How does cellulose differ from starch and glycogen in its reaction to iodine?
Cellulose does not give a color change with iodine. reacts with starch producing a blue black color. Iodine solution will also react with glycogen, although the color produced is browner and much less intense.
What is the test for cellulose? e.g. iodine for starch, benedicts for sugars...?
i need help on it as well, got it for homework. i found 'shultz/schultz solution'. i know it definitely has something to do with it. if you do find the answer,can you please post it on this page- thanks.
What is the structural difference between starch and cellulose?
In starch, the sugar molecules are linked together such that they are all in the same orientation. In cellulose, they are linked together such that alternating molecules are rotated 180 degrees from each other. This seemingly minor change makes cellulose much stronger than starch, because parallel cellulose fibers stack up just like corrugated sheets piled on top of each other. The fibers hydrogen-bond to each other, providing enormous structural strength. The fibers of starch, by contrast, bind to each other much more weakly and thus fall apart more easily.Some kinds of starch (glycogen and amylopectin) are formed out of branching chains, while other kinds (amylose) are linear polymers. The latter are much harder for the body to break down, because they coil tightly into a helical form. Cellulose is only formed out of linear chains, because branches would substantially reduce its strength by disrupting the strong bonds between parallel fibers.The alternating structure of cellulose also makes it much more difficult to digest. In fact, most organisms lack this capacity entirely whereas almost all organisms can digest starch. I’m not sure exactly why there is such a huge difference between the stability of alpha (starch) vs. beta (cellulose) glycosidic bonds, but this difference has enormous consequences for the ecology of Earth.
Why starch is blue with iodine, but not with cellulose though it is polymer in nature?
I’m sure that someone can give a better answer than this - but starch is very long molecule that is wound into a spiral (helix). The molecule appears white to our eyes.In the presence of iodine, the iodine finds its way into the spiral of the starch molecule and the weak bonds it forms change the energy levels in the iodine just enough to produce a colour change.This colour change is incredibly sensitive to the presence of iodine which means that starch can be used as an indicator for the presence of iodine in redox titrations that produce iodine.Note: stricly speaking it isn’t iodine, but the complex formed between the insoluble iodine molecule, I2 and the soluble iodide anion, I^(-), to form the soluble triodide anion, I3^(-) that is detected - which is why titrations need to have KI present as well as starch in order to work.If you forget the KI, believe me, you can use a lot of titrant before you realise something is amiss LOL.
Why does the color of iodine solution turn blue when starch is added to it?
I hope this will help :What properties of starch (given its chemical structure) allow it to be used as an indicator? Davender Khera, Yale UniversityWhen starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color.The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into iodine and iodide and the color disappears.BTW...there is something known as GOOGLE. Next time you have such kind of doubts, please feel free to use it
What is the difference between glucose and starch?
UMmmm i think i remeber this from life science glucose is used in a formula for photosynthesis and starch is part of sugar sord of like it. I dont guarantee this is the right answer so double check first.
How can you tell by using Benedict's and iodine solutions if a sugar is a Monosaccharide, Disaccharide, & poly
If upon adding iodine to the solution it turns a deep blue you have polysaccharide's presenty Benedict's reagent is used as a simple test for reducing sugars. A reducing sugar is a carbohydrate possessing either a free aldehyde or free ketone functional group as part of its molecular structure. A monosaccaride and some disaccharides would have these functional groups available.
What is the difference between amylose and cellulose?
Amylose is a linear polymer of glucose linked with mainly α(1→4) bonds. It can be made of several thousand glucose units. It is one of the two components of starch, the other being amylopectin. Amylose structureThe α(1→4) bonds promote the formation of a helix structure. The structural formula of amylose is pictured at right. The number of repeated glucose subunits (n) can be many thousands (usually in the range of 300 and 3000). Amylose starch is less readily digested than amylopectin. However it takes up less space so is preferred for storage in plants; it is about 20% of the starch in plants is stored. The digestive enzyme amylase works on the ends of the starch molecule, breaking it down into sugars. Iodine molecules fit neatly inside the helical structure of amylose, binding with the starch polymer, causing it to absorb certain wavelengths of light. Hence, a common test for starch is to mix it with a small amount of yellow iodine solution. In the presence of amylose a blue-black colour will be observed. The intensity of the colour can be tested with a colorimeter using a red filter, to indicate the concentration of starch present in the solution. High-amylose varieties of rice have a much lower glycemic load, which could be beneficial for diabetics. Cellulose is an organic compound with the formula (C6H10O5)n. It is a structural polysaccharide derived from beta-glucose. Cellulose is the primary structural component of green plants. The primary cell wall of green plants is made of cellulose; acetic acid bacteria are also known to synthesize cellulose, as well as many forms of algae, and the oomycetes. Cellulose was discovered and isolated in the mid-nineteenth century by the French chemist Anselme Payen and, as of the year 2006, the estimated annual production of 1.5x109 tonnes. Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms (see methanogen). Cellulose is not digestible by humans and is often referred to as 'dietary fiber' or 'roughage', acting as a hydrophilic bulking agent for feces.
Why does cellulose not test positive with iodine?
Cellulose is insoluble due to the shape it takes. It is formed as very long threads of beta-glucose synthesized from a ring of cellulase enzymes. Every other glucose is inverted allowing the ring of linear polymers to lie very close beside each other forming crystals. Intermolecular hydrogen bonding between the strands holds the cellulose polymers in the ribbons and excluding the entry of water molecules. This strand cannot react with iodine. Amylose starch is linear and the monomers of glucose are connected by an alpha acetal linkage. Each strand is each made of 1000's of glucose molecules joined together. The alpha acetal bonds allow the strand to spiral and provides a place for the iodine to hide from the water because iodine is only slightly soluble in water. http://www.elmhurst.edu/~chm/vchembook/5...
Why does cellulose not give any colour in an iodine test?
Cellulose is derived from D glucose units which condensed through beta glycosidic bond.This give a cellulose to be straight polymer, therefore,it can't coil around iodine to produce blue color as starch does.