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A significant proportion of the fatty acids in the body are obtained from the diet, in the form of triglycerides of either animal or plant origin. The fatty acids in the fats obtained from land animals tend to be saturated, whereas the fatty acids in the triglycerides of fish and plants are often polyunsaturated and therefore present as oils.
Ketones are needed as fatty acids cannot pass the blood-brain barrier, blood glucose levels are low and glycogen reserves depleted. Ketones also convert to acetyl-CoA faster than fatty acids. [15] [16] After the ketones convert to acetyl-CoA in a process known as ketolysis, it enters the citric acid cycle to produce ATP by oxidative ...
Lipids (oleaginous) are chiefly fatty acid esters, and are the basic building blocks of biological membranes. Another biological role is energy storage (e.g., triglycerides ). Most lipids consist of a polar or hydrophilic head (typically glycerol) and one to three non polar or hydrophobic fatty acid tails, and therefore they are amphiphilic .
Fatty acids exhibit reactions like other carboxylic acids, i.e. they undergo esterification and acid-base reactions. Fatty acids do not show a great variation in their acidities, as indicated by their respective pK a. Nonanoic acid, for example, has a pK a of 4.96, being only slightly weaker than acetic acid (4.76).
Fatty acid synthesis occurs in the cytoplasm of cells while oxidative degradation occurs in the mitochondria. Many of the enzymes for the fatty acid synthesis are organized into a multienzyme complex called fatty acid synthase. [5] The major sites of fatty acid synthesis are adipose tissue and the liver. [6]
Synthesis of saturated fatty acids via fatty acid synthase II in E. coli. Straight-chain fatty acid synthesis occurs via the six recurring reactions shown below, until the 16-carbon palmitic acid is produced. [2] [3] The diagrams presented show how fatty acids are synthesized in microorganisms and list the enzymes found in Escherichia coli. [2]
A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule. Glycogen (black granules) in spermatozoa of a flatworm; transmission electron microscopy, scale: 0.3 μm. Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, [2] fungi, and bacteria. [3]
These lipases cleave free fatty acids from their attachment to glycerol in the lipid droplet of the adipocyte. The free fatty acids and glycerol are then released into the blood. The activity of hormone sensitive lipase is regulated by the circulating hormones insulin , glucagon , norepinephrine , and epinephrine .