What Are Steroids

The venoms of certain snakes contain enzymes called phospholipases that catalyze the hydrolysis of carboxylic ester bonds of phospholipids. The venom of the eastern diamondback rattlesnake (Crotalus adaman-teus) and that of the Indian cobra (Naja naja) both 

Indian cobras kill several thousand people each year. 

Unsaturated hydrocarbon chains, by contrast, have one or more cis double bonds, which cause kinks in the chains, so they pack neither as closely nor as orderly as saturated chains. The disordered packing of unsaturated hydrocarbon chains leads to fluidity of the bUayer. 

Biological membranes are made of lipid bUayers. The most satisfactory model for the arrangement of phospholipids, proteins, and cholesterol in plant and animal membranes is the fluid-mosaic model proposed in 1972 by S. J. Singer and G. Nicolson. The term mosaic signifies that the various components in the membrane coexist side by side, as discrete units, rather than combining to form new molecules or ions. Fluid signifies that the same sort of fluidity exists in membranes that we have already seen in lipid bilayers. Furthermore, the protein components of membranes float in the bilayer and can move laterally along the plane of the membrane. 

A model of a biological membrane consisting of a phospholipid bilayer, with proteins, carbohydrates, and other lipids embedded in, and on the surface of, the bilayer. 

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At the Seoul Olympics 1988 the Canadian athlete Ben Johnson was stripped of his gold medal and the title of the fastest runner ever for taking a banned substance, an anabolic steroid. So what are steroids and why are they banned from athletics ... 

What are steroids Steroids have a characteristic fused-ring structure. Other lipids are open-chain compounds. 

What are steroids What are some of the fxmctions of steroids 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. 

You have surely come across the items of news that appear quite frequently in the media, related to world-class athletes and sports personalities abusing anabolic steroids, e.g. nandrolone, to enhance performance and also to improve physical appearance. What are these substances Well, all these drugs and many other important drugs belong to the class of compounds called steroids. 

Kastner, P., Mark, M., Chambon, P. (1995). Non-steroid nuclear receptors what are genetic studies telling us about their role in real life Cell 83,859-869. 

What do steroids have to do with hydrocarbons Steroids are unsaturated compounds. Although they are complex organic molecules, their basic structure centres on four rings of carbon atoms. In other words, steroids are built around ring structures of alkanes and alkenes. 

What are the advantages of NSAID(s) over the steroidal drugs used as anti-inflammatoiy drugs Support your answer with the suitable examples. 

Reflect and Apply What structural feature do all steroids have in common What are the biosynthetic implications of this common feature ... 

What is a hormone What are the two major categories of steroid hormones ... 

Well, you have to go back to what some steroids are responsible for, notably testosterone (see p489). It is responsible for the development of male sexual characteristics and also has anabolic effects, building tissue and muscle. After World War II, some athletes started to take it to get an unfair competitive edge . The practice seems to have started with Russian weightlifters and was rapidly taken up by US athletes. 

What are the similarities and differences between the steroid hormones estradiol and testosterone ... 

Substituent groups on the steroid ring system can be either axial or equatorial. As with simple cyclohexanes (Section 4.7), equatorial substitution is generally more favorable than axial substitution for steric reasons. The hydroxyl group at C3 of cholesterol, for example, has the more stable equatorial orientation. Unlike what happens with simple cyclohexanes, however, steroids are rigid molecules whose geometry prevents cyclohexane ring-flips. 

In the preceding chapters, the synaptic pharmacology of those substances clearly established as NTs in the CNS, i.e. glutamate, GABA, ACh, NA, DA, 5-HT and certain peptides, has been discussed in some detail. There are other substances found in the CNS that could have a minor transmitter role, e.g. ATP, histamine and adrenaline, while still others that cannot claim such a property but clearly modify CNS function in some way, e.g. steroids, prostaglandins and nitric oxide. We will consider each of them in what we hope is appropriate detail. 

The signal is what starts everything off. Signals take a variety of forms, but for our purposes there are only two. The first type are signals that go into the cell, bind to internal receptors, and exert their effects. Steroid hormones, vitamin D, thyroid hormone, and retinoids are the only members of this class. All of the intracellular receptors ultimately activate the transcription of regulated genes. The common feature of signals that enter the cell is that they are all small lipophilic molecules that can cross the cell membrane. 

Clinical tests are targeted to measure the concentration of different sets of compounds, such as small molecules (e.g., amino acids, fatty acids, organic acids, steroids) and peptides and proteins (e.g., thyroid stimulating hormone, hemoglobin A 1C) and oligonucleotides (e.g., DNA, RNA, SNPs). The presence, absence, or altered concentrations of a diagnostic compound or compounds may indicate the presence of a disease, type and severity of a disease, risk factors for disease, what is the basis for... 

Specific transcription factors bind to enhancer regions or, in a few cases, to silencers and mod-ciate the formation of the initiation complex, thus regulating the rate of initiation of transcription. Each gene contains a variety of enhancer or silencer sequences in its regulatory region. The exact combination of specific transcription factors available (and active) in a particular cell at a particular time determines which genes will be transcribed at what rates, because specific transcription factors are proteins, their expression can be cell-type specific.. Additionally, hormones may regulate the activity of some specific transcription factors. Examples include steroid receptors and the CREB protein. 

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