in nature we have four major classes of biomolecules and so far we discussed two of these four major classes so we focused on proteins and nucleic acids now we're going to move on and discuss the third class of biomolecules we call carbohydrates or simply sugars now in nature the organisms use sugars for a variety of different ways and in this lecture we're going to briefly discuss four different roles that sugars actually play now there are many different types of sugar molecules but the major sugar molecule that we use inside our body is glucose now where does glucose and in generally where do sugar molecules actually come from well sugar molecules are produced by plants and plants basically capture that energy that is stored in light that comes from the sun and it transforms that energy into the chemical bonds within the sugar molecule so what happens is in the sun we have all these different nuclear reactions which take place and produce they release energy and that energy is then stored in electromagnetic waves which propagate through space and some of this electromagnetic radiation eventually makes its way to the Earth and to the plants on Earth and so what these plants do is they take the carbon dioxide in the atmosphere that's the carbon source and then they take the water found in the soil and they use the energy stored in light they combine these two reactants to produce these products so the sugar molecule as well as oxygen that we then breathe and use on the electron transport chain in the process of aerobic cellular respiration so essentially when we ingest these carbohydrates which are produced by plants for instance when we inest bread products or pasta products and so forth we essentially ingest carbohydrates which are derived and produced by plants and so once we ingest these carbohydrates our body breaks down these carbohydrates into their individual monomer sugars and if this monomer sugar is not a glucose molecule we typically transform that into a glucose molecule because it's the glucose that we use in the process of glycolysis and aerobic cellular respiration to basically produce the high energy ATP molecules that we use inside our body and if we already have too many of these ATP molecules if we have enough the glucose can be stored in the form of glycogen for later use so ultimately what happens is that energy that is produced in the nuclear reactions is basically stored in these chemical bonds Within These sugar molecules and we when we ingest these sugar molecules we essentially take that same energy that came from the Sun and store it in the ATP molecules and use those ATP molecules to carry out all the different types of processes that take place inside our cells so we see that the first role that sugars play is basically energy storage and fuel source so we use these sugars to basically carry out different types of reactions by using these ATP molecules that ultimately came from the glycolysis process the breakdown of glucose now the second role that sugars play is actually being present in nucleic acid such as RNA and DNA molecule in fact ATP adenosine triphosphate itself contains a ribos sugar so we have these RNA DNA molecules which are nucleic acids and what that means is they basically play the role of storing genetic information and Passing genetic information down from one individual to The Offspring now these RNA and DNA molecules basically contain sugar components in the case of RNA we have the ribos sugar in the case of DNA we have the deoxy ribos sugar and deoxy simply means on the second carbon we don't have a hydroxy group so if we take a look at the following molecule so if this base is let's say adenine then this molecule would be that ATP molecule that we spoke of earlier so we have the triphosphate group we have that nitrogenous base and these two groups are essentially connected to one another as a result of this sugar so this is a ribo sugar that Bridges these two molecules and every single RNA molecule basically contains this group here this unit now the next function of sugars the next role that sugars actually play in organisms and this includes inside our own bodies is using sugars to basically modify lipids and proteins and we'll discuss this in much more detail in the next several lectures so basically we can diversify the capabilities and the functionality of proteins and lipids by basically attaching sugar components onto these macro molecules so by combining sugars and proteins and sugars and lipids and so forth we can basically increase the capabilities of these molecules for instance we already spoke about an important glycoprotein when we discussed the coagulation Cascade so we discussed the tissue Factor so we said that the tissue factor is basically a glycoprotein so this is shown in green and this is let's say the cell membrane of some endothelial cell found in the blood uh in the blood vessel so what this tissue Factor does is it's actually a glycoprotein that basically interacts with other molecules namely Factor 7 to form a DI complex and this glycoprotein this tissue fact is actually used to initiate the blood clock and Cascade the formation of the blood clot more specifically it initiates the extrinsic pathway of that coagulation Cascade and we have many many many different types of examples of ways in which we can actually modify proteins as well as lipids and thereby diversify uh their function thereby increase their capabilities and functionality now the final thing I'd like to mention about sugar molecules is that in plant as well as in bacterial cells sugars actually make up the components are are components of cell walls and cell walls are very important because they serve very a very very important function so they basically protect the cell they also give the cell structure they act in communication and also in transport and we'll discuss this in much more detail when we'll focus on plants and the process of um photosynthesis