还原性糖（Reducing sugar）
Reducing sugar, reducing sugar: reducing sugar, including glucose, fructose, galactose, lactose, maltose, etc..
Non reducing sugars include sucrose, starch, cellulose, etc., but they can be reduced by hydrolysis to produce the corresponding reducing monosaccharides.
Reducing sugar concept: reducing sugar means reducing sugar. In sugar, a monosaccharide containing a free aldehyde group or ketone group and two sugars containing a free aldehyde group are reducible.
Glucose molecules contain free aldehyde groups, fructose molecules contain free ketone groups, lactose and maltose molecules contain free aldehyde groups, so they are reducing sugar.
Identification of reducing sugar
Fehling reagent biuret reagent composition and method of using the same, but the two and not the same principle. Fehling reagent reagent test and class are reducing reagent sugar, there is also the difference between the two methods and principle, composition, following on from the aspects of the pri
nciple of the use of several reagents, composition and methods of use to do a simple summary.
1. the Fehling reagent and biuret reagent
Fehling reagent and biuret reagents are composed of solution
and the solution, but the two have the following three different:
(1) the solution concentration is different
The solution for a Fehling reagent Fehling Reagent (NaOH solution) the concentration of 0.1g/ml, ethylene Fehling Reagent (CuSO4 solution) the concentration of 0.05g/ml; biuret reagent: A biuret reagent (NaOH solution) the concentration of 0.01g/ml, biuret reagent B (CuSO4 solution) was 0.01g /ml.
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(2) the principle of use is different
Is a new preparation of Fehling reagent solution, it reacts with aldehyde in heating conditions were reduced to brick red precipitate, can be used to identify the presence of soluble reducing sugar. Identification of soluble reducing sugar by Fehling reagent, the color change of the process solution for shallow blue, brown and red brick (precipitation).
Whether the identification of biological tissues contain protein, commonly used biuret method, using the biuret reagent, the biuret reaction is. Biuret reaction essence is purple reaction in alkaline environment and biuret reagent. Which contains a lot of protein molecules and biuret () peptide bond structure similar, so the protein can occur color reaction with biuret reagent, with biuret reagent identification of proteins exist.乔任梁告别仪式
(3) different methods of use;
The Fehling reagent used, first solution and mixed solution (the drops of the solution into the solution), then immediately use: when using the biuret reagent, adding solution (2mL), shaking it, the reaction caused by alkaline environment, then add 3~4 drops of solution, oscillation observed after shaking phenomenon.
2. and Fehling reagent Benedict reagent.
中国梦之声下载About Fehling reagent and class reagent, the following examples available leads to the similarities and differences: example: you can use what method, test whether human urine contains sugar?
Answer：
Method: adding human urine 0.1mL in vitro, adding Bancroft sugar qualitative reagent 1mL, after mixing, the tube is placed in boiling water in a beaker boiling for 1min~2min, if the tube in solution after heating the brick red precipitate, that contain sugar in the urine.
Method two: take a little urine diluted with water, adding just prepared Fehling reagent well, boiling water bath, if the brick red precipitate, that contain sugar in the urine.
Method three: take a little urine diluted with water, add a little suspension (New) heating, if the brick red precipitate, that contain sugar in the urine.broken mirror
Yinfeilin reagent is essentially the freshly prepared
王子变青蛙下载solutions, so the essence of method two and method three is the same, just view is different.
From the above examples can be seen, and the class Fehling reagent reagent can be used for identification of soluble reducing sugar (in the previous exercise test is the presence of glucose) two have the same point, there are different points.
The differences between the two can be summed up in the following points:
(1) class identification reagent used in the urine,
The formula and Fehling reagent is not the same, the formula is:
400mL add 85g sodium citrate and 50g anhydrous sodium carbonate in water;
50mL added anhydrous copper sulfate into 8.5g heated water. Make solution;
宋祖英的情人Put the solution into sodium citrate solution, while still mixing, such as precipitate can filter.
(2) the reaction principle and Fehling reagent is slightly different. Using Fehling reagent identification, Fehling reagent A and B direct reaction of Fehling reagent and soluble sugar produced by the reaction of brick red precipitate. The reagent produced in the class is like this: sodium citrate and sodium carbonate were NaHCO3, produced in the water they can
hydrolyze, combined with sodium citrate solution and mixed solution, and red precipitate and glucose aldehyde reaction brick.
(3) the preservation of the two reagents is different. Fehling reagent A and B can produce strong Fehling reagent, easy to precipitate, therefore the Fehling reagent is generally now equipped with; and Bancroft reagent formula, sodium citrate as a buffer material, produce a limited number of concentration and the mixed solution is relatively low, not easy to precipitate, therefore the reagent c
an be stored for a long time.
Of course, regardless of class or reagent Fehling reagent are, after all with the aldehyde in a boiling water bath heating conditions react brick red precipitate, the reaction phenomenon, this is the two in common.
Preparation of experimental materials for identification of soluble reducing sugars
Plant tissues are commonly used experimental materials, but they must be chosen. In dicotyledonous plants, the principal photosynthetic product, glucose, is formed into starch and temporarily stored in leaves, so it is better not to use the leaves of dicotyledonous plants as experimental material. Some monocot plants such as leek, iris, is the initial product of photosynthesis into starch, therefore leaves contain lots of soluble monosaccharides, but because chlorophyll darker, for the identification of the color reaction plays a role to cover, the experimental phenomenon is not obvious, therefore, should