9.Why is the man interested in such news?
A.Because he hopes to go to the moon.
B.Because he is an astronaut.
C.Because he wants to do research in space.
听第8段材料,回答第10至12题。
8.What was the news about?
A.It’s about the space station.
B.It’s about the space.
C.It’s about the astronauts.
7.Why does the woman think New York is a nice place to live?
A.It has a large population.
B.It offers an exciting life.
C.It’s interesting and quiet.
听第7段材料,回答第8至9题。
6.Where does the man probably live?
A.In the countryside. B.In a big city. C.In America.
4.What conclusion can we draw from the conversation?
A.John had been working hard.
B.John probably didn’t work hard.
C.The woman was sorry to hear the news.
3.What did the woman buy for her husband?
A.A stamp. B.A watch. C.A toy
2.What does the woman want to buy?
A.Cameras. B.Pictures. C.Films.
1.Where are the two speakers?
A.In a restaurant. B.In a
hotel. C.In th
e street.
35.(10分)红薯和土豆都富含淀粉,但红薯吃起来比土豆甜。为探究其原因,某兴趣小组在不同温度、其它条件相同的情况下对处于休眠期的红薯块根与土豆块茎处理30分钟后测定还原糖的含量。结果如图:
![]()
(1)由图中曲线可知,60°C时红薯还原糖含量最高,原因 。
(2)土豆不含还原糖的原因是 。
(3)为了确定土豆不含淀粉的原因,请完成以下实验:
实验原理:①淀粉能被淀粉酶水解为还原糖;
②
。
备选材料与用具:去掉淀粉与还原糖的红薯提取液,去掉淀粉的土豆提取液,双缩脲试剂A液,双缩脲试剂B液,斐林试剂A液,斐林试剂B液,苏丹红染液,3%淀粉溶液,3%蔗糖溶液等。
实验步骤:
第一步:取A、B两支试管,在A试管中加入去掉淀粉的土豆提取液2 ml,在B试管中加入去掉淀粉与还原糖的红薯提取液2 ml。 水浴保温5分钟。
第二步:向A、B两试管中加入等量的水浴加温至60°C的 溶液。水浴保温5分钟。
第三步:将
后,向A、B试管内各加入2 ml。然后,
。
最可能的实验结果: 。
(4)食用土豆时,消化分解成的葡萄糖,几乎被小肠上皮细胞全部吸收,该吸收过程需要 。糖尿病人食用较多土豆,吸收的葡萄糖不同于常人的代谢出路是 。
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