DISCUSS_LIPIDS_METABOLISM.docx

UNIVERSITY OF JUBA SCHOOL OF COMMUNITY STUDIES AND RURAL DEVELOPMENT DEPARTMENT OF COMMUNITY STUDIES \[FOOD & NUTRITION\] PROGRAM: DEGREE Course: FOOD BIOCHEMISTRY Topic: DISCUSS LIPIDS METABOLISM ACADEMIC YEAR: 2023-2024 4^TH^ YEAR SEMESTER SEVEN GROUP 'A' ASSIGNMENT G.A MEMBERS LIST +---...

UNIVERSITY OF JUBA SCHOOL OF COMMUNITY STUDIES AND RURAL DEVELOPMENT DEPARTMENT OF COMMUNITY STUDIES \[FOOD & NUTRITION\] PROGRAM: DEGREE Course: FOOD BIOCHEMISTRY Topic: DISCUSS LIPIDS METABOLISM ACADEMIC YEAR: 2023-2024 4^TH^ YEAR SEMESTER SEVEN GROUP 'A' ASSIGNMENT G.A MEMBERS LIST +-----------------------+-----------------------+-----------------------+ | S/NO | NAME | INDEX NO | +=======================+=======================+=======================+ | 1. | AJANG WAI AJANG | 19-CRD-209 | +-----------------------+-----------------------+-----------------------+ | 2. | AKECH ATOK AKECH | 19-CRD-210 | +-----------------------+-----------------------+-----------------------+ | 3. | ELIZA LOU PANTHER | 19-CRD-241 | +-----------------------+-----------------------+-----------------------+ | 4. | ELIZABETH NYANHIAL | 19-CRD-243 | | | SOLOMON | | +-----------------------+-----------------------+-----------------------+ | 5. | ELIZABETH YAR MARIAL | 19-CRD-244 | +-----------------------+-----------------------+-----------------------+ INSTRUCTOR'S NAME: LEMI SAMUEL SUBMISSION DATE: JULY 23^RD^, 2024 **DISCUSS LIPIDS METABOLISM** **Lipid metabolism**  Is the synthesis and degradation of [lipids](https://en.wikipedia.org/wiki/Lipid) in cells, involving the breakdown and storage of fats for energy and the synthesis of structural and functional lipids, such as those involved in the construction of [cell membranes](https://en.wikipedia.org/wiki/Cell_membrane). In animals, these fats are obtained from food and are synthesized by the [liver](https://en.wikipedia.org/wiki/Liver). Lipogenesis is the process of synthesizing these fats. The majority of lipids found in the human body from ingesting food are [triglycerides](https://en.wikipedia.org/wiki/Triglycerides) and [cholesterol](https://en.wikipedia.org/wiki/Cholesterol). Other types of lipids found in the body are [fatty acids](https://en.wikipedia.org/wiki/Fatty_acid) and [membrane lipids](https://en.wikipedia.org/wiki/Membrane_lipids). Lipid metabolism is often considered the [digestion](https://en.wikipedia.org/wiki/Digestion) and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. [Vertebrates](https://en.wikipedia.org/wiki/Vertebrates) (including humans) use both sources of fat to produce [energy](https://en.wikipedia.org/wiki/Energy) for organs such as the [heart](https://en.wikipedia.org/wiki/Heart) to function. Since lipids are [hydrophobic](https://en.wikipedia.org/wiki/Hydrophobic_effect) molecules, they need to be solubilized before their metabolism can begin. Lipid metabolism often begins with [hydrolysis](https://en.wikipedia.org/wiki/Hydrolysis), which occurs with the help of various enzymes in the digestive system. Lipid metabolism also occurs in plants, though the processes differ in some ways when compared to animals. The second step after the hydrolysis is the absorption of the fatty acids into the [epithelial cells](https://en.wikipedia.org/wiki/Epithelium) of the [intestinal wall](https://en.wikipedia.org/wiki/Gastrointestinal_wall). In the epithelial cells, fatty acids are packaged and transported to the rest of the body. Lipids Metabolic processes include; Lipid digestion, Lipid absorption, Lipid transportation, Lipid storage, Lipid catabolism, and Lipid biosynthesis. **Lipid catabolism** is accomplished by a process known as [beta oxidation](https://en.wikipedia.org/wiki/Beta_oxidation) which takes place in the [mitochondria](https://en.wikipedia.org/wiki/Mitochondria) and [peroxisome](https://en.wikipedia.org/wiki/Peroxisome) cell [organelles](https://en.wikipedia.org/wiki/Organelle). **Lipid digestion** [Digestion](https://en.wikipedia.org/wiki/Digestion) is the first step to lipid metabolism, and it is the process of breaking the triglycerides down into smaller [monoglyceride](https://en.wikipedia.org/wiki/Monoglyceride) units with the help of [lipase](https://en.wikipedia.org/wiki/Lipase) enzymes. Digestion of fats begin in the mouth through chemical digestion by [lingual lipase](https://en.wikipedia.org/wiki/Lingual_lipase). Ingested cholesterol is not broken down by the lipases and stays intact until it enters the epithelium cells of the small intestine. Lipids then continue to the stomach where chemical digestion continues by [gastric lipase](https://en.wikipedia.org/wiki/Gastric_lipase) and mechanical digestion begins ([peristalsis](https://en.wikipedia.org/wiki/Peristalsis)). The majority of lipid digestion and absorption, however, occurs once the fats reach the small intestines. Chemicals from the pancreas ([pancreatic lipase family](https://en.wikipedia.org/wiki/Pancreatic_lipase_family) and [bile salt-dependent lipase](https://en.wikipedia.org/wiki/Bile_salt-dependent_lipase)) are secreted into the small intestines to help breakdown the triglycerides, along with further mechanical digestion, until they are individual [fatty acid](https://en.wikipedia.org/wiki/Fatty_acid) units able to be absorbed into the small intestine\'s [epithelial cells](https://en.wikipedia.org/wiki/Epithelium). It is the pancreatic lipase that is responsible for signaling for the [hydrolysis](https://en.wikipedia.org/wiki/Hydrolysis) of the triglycerides into separate free fatty acids and glycerol units. **Lipid absorption** ***Flowchart showing the lipid absorption process*** The second step in lipid metabolism is absorption of fats. Short chain fatty acids can be absorbed in the [stomach](https://en.wikipedia.org/wiki/Stomach), while most absorption of fats occurs only in the [small intestines](https://en.wikipedia.org/wiki/Small_intestine). Once the triglycerides are broken down into individual fatty acids and glycerols, along with cholesterol, they will aggregate into structures called [micelles](https://en.wikipedia.org/wiki/Micelle). Fatty acids and monoglycerides leave the micelles and diffuse across the membrane to enter the intestinal epithelial cells. In the [cytosol](https://en.wikipedia.org/wiki/Cytosol) of epithelial cells, fatty acids and monoglycerides are recombined back into triglycerides. In the cytosol of epithelial cells, triglycerides and cholesterol are packaged into bigger particles called [chylomicrons](https://en.wikipedia.org/wiki/Chylomicron) which are [amphipathic](https://en.wikipedia.org/wiki/Amphipathic) structures that transport digested lipids. Chylomicrons will travel through the bloodstream to enter [adipose](https://en.wikipedia.org/wiki/Adipose) and other tissues in the body. **Lipid transportation** Due to the hydrophobic nature of [membrane lipids](https://en.wikipedia.org/wiki/Membrane_lipid), triglycerides and [cholesterols](https://en.wikipedia.org/wiki/Cholesterol), they require special transport proteins known as lipoproteins. The amphipathic structure of lipoproteins allows the triglycerides and cholesterol to be transported through the [blood](https://en.wikipedia.org/wiki/Blood). Chylomicrons are one sub-group of lipoproteins which carry the digested lipids from small intestine to the rest of the body. The varying densities between the types of lipoproteins are characteristic to what type of fats they transport. For example, very-low-density lipoproteins ([VLDL](https://en.wikipedia.org/wiki/VLDL)) carry the triglycerides synthesized by our body and [low-density lipoproteins](https://en.wikipedia.org/wiki/Low-density_lipoprotein) (LDL) transport cholesterol to our peripheral tissues.^[\[6\]](https://en.wikipedia.org/wiki/Lipid_metabolism#cite_note-Lehninger_2000-6)[\[1\]](https://en.wikipedia.org/wiki/Lipid_metabolism#cite_note-MM_Lipid_metabolism-1)^ A number of these lipoproteins are synthesized in the liver, but not all of them originate from this organ. **Lipid storage** Lipids are stored in [white adipose tissue](https://en.wikipedia.org/wiki/White_adipose_tissue) as triglycerides. In a lean young adult human, the mass of triglycerides stored represents about 10--20 kilograms. Triglycerides are formed from a backbone of glycerol with three fatty acids. Free fatty acids are activated into acyl-CoA and esterified to finally reach the triglyceride droplet. Lipoprotein lipase has an important role. **Lipid catabolism** Once the chylomicrons (or other lipoproteins) travel through the tissues, these particles will be broken down by [lipoprotein](https://en.wikipedia.org/wiki/Lipoprotein_lipase) lipase in the luminal surface of [endothelial cells](https://en.wikipedia.org/wiki/Endothelium) in [capillaries](https://en.wikipedia.org/wiki/Capillaries) to release triglycerides. Triglycerides will get broken down into fatty acids and glycerol before entering cells and remaining cholesterol will again travel through the blood to the liver.[^\[15\]^](https://en.wikipedia.org/wiki/Lipid_metabolism#cite_note-lipidlibrary.aocs.org-15) In the cytosol of the cell (for example a muscle cell), the [glycerol](https://en.wikipedia.org/wiki/Glycerol) will be converted to [glyceraldehyde 3-phosphate](https://en.wikipedia.org/wiki/Glyceraldehyde_3-phosphate), which is an intermediate in the [glycolysis](https://en.wikipedia.org/wiki/Glycolysis), to get further oxidized and produce energy. However, the main steps of fatty acids [catabolism](https://en.wikipedia.org/wiki/Catabolism) occur in the [mitochondria](https://en.wikipedia.org/wiki/Mitochondrion). Long chain fatty acids (more than 14 carbon) need to be converted to [fatty acyl-CoA](https://en.wikipedia.org/wiki/Fatty_acyl-CoA_esters) in order to pass across the mitochondria [membrane](https://en.wikipedia.org/wiki/Membrane).[^\[6\]^](https://en.wikipedia.org/wiki/Lipid_metabolism#cite_note-Lehninger_2000-6) [Fatty acid catabolism](https://en.wikipedia.org/wiki/Fatty_acid_metabolism) begins in the cytoplasm of [cells](https://en.wikipedia.org/wiki/Epithelial_cell) as [acyl-CoA synthetase](https://en.wikipedia.org/wiki/Acyl-CoA_synthetase) uses the energy from cleavage of an ATP to catalyze the addition of [coenzyme A](https://en.wikipedia.org/wiki/Coenzyme_A) to the fatty acid. The resulting [acyl-CoA](https://en.wikipedia.org/wiki/Acyl-CoA) cross the mitochondria membrane and enter the process of [beta oxidation](https://en.wikipedia.org/wiki/Beta_oxidation). The main products of the beta oxidation pathway are [acetyl-CoA](https://en.wikipedia.org/wiki/Acetyl-CoA) (which is used in the [citric acid cycle](https://en.wikipedia.org/wiki/Citric_acid_cycle) to produce energy), NADH and FADH. The process of beta oxidation requires the following enzymes: [acyl-CoA dehydrogenase](https://en.wikipedia.org/wiki/Acyl-CoA_dehydrogenase), [enoyl-CoA hydratase](https://en.wikipedia.org/wiki/Enoyl-CoA_hydratase), [3-hydroxyacyl-CoA dehydrogenase](https://en.wikipedia.org/wiki/3-hydroxyacyl-CoA_dehydrogenase), and [3-ketoacyl-CoA thiolase](https://en.wikipedia.org/wiki/3-ketoacyl-CoA_thiolase). The diagram to the left shows how fatty acids are converted into acetyl-CoA. The overall net reaction, using [palmitoyl-CoA](https://en.wikipedia.org/wiki/Palmitoyl-CoA) (16:0) as a model substrate is: - - - - - - - - - - - - - - - - - - - - 1. 2. 3. 4. 5. 6. 7. 8.