硫酸盐
碱性的
硫酸铜（蓝色溶液） 在碱性条件下被还 原为氧化铜，在相 同条件下产生砖红 色沉淀。
Cu2+ Blue
+
e-
Cu+ Red
半定量的

The test is semi-quantitative – the greater the concentration of reducing sugar,the darker and heavier the precipitate.
任何必要的加热应在固定的时间内水浴加热
A control
blank (a volume of water equal to the volume of text solution)should be run alongside the tests;any colour change in the blank would suggest contamination or unreliable technique.不可靠的，不可信任的
向样品中加入5ml乙醇混合 后，加5ml水，振荡。
Ⅲ
• Positive result (milky-white suspension =emulsion)=fat or oil present
阳性结果：形成乳浊液， 说明脂肪或油脂存在。
充满油的

Principle:the fat or oil dissolves in the ethanol,which is miscible with water.When the oil-laden ethanol is added to the water the oil is left as minute drops suspended in the water – these drops scatter light rays in many directions and give the suspension a milky-white v.悬浮 appearance.
阳性结果：溶液呈深紫 色，说明有蛋白质存在。
n.碱；adj碱性的
氢氧化钠
Principle:the
alkali (sodium hydroxide)hydrolyses the protein into fragments containing the peptide linkage –CO-NH– which then forms coloured complexes with copper (II) from the copper sulphate. 碱将蛋白质水解成包含肽键的碎 片，然后肽键与硫酸铜中的2价铜 离子反应生成颜色复合物。
实验是半定量的，还原糖含量越多， 沉淀越深、越多。
CONCENTRATION OF REDUCING SUGAR
还原糖含量
COLOUR OF SOLUTION AND PREቤተ መጻሕፍቲ ባይዱIPITATE
BLUE GREEN YELLOW
0
溶液及沉淀颜色
INCREASING PALE BROWN 浅褐色
ORANGE RED
将脂肪或油脂溶于乙醇，并与水混溶。当含油乙醇加入到 水中后，油脂会分散成小油滴悬浮在水中，这些油滴折射 出许多光路，令悬浮液呈乳白色。
Ⅰ
双缩脲 试剂
• Test with Biuret reagent
Ⅱ
• Positive result (mauve-purple coloration)=protein present
Positive result (green to orange-red precipitate)=nonreducing sugar present
阳性结果：产生红黄色沉淀， 说明非还原糖存在
More intensely-coloured precipitate=both reducing and non-reducing sugars present
污染
空白对照（等体积的水与待测溶液）应在实验时同 时进行；在对照组中任何颜色的改变都表明实验被 污染或者技术不可靠。
REMEMBER SAFETY PROCEDURES
程序，步骤
1.
2.
Wear eye protection when heating solutions. Use a safety移液管 pipette – no 移液 pipetting by mouth.
为了使这些检测结果具有比较性，我们可以去 比较几种不同待测溶液中蛋白质的含量，而且必须 要使尽可能多的因素保持不变。
― ― ―
Equal volumes of reagents should be used in each test; 每组实验使用等量的试剂 Results should be compared after equal time 间隔，间距 intervals; 相同时间间隔后比较实验结果 Any necessary heating should be carried out in a water bath for a fixed period of time; 进行，完成
阳性结果：溶液 变成蓝黑色，说 明淀粉存在
结合到……

Principle:iodine binds to the centre of the starch helix,forming a starch-iodine complex which is intense blue-black in colour.
本尼迪特试剂
阴性结果：溶液仍 然为蓝色，说明不 存在还原糖
Heat with 2 cm3 Benedict’s reagent
阳性结果：产生红黄 色沉淀，说明存在还 原糖
Negative result (solution remains clear blue)=absence of reducing sugar
1.加热溶液时戴上护目镜。 2.使用安全的移液器，不要用嘴移液。
姓名： 学号：
碘结合到淀粉螺旋的中心，形成一种 强烈的蓝黑色 淀粉-碘 复合物。
Ⅰ
• Remove a 2 cm3 sample
乳液，乳化剂
Ⅱ
• Perform emulsion test (add 5cm3 of ethanol to sample – mix –add to 5cm3 water - shake)
peptide linkage肽键
N.B.
In order to make these tests comparative,e.g.to compare the amount of protein present in several different test solutions,it is essential that as many factors as possible are maintained constant. 基本的， 必要的 不变的 For example,
产生颜色更深的沉淀，说明还 原糖与非还原糖同时存在
•Principle:Copper (II) sulphate,which forms a blue solution under alkaline conditions,is reduced to copper (I) oxide,which forms a brick-red precipitate under the same conditions.
TESTING FOR BIOCHEMICALS

Aqueous solution,suspension or extract of test substance.
aqueous adj.水的，水般的 suspension n.悬浮，悬浮液
待测物质的水溶液或悬浮液。
Remove a 2 cm3 sample
Remove a 2 cm3 sample 碘 add a drop of Iodine solution (iodine in potassium iodide solution) 钾 Positive result (blue-black coloration)=starch present
加入一滴 碘溶液
Positive result (green to orange-red precipitate)=reducing sugar present
水解 中和
Hydrolyse with dil.HCl and neutralize with NaHCO3
浓盐酸
浅蓝色 溶液
Heat with 2 cm3 Benedict’s reagent