chapter 25 lecture 3 is on lipid metabolism lipids are transported mainly by in combination with proteins they're called lipoproteins and here you can see these green things on the outside these are proteins there's uh APO B 100 APO C2 apoe these are common um inside we're going to have non-polar lipids and then s surrounding them are going to be amphipathic lipids like phospholipids that have non-polar tails and polar heads there are four classes of lipo proteins they're kyom microns very low density lipoproteins or vldls low density lipoproteins those are ldls and high density lipo proteins which are hdls kyom microns have very little protein they form in the intestinal mucosal cells they transport exogenous or dietary fat and they contain a protein called apoc2 apoc2 activates an enzyme that allows the fatty acids inside the kyom Micron to be released for absorption by atopos and muscle and then whatever is left over the liver processes they enter into the Lacs they're carried into the systemic circulation into atopos where the triglyceride fatty acids are released and they're stored in the adipocytes and used by muscle cells for ATP production vldls have 10% protein and they transport endogenous triglycerides those are ones that we produce in um inside ourselves from liver to fat cells and they are converted to ldls ldls are 25% protein these are known as the bad cholesterol they're going to carry about 75% of our blood cholesterol to the body cells and they have a protein in them called apob 100 that's important because because it's a docking protein that binds to the receptor for receptor mediated endocytosis of the LDL and two cells hdls are the good cholesterol they're about 40% protein and they carry cholesterol from cells to the liver for elimination so we have two sources of cholesterol endogenous and exogenous endogenous is the cholesterol that's synthesized by the liver and exogenous is the kind we get from outside sources for adults the desirable levels of blood cholesterol are our total cholesterol under 200 migs per deciliter LDL under 130 migs per deciliter HDL over 40 migs per deciliter and normally triglycerides should be in the range of 10 to 190 migs per deciliter there's a number of different ways to try to reduce blood cholesterol if it's too high uh certainly exercise and diet are a good thing but also um there's a number of drugs that you can take if you have uh very high cholesterol levels there some of them are going to inhibit synthesis of cholesterol While others inhibit absorption of cholesterol so in our body the fate of lipids uh there are number of different Fates for lipids some can be oxidized to produce ATP so they can be broken down some are stored in atap POS others are used as structural molecules or to make essential molecules for instance phospholipids and the plasma membranes lipoproteins they transport cholesterol thromboplastin is uh important for blood clotting and milin sheaths speed up nerve conduction as well as cholesterol that's used to synthesize bile salts and steroid hormones triglycerides are stored throughout our body they're stored in atopos tissue we carry most of our excess fat in the subcutaneous layer um but we also carry it uh near the kidneys uh in the umum the greater momentum in particularly that fat apron that hangs down the front 15% in the genital area and 8% between muscles um the adapost cells have lipases that are going to catalyze both the deposition of fats from kyom microns and also break down neutral fats into fatty acid and glycerol fats in atopos are not inert so they are constantly being broken down and moved throughout the body triglycerides are split in fatty acids and glycerol and that's called lipolysis and hormones that influence it include epinephrine norepinephrine and gluc cortic oids um the glycerol and fatty acids are then broken down separately um as you can see here glycerol can be modified and enter into uh the substrate level phosphorilation or the gsis procedure the fatty acids can go through a process called beta oxidation and enter into the electron into the um as aetl COA into the kreb cycle in the um they can also be converted into Ketone bodies like aceto acetic acid beta H hydroxy butyric acid and acetone glycerol can be converted into glucose by conversion in glycer glycer aldhy 3 phosphate and as I said in beta oxidation carbon atoms are removed from pairs in pairs from fatty acid chains and the resulting molecules of of aceto COA and into the kreb cycle as part of the normal fatty acid catabolism two acetyl COA molecules can form something called aceto acetic acid and that can be converted into beta hydroxy butyric acid and acetone these are called Ketone bodies and formation of Ketone bodies is called ketogenesis the heart muscle and the kidney cortex prefer to use aceto acetic acid for ATP production conversion of glucose or amino acids into lipids is called lipogenesis and stimulated by insulin uh the inter intermediary links in lipogenesis or glycer aldhy 3 phosphate and acetyl COA so not only does insulin promote the uptake of fats and um carbohydrates and amino acids it's also going to cause any excess glucose or amino acids to be converted into fat please now our blood Ketone levels are usually pretty low and um many tissues do use Ketone for ATP production but if you have an excess of Ketone bodies you can develop ketosis which can cause acidosis in which case it's called keto acidosis and that's an abnormally low blood pH different things that can increase Ketone production would be fasting starving or eating high fat meals with few carbohydrates this is the case with the Atkins diet where you really severely limit carbohydrates and eat mainly fat and protein acidosis is an abnormally low blood pH and it can be detected quite often by the sweet smell of the Ketone body acetone on your breath this happens um sometimes with diabetics because triglycerides are used for ATP production instead of glucose because they can't take glucose up and since insulin inhibits lipolysis um they are going to be using um the fats as fuel so the goals for lecture three to describe each of the following the kyom microns my cells vldl HDL LDL listed two sources of cholesterol in our bodies list the normal ranges for blood cholesterol for LDL HDL um describe what can be done lower blood cholesterol levels and Define lipolysis lipogenesis Ketone bodies and keto acidosis