What Are Phospholipids

The fatty acids that are most common in phosphatidic acids are palmitic and stearic acids (both fully saturated) and oleic acid (with one double bond in the hydrocarbon chain). Further esterification of a phosphatidic acid with a low-molecular-weight alcohol gives a phospholipid. Several of the most common alcohols found in phospholipids are given in Table 19.3. 

Effects of optical bleaches [above) ordinary light [belov /) black light. 

Phospholipid A lipid containing glycerol esterified with two molecules of fatty acid and one molecule of phosphoric acid. 

TABLE 19. Low-Molecular-Weight Alcohols Most Common to Phospholipids 

Lipid bilayer A back-to-back arrangement of phospholipid monolayers. 

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What are phospholipids and glycolipids What properties do ey Ixave in common ... 

Several amino acids are broken down by de-carbo qflation. This reaction gives rise to what are known as biogenic amines, which have various functions. Some of them are components of biomolecules, such as ethanolamine in phospholipids (see p. 50). Cysteamine and T-alanine are components of coenzyme A (see p.l2) and of pantetheine (see pp. 108, 168). Other amines function as signaling substances. An important neurotransmitter derived from glutamate is y-aminobutyrate (GABA, see p.356). The transmitter dopamine is also a precursor for the catecholamines epinephrine and norepinephrine (see p.352). The biogenic amine serotonin, a substance that has many effects, is synthesized from tryptophan via the intermediate 5-hydroxytryptophan. 

What are the implications of these studies of n-3 fatty acid deficiency and subsequent repletion in rhesus monkeys to human beings 1 i rst. these data strongly suggest that any n-3 fatty acid-deficient state will be corrected by fish oil containing EPA and DHA or in other studies, a diet containing n-3 fatty acids from soy oil (18 3n-3 linolenic acid). The brain phospholipids will readily assemble the correct amounts of DHA in the sn-2 position of the phospholipid molecular species, furthermore, other fatty acids of the n-6 series, which occupy that position in the deficient state, will ultimately be removed and replaced by DHA. It is not certain yet if functional abnormalities would likewise be corrected because the appropriate function may need to take place at a certain stage of development or it may not occur at all or to a lesser degree when there has been biochemical correction. 

The intercellular movement of phospholipids and cholesterol is mediated by various proteins. What are the two major mechanisms by which lipids are exported from cells ... 

What are the structural differences between triglycerides (triacylglycerols) and phospholipids ... 

Low-density lipoproteins are the migor carriers of cholesterol in the blood. They consist of a core of cholesterol ester molecnles surrounded by a coat of phospholipid molecules, which in turn is wrapped in a single apolipoprotein. Blood also contains what are called chylomicrons. These have a very low phospholipid content and consist mainly of a core of triglycerides coated with a thin layer of protein. 

Over 40 years since it what found that phospholipids can form closed bilayered structures in aqueous systems, liposomes have made a long way to become a popular pharmaceutical carrier for numerous practical applications. Liposomes are phospholipid vesicles, produced by various methods from lipid dispersions in water. Liposome preparation, their physicochemical properties and possible biomedical application have already been discussed in several monographs. Many different methods exist to prepare liposomes of different sizes, structure and size distribution. The most frequently used methods include ultrasonication, reverse phase evaporation and detergent removal from mixed lipid-detergent micelles by dialysis or gel-filtration. To increase liposome stability towards the physiological environment, cholesterol is incorporated into the liposomal membrane (up to 50% mol). The size of liposomes depends on their composition and preparation method and can vary from... 

What are the main functions of phospholipids and glycolipids in the body ... 

Is not everybody worried about cholesterol And cholesterol is a steroid. Well then, are not steroids bad What are steroids, anyway Chemically, they belong to a group of compounds called lipid. Lipid is a fancy (collective) term for oil-soluble compounds and includes fats, phospholipids, and steroids. Fats are chanically long chain fatty acids and almost like wax. Phospholipids are combination of fatty acids and glycerine with some special groups on top and make up the membrane of cells (Fig. 1.5). By the way, cholesterol also makes up an essential part of cell manbranes along with phospholipids. Cholesterol is indeed a necessity. Only excess presence of cholesterol is a health hazard. 

Two conditions in which the rate of ketone body formation is increased are hypoglycaemia and prolonged starvation in adults or short-term starvation in children. What is the mechanism for increasing the rate Although there are several fates for fatty acids in the liver, triacylglycerol, phospholipid and cholesterol formation and oxidation via the Krebs cycle, the dominant pathway is ketone body formation (Figure 7.20). Three factor regulate the rate of ketone body formation (i) hormone sensitive lipase activ-... 

A more interesting problem from both the experimental and theoretical point of view is the lateral diffusion of phospholipids in mixtures of lipids, when both solid and fluid phases coexist. At least three questions arise in connection with this problem. (1) What is the rate of lateral diffusion of phospholipids in solid solution domains (2) To what extent do solid solution domains act as obstacles to the lateral diffusion of lipid molecules in fluid domains (3) To what extent are there composition and density fluctuations present in fluid lipid bilayers, and to what extent do these fluctuations affect lateral diffusion Let us consider these questions one at a time, bearing in mind that these questions may to some extent be interrelated. 

I am curious to know by what mechanism simple phospholipids, such as liposomes or vesicles, are instantly recognized by within blood as non-... 

Synaptic vesicles can be isolated in large quantities. Their composition is well known, and the proteins have been studied intensively. Indeed, much of what we know about exocytosis and vescular transport has been learned from investigation of synaptic vesicles.554 561 562 A small synaptic vesicle of 35 nm diameter will contain -10,000 phospholipid molecules in its membrane and only about 200 protein molecules, at least one of which must be a 13-subunit vacuolar type proton pump (Fig. 18-14). This pump acidifies the vacuole, allowing uptake of a neurotransmitter. Although many different proteins may be found in synaptic membranes, only about 15, which are listed in Table 30-6, are found in all synaptic vesicles and appear essential to function. 

What physical properties are conferred on biological membranes by phospholipids How can the charge characteristics of the phospholipids affect binding of peripheral proteins to the membrane What role... 

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