For example, palmitic acid, a saturated fatty acid , is derived from the palm tree. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts. Fatty acids may be saturated or unsaturated.
In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated. Saturated fatty acids are saturated with hydrogen.
In other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Stearic acid is an example of a saturated fatty acid Figure. When the hydrocarbon chain contains a double bond, the fatty acid is unsaturated. Oleic acid is an example of an unsaturated fatty acid Figure. Most unsaturated fats are liquid at room temperature.
We call these oils. If there is one double bond in the molecule, then it is a monounsaturated fat e. A fat may contain similar or different fatty acids attached to glycerol. Long straight fatty acids with single bonds generally pack tightly and are solid at room temperature. Animal fats with stearic acid and palmitic acid common in meat and the fat with butyric acid common in butter are examples of saturated fats.
Plants store fat or oil in many seeds and use them as a source of energy during seedling development. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Cis and trans indicate the configuration of the molecule around the double bond.
If hydrogens are present in the same plane, it is a cis fat. If the hydrogen atoms are on two different planes, it is a trans fat. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. Unsaturated fats help to lower blood cholesterol levels; whereas, saturated fats contribute to plaque formation in the arteries. The food industry artificially hydrogenates oils to make them semi-solid and of a consistency desirable for many processed food products.
Simply speaking, hydrogen gas is bubbled through oils to solidify them. During this hydrogenation process, double bonds of the cis — conformation in the hydrocarbon chain may convert to double bonds in the trans — conformation.
Margarine, some types of peanut butter, and shortening are examples of artificially hydrogenated trans fats. Many fast food restaurants have recently banned using trans fats, and food labels are required to display the trans fat content.
Essential fatty acids are those that the human body requires but does not synthesize. Consequently, they have to be supplemented through ingestion via the diet. Omega -3 fatty acids like those in Figure fall into this category and are one of only two known for humans the other is omega-6 fatty acid. Nutritionally important because the body does not make them, omega-3 fatty acids include alpha-linoleic acid ALA , eicosapentaenoic acid EPA , and docosahexaenoic acid DHA , all of which are polyunsaturated.
Salmon, trout, and tuna are good sources of omega-3 fatty acids. Research indicates that omega-3 fatty acids reduce the risk of sudden death from heart attacks, lower triglycerides in the blood, decrease blood pressure, and prevent thrombosis by inhibiting blood clotting.
They also reduce inflammation, and may help lower the risk of some cancers in animals. Like carbohydrates, fats have received considerable bad publicity. However, fats do have important functions. Many vitamins are fat soluble, and fats serve as a long-term storage form of fatty acids: a source of energy. They also provide insulation for the body. Long fatty acid chains esterified to long-chain alcohols comprise waxes. Like fats, they are comprised of fatty acid chains attached to a glycerol or sphingosine backbone.
A phosphate group alone attached to a diaglycerol does not qualify as a phospholipid. It is phosphatidate diacylglycerol 3-phosphate , the precursor of phospholipids. An alcohol modifies the phosphate group. Daniel M. A new study identifies a modified version of adipokine as a possible therapeutic intervention for Type 2 diabetes. In this technique, an enzyme is fused to a protein of interest and exogenously introduced into cells.
Blocking steroid hormone synthesis blocks cancer. Focusing on this phospholipid in both cellular models and a clinical trial has shown promise in improving the molecular and clinical effects of TAFAZZIN deficiency. These small green organelles and their relatives are involved in a broad range of other tasks, from manufacturing nutrients and signaling stress to fostering plant immunity.
Lipid News. By Daniel M. Raben and Richard Epand. Contribute your story. Related articles At the interface Lina M. Targeting cardiolipin modification in a genetic disorder Arianna F.
Journal News. Read More. Although they do not resemble the other lipids, they are grouped with them because they are also hydrophobic and insoluble in water. All steroids have four linked carbon rings, and many of them, like cholesterol, have a short tail. Many steroids also have the —OH functional group, and these steroids are classified as alcohols called sterols. Steroid Structures : Steroids, such as cholesterol and cortisol, are composed of four fused hydrocarbon rings.
Cholesterol is the most common steroid and is mainly synthesized in the liver; it is the precursor to vitamin D. Cholesterol is also a precursor to many important steroid hormones like estrogen, testosterone, and progesterone, which are secreted by the gonads and endocrine glands. Cholesterol also plays a role in synthesizing the steroid hormones aldosterone, which is used for osmoregulation, and cortisol, which plays a role in metabolism.
Cholesterol is also the precursor to bile salts, which help in the emulsification of fats and their absorption by cells. It is a component of the plasma membrane of animal cells and the phospholipid bilayer. Being the outermost structure in animal cells, the plasma membrane is responsible for the transport of materials and cellular recognition; and it is involved in cell-to-cell communication. Thus, steroids also play an important role in the structure and function of membranes. It has also been discovered that steroids can be active in the brain where they affect the nervous system, These neurosteroids alter electrical activity in the brain.
They can either activate or tone down receptors that communicate messages from neurotransmitters. Since these neurosteroids can tone down receptors and decrease brain activity, steroids are often used in anesthetic medicines. Privacy Policy. Skip to main content. Search for:. Lipids Lipid Molecules Fats and oils, which may be saturated or unsaturated, can be unhealthy but also serve important functions for plants and animals. Learning Objectives Differentiate between saturated and unsaturated fatty acids.
Key Takeaways Key Points Fats provide energy, insulation, and storage of fatty acids for many organisms. Fats may be saturated having single bonds or unsaturated having double bonds. Unsaturated fats may be cis hydrogens in same plane or trans hydrogens in two different planes. Olive oil, a monounsaturated fat, has a single double bond whereas canola oil, a polyunsaturated fat, has more than one double bond. Omega-3 fatty acid and omega-6 fatty acid are essential for human biological processes, but they must be ingested in the diet because they cannot be synthesized.
Key Terms hydrogenation : The chemical reaction of hydrogen with another substance, especially with an unsaturated organic compound, and usually under the influence of temperature, pressure and catalysts. It contains the functional group carbon-oxygen double bond joined via carbon to another oxygen atom.
OH ; characteristic of carboxylic acids. Phospholipids Phospholipids are amphipathic molecules that make up the bilayer of the plasma membrane and keep the membrane fluid. Learning Objectives Describe phospholipids and their role in cells. Key Takeaways Key Points Phospholipids consist of a glycerol molecule, two fatty acids, and a phosphate group that is modified by an alcohol. The phosphate group is the negatively-charged polar head, which is hydrophilic.
The fatty acid chains are the uncharged, nonpolar tails, which are hydrophobic. Since the tails are hydrophobic, they face the inside, away from the water and meet in the inner region of the membrane.
Since the heads are hydrophilic, they face outward and are attracted to the intracellular and extracellular fluid. If phospholipids are placed in water, they form into micelles, which are lipid molecules that arrange themselves in a spherical form in aqueous solutions.
Key Terms micelle : Lipid molecules that arrange themselves in a spherical form in aqueous solutions. Micelles : An example of micelles in water. Steroids Steroids, like cholesterol, play roles in reproduction, absorption, metabolism regulation, and brain activity. Learning Objectives Describe some functions of steroids.
Key Takeaways Key Points Steroids are lipids because they are hydrophobic and insoluble in water, but they do not resemble lipids since they have a structure composed of four fused rings. Cholesterol is the most common steroid and is the precursor to vitamin D, testosterone, estrogen, progesterone, aldosterone, cortisol, and bile salts.
0コメント