what do you think functions of the nictitating membrane,and why?
598299
the nictitating memebrane is considered to the one of the vestigeal organ,in the body.Its mail function is to produce tears to clean the membrane on the eys when dust is accumulated on it.
124857
This lacks an actual question, but I see what your teacher is aiming at. \nHint: what is the main function of the large intestin? What is reabsorbed there that you wouldn't especially need in aquatic environments?
518652
It is the simplest form of a cell membrane. Actually the cell on contain es the cell membrane and nothing else. It is used for research when doing tests on a cell membrane. It has nothing that could interfere with normals.
410297
Within a sponge, there is an intriguing body structure. While the sponge functions as a unified organism, each cell is a division of its own mini-organism. Essentially, a sponge is a combination of billions of cells that function together. Within the body of the sponge, several processes occur which are vital to its welfare. Most importantly, sponges conduct the processes of respiration, digestion, protection, development, and reproduction. \n\nAll of these processes are generated by the consistent filtration of the water encompassing it. Through an intricate system of incurrent and afferent ducts, it processes food, oxygen, and other useful materials. The exterior layer of skin is covered in pinacocytes, which open the afferent ducts. In addition, the afferent ducts allow water to be transferred through the porocytes. The functions of the afferent ducts are regulated by the myocytes, muscular cells that permit them to open and close. After this the water travels through the incurrent ducts. \n\nWithin the system of incurrent ducts, water is processed for useful materials. The interior layer of tissue forces the water through the ostioles into chambers lined with choanae and flagellates. Eventually, water is directed towards the atrial cavity. After the water is processed through the atrial cavity and removed of a sufficient amount of oxygen, it is released through the osculum. The osculum is a relatively maximized opening in the body of the sponge. At this point in filtration, waste water will be ejected.
597123
The Development of a Scientific Fact \n\nThe fluid-mosaic membrane model as a scientific fact \nWhat the model says \n\nThe fluid mosaic model of a biological membrane defines a phospholipid bilayer mixed with (integral) membrane proteins. The lipid bilayer, therefore, is not a continuous layer, but contains non-lipid molecules, in particular proteins. \n\nThe significance of the model \n\nThe fluid mosaic model is the only accepted proper description of a biological membrane. Its publication in 1972 by Singer and Nicolson (Science 1972 Feb. 18 175:23 720-31) put an end to other existing and competing models of biological membranes. These competing models assumed triple layers, with a lipid core layer and two protein layers, one on each side, but the proteins would not penetrate the lipid core, i.e., did not span the membrane. The fluid mosaic model, based on thermodynamic and functional considerations, postulated instead that proteins as the active components of signal transduction and transport,  must and can span the entire thickness of a lipid bilayer. Protein-lipid interaction was thought to be stabilized through hydrophobic (fat soluble) contact points on the surface of the proteins.  \n\nToday, the fluid-mosaic model is the only accepted model of the structure of biological membranes, including those of animals, plants, and microorganisms (see figure above for membranes of the cell wall of the bacteria Escherichia coli). the use of the same structure among all living organisms is consistent with the idea of a common ancestor organism (or organisms) from which all modern life forms have evolved. Since 1972 no modifications of the model have been necessary, also individual membranes differ in molecular composition, lipid types, or lipid to protein ratios.  \n\nTo understand the stability and form of membranes one needs to understand that they are solely determined by the aggregation behavior of phospholipids. These lipid types in effect form extensive, planar bimolecular films separating two aqueous compartments.  \n\n \n\nThe hydrophobic core of such a thin film functions as an electrical insulator (D=2; D stands for dielectric constant; a value of 2 represents hydrophobic environment, a value of 80 water) allowing diffusion of small hydrophobic solutes across membranes, but inhibits the diffusion of charged and hydrophilic, i.e., water soluble molecules. The incorporation of protein into these bimolecular films provides the necessary pathways for all charged and hydrophilic molecules. Cells have thus complete control over their membrane permeability because they can control protein function, but not the diffusion of small hydrophobic molecules across membranes. Cell membranes are thus clearly specific and selective.  \n\nTo understand the current model of biological membranes, one has to know the history of the study of cell membranes, both from a structural and functional point of view.  \n\n\nEarly developments \n\nThe first experimental indications for a bilayer structure have been obtained by measuring the size of a water surface that can be covered by phospholipids extracted from red blood cells. This area was about twice as large as the total surface area of red blood cells used to extract lipids. It turned out this first calculation was a lucky shot and with more accurate measurement, the two surface ratios would not have been 2:1 due to the presence of membrane proteins. This original finding, although not reproducible, stimulated membrane research and guided it into the right direction.  \n\nNeurobiologist started to characterize the function of neuronal cells by measuring action potentials which are the result of electrical currents flowing across cell membranes (called excitable membranes of nerve and muscle cells). Macroscopic current recordings of isolated nerve cells in the 1940s allowed the prediction of underlying molecular units called ion channels (the electric charges are carried by ions, charged atom
941524
Gee...broad question...depends what ur transporting.\ne.g. for gases u need a semi-permeable membrane, a thin membrane, a gradient, a moist/mucus surface
772768
It cushions the heart and regulates temperature. It also protects the heart from damage.
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http://en.wikipedia.org/wiki/Biological_membrane\n\nhttp://simscience.org/membranes/advanced/essay/biological_membranes1.html\n\nhttp://web.mit.edu/esgbio/www/cb/membranes/structure.html\n\nhttp://www.sci.uidaho.edu/bionet/biol115/t2_basics_of_life/lesson03/lesson3_mod1.htm\n\nhttp://www.chemsoc.org/ExemplarChem/entries/2002/Tim_Smith/membrane/index.html\n\nhttp://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=stryer.section.1629\n\nhttp://www.csupomona.edu/~dfhoyt/classes/zoo138/BIOL_MEMB.HTML\n\nhttp://www.studyworld.com/newsite/reportessay/Science/Biological%5CComponents_of_Biological_Membranes-384178.htm\n\nis that enough? :-)
778955
The cell membrane is a lipid bilayer made from phospholipids.  As a lipid, it is permeable to other lipids (e.g. steroid hormones) but not to polar molecules (e.g. potassium or glucose).  Polar molecules require various types of membrane proteins (e.g. potassium channels) or endocytosis (glucose) for absorption into the cell.  \n\nHope this is helpful for you.  Best wishes and good luck.
86313
Each cell is like a plastic bag filled with a spaghetti soup of all the different cell components. But it's a very special plastic bag, because it is permeable - water and friendly chemicals can pass through it, but bad guys get shut out. Rather like the firewall works (or should work!) when you're on the internet. The cell membrane is the plastic of the bag.\n\n:-)\nDC\nwww.tigerworld.tv
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I answered this already.\n\nhttp://answers.yahoo.com/question/index;_ylt=AmW0Em3eAdmFrnQMc4_Xilzsy6IX?qid=1006051323791\n\nWorks the same as if you were changing permeability. If you have more Na inside the cell, there is less drive for Na outside the cell to come in. Because Na only has a minor impact on the resting membrane potential, it won't change much, but it will hyperpolarize a bit (away from the Ena and towards Ek).
266097
Okay this is a bit of a complicated question, but i'll do my best, in short these are really very different things.\n\nFirst cell membranes are found in all cells (animal, plant, fungi etc.) they are made up of lipids, generally as a bilayer.  take the membrane from around the outside of a eukaryotic cell, its formed from phospolipids - these molecules have a hydrophilic head [ie will disolve in water/ has a charge] (the phosphate bit) and a hydrophobic tail (the lipid (fat) bit). The hydrophobic bits stick together and the hydrophilic bits are open to the solution on each side (search "lipid bilayer" with yahoo! Images if you want a diagram:-) ).  The outer cell membrane is forming a barrier between the inside and outside of the cell, alowing the cell to control the movment of molecules into and out of itself.  There are a lot of other membranes in the cell apart from the outher cell membrane, the endoplasmic reticulum for example is basicly made up of membrane.\n\nThe cell wall on the other hand isn't present in all cells (we humans (along with all other animals) don't get one). The cell wall is present on the extracellular side of the outer cell membrane.  it is hard and ridgid (unlike the membrane that is fluid) it is made up of lond polymers, and serves to protect the cell.  Plant cell walls are made up of mainly cellulose (in fact when you look at a peice of wood all you are really seeing is the leftover cell walls, and the rest of the cell has long gone).  Fungi also have cell walls but this time not made of cellulose but instead made of chitin, the cell wall still serves the same role however.\n\nIn short the membrane lets the cell control what goes in and out,  and the cell wall provides rigidity.  Membranes are made of lipids (fats) and cell walls of long polemers like chitin and cellulose.\n\nI hope this helps to answer your question, and look for some diagrams - it will make it a lot easier.
121379
Ninhydrin reacts with the lipids from the eccrine glands, which function as sweat glands and rid the body of waste salts.
376047
Ask your doctor about stripping the membranes.  It is basically a rough exam where he/she pushes around inside of you to help things move along.  It is uncomfortable, but well worth it to get the little bun out of the oven.  Worked like a charm for me with my second one.
732986
they are all ways to exchanging substances across a membrane.  \n\ndiffusion is moving down the concentration gradient.  \n\nosmosis is simply the diffusion of water.  \n\nactive transport can be with or against the concentration gradient, but it requires energy from the cell to transport the substance across the membrane.
1180662
The placement of nerve endings, and stimulation of nerve endings
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That is called the "Filtrum"  This may sound a bit disgusting, but it is there to prevent matter from your nose, from entering in to your mouth.  It deflects the "matter" off to the sides.