[Music] in this video we will study about the beta oxidation of fatty acids beta oxidation is a catabolic pathways of fats in which free fatty acids are converted to acetyl-coa since this process involves oxygen in one form or another it is known as oxidation but why is this process called beta oxidation a farts are stored in the human body in various forms and one of the major storage form are the triglycerides triglycerides compose of a single molecule of glycerol which is attached to 3 molecules of fatty acid it is important to understand the structure of a fatty acid here are two images that depict the chemical structure of fatty acid it consists of a long chain of carbon and hydrogen atoms which is denoted as our this side chain is attached to the functional group the carboxyl group which is C double o H now we know that the our side chain consists of single chain of carbon and hydrogen atoms let's expand this chain a bit the carbon atom that is directly attached to the functional group is known as the alpha carbon and the carbon atom next to the alpha carbon is the beta carbon in beta oxidation of fatty acids the our chain is broken down between alpha and beta carbons and hence the name Vita oxidation let's have an overview about the process of beta oxidation the human body contains adipose tissue which consists of triglycerides the triglycerides contain fatty acids and glycerol molecules the fatty acids are distributed all over the human body and from there they enter into the blood to the blood they are distributed to virtually all the cells of the body that can metabolize fatty acids the vati acids then move inside the cytoplasm of the target cells in the next phase the fatty acids enter into the matrix of the mitochondria after crossing the inner and outer mitochondrial membranes in the final phase the fatty acids are metabolized oxidatively inside the mitochondrial matrix so the whole process of beat oxidation can be divided into three phases a transport of fatty acids from the adipose tissue to the target cells we entry of the fatty acids into the cytoplasm and then into the mitochondria of the cells and see oxidative catabolism inside the mitochondrial matrix so let's first talk about the transport of free fatty acids from adipose tissue to the target cells like we just discussed the human body contains fats which have adipose cells in them the fats are located in main areas like abdomen thighs and arms the adipose cells contains triglycerides which have glycerol in combination with three free fatty acids the combination of glycerol with free fatty acids is important because glycerol has a large molecular mass which prevents the escape of free fatty acids from adipose cells here the enzyme lipase comes into play which breaks the bond between glycerol and free fatty acids once his bond is broken the free fatty acids can enter into the bloodstream and virtually reach any cell of the body that is able to metabolize free fatty acids now there are two tissues in the body that cannot metabolize free fatty acids which are the RBC's and the nervous tissue both of these tissues have one thing in common that they lack mitochondria and mitochondria are essential for fatty acid metabolism
so here is a target cell that is able to metabolize free fatty acids with the help of mitochondria the free fatty acid first enters into the cytoplasm of the cell through a special protein called fatty acid transporter the free fatty acids have a net negative charge and they cannot cross the membranes of the cells as such and they require special transporters to cross the membranes in the next step the free fatty acid must enter into the matrix of the mitochondria after crossing its outer and inner mitochondrial membrane the matrix of the mitochondria is important because it contains all the enzymes that are required for the beat oxidation of fatty acids as well as the enzymes for Krebs cycle and electron transport chain before the free fatty acid can be transported into the mitochondrial matrix it must be activated so let's talk about the next part that is the activation and transport of free fatty acid inside the target cell mitochondria so first talking about the fatty acid activation a free fatty acid must be converted into its active form that is the SI l Kawai SI l co is the only form that can be metabolized inside the mitochondrial matrix this reaction is catalyzed by the enzyme si el Kawai synthetase and in this reaction a molecule of ATP is converted into mono phosphate and a molecule of pyrophosphate is released coenzyme a is also essential for this reaction this reaction takes place at many sites in the cell including the outer mitochondrial membrane the endoplasmic reticulum and the peroxisomes the fatty acid activation is very very essential because without the activation the fatty acids cannot be utilize as such in the mitochondria now once activated the free fatty acids are then transported into the mitochondria let's understand this transport in a bit detail so on one side we have the cytoplasm of the cell we have the outer mitochondrial membrane and the inner mitochondrial membrane the space between them is known as an inter membrane space and on one side we have the matrix of the mitochondria the outer mitochondrial membrane contains these small pore like structures called porins which make the outer mitochondrial membrane very permeable to many substances including SI l co e so SI l co a can freely transport inside the inter membrane space after crossing the outer mitochondrial membrane but after that the inner mitochondrial membrane is not permeable so we require a special mechanism to transport the s I'll go a through the inner mitochondrial membrane into the matrix this mechanism is called the carnitine shuttle now the carnitine shuttle contains many enzymes and one of them is the carnitine palmitoyl transferase one located in the outer mitochondrial membrane the main job of the enzyme carnitine palmitoyl transferase one is that it attaches a molecule of carnitine to as'll cuy in this reaction the coenzyme a of SI l co a is released back into the cytoplasm and volleyer of s I'll contain is generated inside the inter membrane space in the next step the enzyme carnitine as'll carnitine translocase which is located on the inner mitochondrial membrane transports this acyl carnitine into the matrix of the mitochondria but like we just discussed si el coche is the only form of the fatty acid that can be metabolized inside the mitochondrial matrix so it must be regenerated this job is done by the enzyme carnitine palmitoyl transferase 2
this enzyme attaches coenzyme a again to the asylum molecule and regenerates the carnitine back the carnitine that is regenerated back is transported again into the intermembrane space that can be utilized by the carnitine palmitoyl transferase one you can see in this illustration that the enzyme carnitine as'll carnitine translocase transports one molecule of carnitine into the intermembrane space and in exchange of that it transports one molecule of acyl carnitine into the matrix of the mitochondria so this is how the free fatty acid is transported into the mitochondrial matrix up till now we have studied the transport of free fatty acids from adipose tissue to the target cells we have also studied about the entry of free fatty acids into a cytoplasm and mitochondria in the next part of the video we will discuss in detail about the oxidative catabolism that happens inside the mitochondrial matrix so for a complete understanding of the beta oxidation topic make sure to watch that video if you found this video helpful make sure the support met simplified by hitting the subscribe button below and also make sure to like this video thank you so much for
In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, and NADH and FADH2, which are co-enzymes used in the electron transport chain. It is named as such because the beta carbon of the fatty acid undergoes oxidation to a carbonyl group. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although some fatty acids are oxidized in peroxisomes.
Fatty acid catabolism consists of:
Activation and membrane transport of free fatty acids by binding to coenzyme A.
Oxidation of the beta carbon to a carbonyl group.
Cleavage of two-carbon segments resulting in acetyl-CoA.
Oxidation of acetyl-CoA to carbon dioxide in the citric acid cycle.
Electron transfer from electron carriers to the electron transport chain in oxidative phosphorylation.
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