Structure And Functions Of Lipids Pdf


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Lipids comprise a group of compounds such as fats, oils, steroids and waxes found in living organisms.

Lipids are a group of biological molecules that include fats, oils and some steroids.

In biology and biochemistry , a lipid is a macro biomolecule that is soluble in nonpolar solvents. The functions of lipids include storing energy, signaling , and acting as structural components of cell membranes. Biological lipids originate entirely or in part from two distinct types of biochemical subunits or "building-blocks": ketoacyl and isoprene groups. Although the term "lipid" is sometimes used as a synonym for fats , fats are a subgroup of lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives including tri- , di- , monoglycerides , and phospholipids , as well as other sterol -containing metabolites such as cholesterol.

2.8: Structure and Function - Lipids and Membranes

Lipids comprise a group of compounds such as fats, oils, steroids and waxes found in living organisms. Both prokaryotes and eukaryotes possess lipids, which play many important roles biologically, such as membrane formation, protection, insulation, energy storage, cell division and more. In medicine, lipids refer to blood fats. Lipids designate fats, oils, steroids and waxes found in living organisms.

Lipids serve multiple functions across species, for energy storage, protection, insulation, cell division and other important biological roles. Lipids are made of a triglyceride that is made from the alcohol glycerol, plus fatty acids.

Additions to this basic structure yield great diversity in lipids. Over 10, kinds of lipids have been discovered so far, and many work with a huge diversity of proteins for cellular metabolism and material transport. Lipids are considerably smaller than proteins. Fatty acids are one type of lipid and serve as building blocks for other lipids as well. Fatty acids contain carboxyl -COOH groups bound to a carbon chain with attached hydrogens. This chain is water-insoluble. Fatty acids can be saturated or unsaturated.

Saturated fatty acids have single carbon bonds, whereas unsaturated fatty acids have double carbon bonds. When saturated fatty acids combine with triglycerides, this results in solid fats at room temperature. This is because their structure causes them to pack together tightly.

In contrast, unsaturated fatty acids combined with triglycerides tend to yield liquid oils. The kinked structure of unsaturated fats yields a looser, more fluid substance at room temperature. Phospholipids are made of a triglyceride with a phosphate group substituted in for a fatty acid.

They can be described as having a charged head and hydrocarbon tail. Their heads are hydrophilic, or water-loving, whereas their tails are hydrophobic or repellant to water. Another example of a lipid is cholesterol. Cholesterols arrange into rigid ring structures of five or six carbon atoms, with hydrogens attached and a flexible hydrocarbon tail. The first ring contains a hydroxyl group that extends into water environments of animal cell membranes.

The rest of the molecule, however, is water insoluble. Polyunsaturated fatty acids PUFAs are lipids that aid in membrane fluidity. PUFAs participate in cell signaling related to neural inflammation and energetic metabolism. They can provide neuroprotective effects as omega-3 fatty acids, and in this formulation, they are anti-inflammatory. For omega-6 fatty acids, PUFAs can cause inflammation.

Sterols are lipids found in plant membranes. Glycolipids are lipids linked to carbohydrates and are part of cellular lipid pools. Lipids play several roles in organisms.

Lipids make up protective barriers. They comprise cell membranes and some of the structure of cell walls in plants. Lipids provide energy storage to plants and animals. Quite often, lipids function alongside proteins. Lipid functions can be affected by changes to their polar head groups as well as by their side chains. Phospholipids form the foundation for lipid bilayers, with their amphipathic nature, that make up cell membranes. The outer layer interacts with water while the inner layer exists as a flexible oily substance.

The liquid nature of cell membranes aids in their function. Lipids make up not only plasma membranes, but also cellular compartments such as the nuclear envelope, endoplasmic reticulum ER , Golgi apparatus and vesicles. Lipids also participate in cell division. Dividing cells regulate lipid content depending on the cell cycle. At least 11 lipids are involved in cell cycle activity. Sphingolipids play a role in cytokinesis during interphase. Because cell division results in plasma membrane tension, lipids appear to help with mechanical aspects of division such as membrane stiffness.

Lipids provide protective barriers for specialized tissues such as nerves. The protective myelin sheath surrounding nerves contains lipids. Lipids provide the greatest amount of energy from consumption, having more than twice the amount of energy as proteins and carbohydrates. The body breaks down fats in digestion, some for immediate energy needs and others for storage.

The body draws upon the lipid storage for exercise by using lipases to break down those lipids, and eventually to make more adenosine triphosphate ATP to power cells. In plants, seed oils such as triacylglycerols TAGs provide food storage for seed germination and growth in both angiosperms and gymnosperms. These oils are stored in oil bodies OBs and protected by phospholipids and proteins called oleosins. All of these substances are produced by the endoplasmic reticulum ER.

The oil body buds from the ER. Lipids give plants the necessary energy for their metabolic processes and signals between cells. The phloem, one of the chief transport portions of plants along with the xylem , contains lipids such as cholesterol, sitosterol, camposterol, stigmasterol and several varying lipophilic hormones and molecules. The various lipids may play a role in signaling when a plant is damaged. Phospholipids in plants also work in response to environmental stressors on the plants as well as in response to pathogen infections.

In animals, lipids also serve as insulation from the environment and as protection for vital organs. Lipids provide buoyancy and waterproofing as well. Lipids called ceramides, which are sphingoid-based, perform important functions for skin health.

They help form the epidermis, which serves as the outermost skin layer that protects from the environment and prevents water loss. Ceramides work as precursors for sphingolipid metabolism; active lipid metabolism occurs within the skin.

Sphingolipids make up structural and signaling lipids found in the skin. Sphingomyelins, made from ceramides, are prevalent in the nervous system and help motor neurons survive. Lipids also play a role in cell signaling. In the central and peripheral nervous systems, lipids control fluidity of membranes and aid in electrical signal transmissions. Lipids help stabilize synapses.

Lipids are essential for growth, a healthy immune system and reproduction. Lipids allow the body to store vitamins in the liver such as the fat-soluble vitamins A, D, E and K. Cholesterol serves as a precursor for hormones such as estrogen and testosterone. It also makes bile acids, which dissolve fat. The liver and intestines make approximately 80 percent of cholesterol, whereas the rest is obtained from food.

Generally, animal fats are saturated and therefore solid, whereas plant oils tend to be unsaturated and therefore liquid. Animals cannot produce unsaturated fats, so those fats must be consumed from producers such as plants and algae. In turn, animals that eat those plant consumers such as cold-water fish gain those beneficial fats.

Unsaturated fats are the healthiest fats to eat as they decrease the risk of diseases. Examples of these fats include oils such as olive and sunflower oils, as well as seeds, nuts and fish.

Leafy green vegetables are also good sources of dietary unsaturated fats. The fatty acids in leaves are used in chloroplasts. Trans-fats are partially hydrogenated plan oils that resemble saturated fats. Previously used in cooking, trans-fats are now considered unhealthy for consumption. Saturated fats should be consumed less than unsaturated fats as saturated fats may increase disease risk.

Examples of saturated fats include red animal meat and fatty dairy products as well as coconut oil and palm oil. When medical professionals refer to lipids as blood fats, this describes the kind of fats often discussed regarding cardiovascular health, particularly cholesterol.

Lipoproteins aid in the transport of cholesterol though the body. It serves to help remove bad cholesterol via the liver. Bad fats increase heart attack and stroke risk due to their accumulation as plaque, which can lead to clogged arteries. Therefore a balance of lipids is crucial to health. Inflammatory skin conditions may benefit from the consumption of certain lipids such as eicosapentaenoic acid EPA and docsahexaenoic acid DHA.

A number of diseases are related to lipids in the human body. Hypertriglyceridemia, a condition of high triglycerides in the blood, can lead to pancreatitis.

A number of medicines work to reduce triglycerides, such as by enzymes that degrade blood fats. High triglyceride reduction has also been found in some individuals by medical supplementation via fish oil. Hypercholesterolemia high blood cholesterol can be acquired or genetic. Individuals with familial hypercholesterolemia possess extraordinarily high cholesterol values that cannot be controlled via medication.

This greatly increases the risk of heart attack and stroke, with many individuals dying before reaching 50 years of age. Genetic diseases that result in high lipid accumulation on blood vessels are referred to as lipid storage diseases.

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Figure 1. Hydrophobic lipids in the fur of aquatic mammals, such as this river otter, protect them from the elements. Lipids include a diverse group of compounds that are largely nonpolar in nature. This is because they are hydrocarbons that include mostly nonpolar carbon—carbon or carbon—hydrogen bonds. Lipids perform many different functions in a cell.

The excess energy from the food we eat is digested and incorporated into adipose tissue, or fatty tissue. Most of the energy required by the human body is provided by carbohydrates and lipids. As discussed in the Carbohydrates chapter, glucose is stored in the body as glycogen. While glycogen provides a ready source of energy, lipids primarily function as an energy reserve. As you may recall, glycogen is quite bulky with heavy water content, thus the body cannot store too much for long. Alternatively, fats are packed together tightly without water and store far greater amounts of energy in a reduced space.

Lipid , any of a diverse group of organic compounds including fats , oils , hormones , and certain components of membranes that are grouped together because they do not interact appreciably with water. One type of lipid, the triglycerides , is sequestered as fat in adipose cells , which serve as the energy-storage depot for organisms and also provide thermal insulation. Some lipids such as steroid hormones serve as chemical messengers between cells , tissues , and organs , and others communicate signals between biochemical systems within a single cell. The membranes of cells and organelles structures within cells are microscopically thin structures formed from two layers of phospholipid molecules. Membranes function to separate individual cells from their environments and to compartmentalize the cell interior into structures that carry out special functions. So important is this compartmentalizing function that membranes, and the lipids that form them, must have been essential to the origin of life itself. A lipid is any of various organic compounds that are insoluble in water.


cholesterol, lipid oxidation and antioxidants; COX activity & COX-1 and COX-2 inhibitors. • The chemistry of lipids is all about how structure affects function. This.


Lipids: Definition, Structure, Function & Examples

Unlike other biomolecule groups, lipids are not defined by the presence of specific structural characteristics. Lipids are insoluble biomolecules, defined by an overall lack of polarity necessary for solubility in water-based solutions. In popular culture, fats are synonymous with lipids, giving lipids a negative role in diet and health. However, lipids play vital roles in many cellular processes including energy storage, structural support, protection, and communication. Common lipid groups include waxes, steroids, fats, and phospholipids.

The Functions of Lipids in the Body

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Lipids Structure & Functions

Lipids are a diverse group of molecules that all share the characteristic that at least a portion of them is hydrophobic. Other, amphipathic lipids, such as glycerophospholipids and sphingolipids spontaneously organize themselves into lipid bilayers when placed in water. Interestingly, major parts of many lipids can be derived from acetyl-CoA. Figure 2.

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Lipids. Benjamin Caballero, MD, PhD. Johns Hopkins University Fatty Acids—​Basic building blocks for fats Cell membrane structure, myelination. ▫ Signal.


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