 In this module, we will discuss how protein molecules interact with each other and what forces what happens when forces which are keeping proteins in a specific shape are disrupted. So let's talk about how proteins interact with other molecules or other proteins. Proteins carry information to interact with other molecules other proteins for example in two forms the shape of the protein and the chemistry which is present on the surface of the protein. The shape of the protein is important because if it is to interact with another protein the two shapes have to be mutually compatible sort of like jigsaw puzzles fitting together. So we can see in our slide that these two proteins are interacting with each other so groove of one protein is fit the bump of one protein is fitting in the groove of another adjacent protein just having a compatible shape complementary shape is not enough complementary chemistry is also very important for example the site at which these two proteins are going to interact have to have compatibility to in this side for example if you notice the positively charged group of atoms or positively charged entity is interacting with the negatively charged entity in this case a hydroxyl group is interacting with the positively charged our group of amino acid on another protein right below it is also a right below it there is I'm sorry let's raise this right below it there's a hydrogen bond you can see hydroxyl group is interacting with the hydrogen atom forming a weak interaction called hydrogen bond which we have discussed in a previous module there's also another type of bond which we haven't discussed yet it's called the hydrophobic bond this bond is between those two these two molecules right here you can see these two molecules they're interacting and that they're interacting via hydrophobic bond all these interactions are very weak but because they their number is great these weak interactions can stabilize interaction of two proteins just as you're familiar with Velcro the type of material which is present for example in tying up shoes it are it is based on weak interactions but many many interactions that make it possible for two things to bind together it's the same principle let's look at protein denaturation protein three-dimensional shape is based on the chemistry of different R groups within that protein there their shape of a protein can be disrupted at extreme temperature I'll give you a very common practical example when you boil an egg protein present in the egg denatures and when you cool it you never form you never go back to the original state so if we heat the protein we disrupt these weak interactions that I just talked about and when the protein is allowed to cool down they don't always form the same interactions proteins precipitate out that's what happens for example when you boil an egg so when you boil an egg the protein is denatured it is no longer in its original shape and it cannot fold back to its original shape and it precipitates out it's no longer soluble some proteins however are soluble there are many examples we will talk about it later on in this course you can heat these proteins and these proteins carry the information of folding in a three-dimensional way within themselves so when you heat these proteins they loosen up but when you cool them down they again adapt their original structure but not all proteins can do that however it's important to know that protein three-dimensional structure can be disrupted some proteins can revert back others cannot