Structural Biochemistry/Lipid Droplets and Cellular Lipid Metabolism

From Wikibooks, open books for an open world
< Structural Biochemistry
Jump to: navigation, search

No one cares about your garage band.

Properties of Lipid Droplets[edit]

1. Almost every cell has lipid droplets or has the capacity to produce them

2. Some bacteria use lipid droplets to store lipids themselves

3. Lipid droplets' abundance varies greatly in cells.

4. Lipid droplets' size also varies greatly depending on cell types. Many cells are known to contain small LDs (100-200 nm). On the other hand, in white adipocytes, for instance, have diameters up to 100 micrometers, occupying most of the cytoplasm.

Functions of Lipid Droplets[edit]

1. Generally they are intracellular lipid reservoirs that become useful as they provide building blocks for cell membranes or substrates for energy metabolism[1]

2. Lipid droplets may be used as places for synthesizing some lipids. For instance, TGs are produced in the Er and lipid droplets.

3. Lipids droplets may be used to store some proteins.

4. Lipid droplets are involved in hepatitis C virus assembly [2]

Lipid Droplets and Tissues[edit]

Adipose Tissue In mammals and birds, adipose tissues is located in specific areas in the body and are regulated by hormones. They are more prominently used as insulation for endotherms. There are two types of adipocytes: white adipocytes and brown adipocytes. Adipocytes are the cells that are utilized by the body to store lipids in lipid droplets. White adipocytes store lipids in a single large lipid droplet in the cytoplasm. They are also known to store cholesterol esters and fat-soluble vitamins. The white adipocytes utilize leptin to regulate the lipid storage. Brown adipocytes catabolize lipids in order to generate heat. They store lipids in smaller and more numerous lipid droplets in the cytoplasm.

Liver The liver has the second greatest lipid in LD form storage capacity. They store the lipid droplets in hepatocytes. In humans, a high amount of lipid droplets can lead to an illness called fatty liver.

Small Intestine The small intestine is where a majority of nutrient absorption occurs. By utilizing its microvilli, the small intestine is able to absorb 95% of a meal's fat content. The lipid droplets are stored in intestinal enterocytes. The enterocytes have a large surface area and are able to store and synthesize triacylglycerols(TGs).

Yolk Sac The yolk sac stores lipids in a similar manner to intestinal enterocytes and liver hepatocytes. They are able to store lipid droplets and export via apoB-containing lipoproteins.

Skeletal Muscle Muscle is not known to be a large lipid storage unit. When humans store lipids in their skeletal muscles it is usually a side effect of obesity because of insulin resistance. There is an exception with this in highly-trained athletes. Athletes use a high volume of ATP when they are training so the body needed a way to keep a lipid reserve for when the muscles need more energy. This compensation occurs with the lipid droplets being stored in skeletal muscle cells near the mitochondria. This is considered the athelete's paradox because lipid droplet storage in skeletal muscles is usually a bad sign.

Adrenal Cortex The adrenal cortex is able to store large amounts of sterol esters(SEs). The SEs are most likely stored in the form of cholesterols for steroid hormone synthesis. Also the yellow coloring of the tissue can be credited to the lipids.2

Reference[edit]

1. Nature.com. Nature Publishing Group, n.d. Web. 07 Dec. 2012.

2. http://www.ncbi.nlm.nih.gov/pubmed/22524315

  1. “Lipid Droplets and Cellular Lipid Metabolism” Annual Review of Biochemistry Vol 81 587-714, by Tobias C. Walther and Robert V. Farese Jr
  2. “Lipid Droplets and Cellular Lipid Metabolism” Annual Review of Biochemistry Vol 81 587-714, by Tobias C. Walther and Robert V. Farese Jr