University:
Blythewood High School
Course:
Biology
Academic year:

2023
Views:

72

Pages:

2
Author:

T. Cooperan

Lipid Metabolism Glycerol metabolism Glycerol as a result of lipid hydrolysis (triglycerides) can be an energy source. Glycerol is converted by cells into hydroxyacetone phosphate. This glycerol then enters the carbohydrate metabolism pathway, namely glycolysis. In the initial stage, glycerol obtains 1 phosphate group from ATP to form glycerol 3-phosphate. Furhermore this compound will enter the respiratory chain to form dihydroxy acetone phosphate. Calculation of Energy Results from Lipid Metabolism The energy produced by beta oxidation of a fatty acid cn calculated . For example, a fatty acid with 10 C atoms is available, so we need 2 ATP energy for activation, and the energy produced by beta oxidation is 10 divided by 2 minus 1, which is 4 times beta oxidation, meaning the result is 4 x 5 = 20 ATP. Because fatty acids have 10 C atoms, 5 acetyl-CoA are formed. Each acetyl-CoA will enter the Kreb's cycle, each of which will produce 12 ATP, so the total is 5 X 12 ATP = 60 ATP. Thus, a fatty acid with 10C atoms will be metabolized with a result of -2 ATP (for activation) + 20 ATP (result of beta oxidation) + 60 ATP (result of the Kreb's cycle) = 78 ATP. Half of the acetyl-CoA will turn into acetoacetate and it will turn again into hydroxy butyrate and acetone which known as ketone bodies whichc called as ketogenesis. And the process of converted acetyl-CoA into cholesterol called cholesterogenesis which can then be used as material to be synthesized into steroids (the process is called steroidogenesis). Synthesis of fatty acids Fatty acid synthesis is the opposite of the fatty acid breakdown pathway that occurs in mitochondria. Food is not our only source of fat. All organisms can synthesize fatty acids as long-term energy reserves and as constituents of membrane structures. In humans, excess acetyl CoA is converted to fatty acid esters. The synthesis of fatty acids corresponds to their degradation (beta oxidation). Fatty acid synthesis occurs in the cytoplasm. ACP (acyl carrier protein) is used during synthesis as a binding point. All synthesis occurs within the multi-enzyme complex-fatty acid synthase. NADPH is used for synthesis. Fatty acids will be stored if they are not needed to meet energy needs. The main storage site for fatty acids is adipose tissue. The storage stages are: Fat storage and reuse Fatty acids are transported from the liver as VLDL complexes. Fatty acids are then converted into triglycerides in adipose cells for storage. Glycerol 3-phosphate is required to make triglycerides. This must be available from glucose. As a result, we cannot store fat if there is no excess glucose inthe body. If energy needs cannot be met by carbohydrates, these triglyceride stores can be reused. Triglycerides will be broken down into glycerol and fatty acids.