问题 探究题

七年级1班生物兴趣小组的几位同学在做“馒头在口腔中的变化”的探究实验时,采用了不同的处理方法,具体如下:

1号试管:加入馒头碎屑和2毫升唾液,并充分搅拌;

2号试管:加入馒头碎屑和2毫升清水,并充分搅拌;

3号试管:加入馒头块和2毫升唾液,但不搅拌。

将3支试管都放入37℃的温水中保温10分钟,取出冷却后分别加入2滴碘液,摇匀后观察试管中馒头的颜色变化。请问:

(1)1号试管馒头碎屑没有变色,原因是馒头中的__________在________酶的作用下变成了麦芽糖。

(2)2号试管馒头碎屑变色的原因是                      

(3)3号试管馒头块变色的原因是_________                 _。

(4)该实验成功可以说明淀粉在消化道的_________开始被消化。

答案

(1)淀粉 唾液淀粉

(2)未加唾液,淀粉没有分解,遇碘液变蓝

(3)馒头不能与唾液充分混合,淀粉没有全部分解,遇碘液变蓝

(4)口腔

碘液是用来检验淀粉的存在的,因为淀粉遇到碘液会变蓝,唾液中含有唾液淀粉酶,能将淀粉进行初步消化,2号试管加的不是唾液,是清水,是作为对照实验,3号试管尽管加了唾液,但由于是馒头块,唾液不能将淀粉完全消化,所以滴加碘液仍然会变蓝。

判断题
单项选择题

阅读以下信用证,做选择填空。
(1)信用证内容
27: SEQUENCE OF TOTAL 1/1
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B.不清洁已装船提单

C.备运提单