a straight chain here we have an alpha helix and here we have a beta pleated sheet now the tertiary structure is one individual subunit when you combine multiple subunits you create a quaternary structure so hemoglobin is an example of that it has four individual subunits two alpha subunits and two beta subunits so hemoglobin is a protein with a coronary structure and so that's basically it for this video hopefully it gave you a basic understanding of proteins and the four levels of structure that they have thanks for watching
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