网址：http://m.1010jiajiao.com/timu_id_2270120[举报]
实验一：将空白琼脂和含EDTA的琼脂做成帽状，分别套在甲、乙两组玉米胚根的根冠外（示意图如下）。提示：EDTA的作用是去除与其临接部位的 Ca2+。
将胚根水平放置培养一定时间后，观察到甲组胚根向重力（下）生长，乙组胚根水平生长。根据上述实验结果，得出实验结论： 。
实验二：水平放置的胚根弯曲向下生长，与根冠近地侧的Ca2+浓度明显高于远地侧有关。研究表明，根总是朝着Ca 2+浓度高的方向弯曲生长。为验证这一结论，有人设计了下列实验方案。请根据提供的实验材料和用具，写出第二步及以后的实验步骤和实验结果，并回答问题。
（1）实验材料和用具：胚根等长的萌发玉米种子，空白琼脂帽，含EDTA的琼脂帽，上面部分含Ca2+的琼脂帽（水平方向），培养皿等。
（2）实验步骤：
第一步：取若干个培养皿，在每个培养皿中放置适量的萌发玉米种子，按实验一中乙组的方法处理胚根一定时间后，移去根冠外的琼脂帽。然后将培养皿平均分成两组，编号为 A组、B 组。
第二步： 。
第三步： 。
（3）实验结果： 。
（4）科学家进一步证实，根冠中生长素的分布受Ca2+浓度影响，当胚根水平放置时，重力诱导Ca2+向根冠下侧移动，导致近地侧的生长素浓度比远地侧高。请分析胚根的生长素分布与向重力生长的关系： 。 查看习题详情和答案>>
（1）若图甲是癌细胞的细胞膜，则膜上含量较正常细胞减少的物质是[ ] 。
（2）若图甲是线粒体膜，b和c过程运输的气体分别是 。b、c运输方式符合图 所表示的物质运输曲线。
（3）若图甲表示人体红细胞膜，则表示Na＋、K＋运输的分别是图中 。Na＋、K＋的运输方式符合图 所示曲线。
（4）已知红细胞吸收葡萄糖是协助扩散，而有人认为小肠上皮细胞以主动运输的方式吸收葡萄糖，请设计实验加以确定。
①实验步骤：
第一步：取甲、乙两组生理状况相同的小肠上皮细胞，放入适宜浓度的含有葡萄糖的培养液中。
第二步：甲组细胞给予正常的呼吸条件， 。
第三步： 。
②预测实验结果并分析：
a．若甲、乙两组细胞对葡萄糖的吸收速率基本相同，则 。
b． 。 查看习题详情和答案>>
阅读短文，在其后空白处写出各单词的正确形式。单词的第一个字母已经给出。
The worst traveler in the world was Paul of San Francisco. Once he f____1. from the U.S. to his hometown in Italy to see someone at home. The plane made a one-hour stop to get oil at an airport in New York. Paul thought he was in Rome. C____2., he got off the plane.
When nobody was there to meet him, Paul thought maybe the heavy t____3. made his friends late. While looking for their address, Paul found that the old “Rome”had changed a lot. He found many high m____4. buildings instead of old ones. He also found that many people spoke English but not Italian and that many street signs were w____ 5. in English.
Paul knew very l____6. English. So he asked a policeman in Italian the way to the bus station. He happened to meet a policeman who was also born in Italy and answered in the same l____7..
After twelve hours’ traveling round on a bus, the driver handed him over to a____8. policeman. But this time, this policeman could only speak English. So paul asked the policeman why the Rome police employed（雇佣）so many people who spoke English as policemen.
Paul didn’t b____9. he was in New York when he was told so. To get him on a plane to Italy, he was s____10. to the airport in a police car.
查看习题详情和答案>>
阅读下面阅读材料，然后从各小题所给的四个选项中选择一个最佳答案。
Henry: I find the Internet is very good for shopping. I use more and more for buying books and CDs, and I even bought some clothes over the Internet. The other thing I can do is to book(预订) travels over the Internet. I booked a cheap flight once. It was very easy, and it was really good.
David: I use the Internet for games. I play chess with people all around the world. Last night I had a game with someone from Japan. I also download (下载)games from the Internet, so I can have any game I want.
Peter: I use the Internet for anything I need to help me with my schoolwork. I use the online dictionaries, encyclopedias(百科全书) and magazines. It’s great because I can download pictures or articles and use them to help my homework. It’s very easy to use and it’s free, so I like it.
Tony: Well, the main thing I use the Internet for is to e-mail. I usually write to my customers(顾客) by e-mail, and my customers answer me by e-mail, too. We probably send and receive four or five hundred e-mails a month. But of course, I also use e-mails to keep in touch(保持联系) with friends and family. My daughter is in Australia and we send e-mails to each other every day.
1.________ prefers to use the Internet to buy things.
A. Henry?????? B. David??????? C. Peter?????? D. Tony
2. David’s hobby is to __________?? on the Internet.
A. read books?? B. book flights??
C. play games?? D. download pictures
3.Peter can use the Internet to ____________easily.
A. play chess? B. do schoolwork
C. do some shopping D. talk with his daughter
4.From the passage we know that ???? .
A. Peter is a teacher??????????? B. Tony is a businessman
C. David is an engineer???????? D. Henry is a bookseller
5.Which of the following is NOT true?
A. Henry had an experience of using the Internet to book a cheap flight.
B. David had a game with a Japanese over the Internet one night.
C. Tony often e-mails to his customers, friends and family.
D. Peter needs to pay for what he gets from the Internet.
查看习题详情和答案>>
I am a middle-school student. Now let ___1___ tell you something ___2___ our classroom.
It's very ___3___. There are two maps ___4___ the back wall. ___5___ is a map of China.
___6___ is a map of the world (世界).
There are ___7___ desks and chairs in our classroom. There is a big desk ___8___ the
teacher in the front of it. We ___9___ four classes in the ___10___ and two in the afternoon
1. a. I b. my c. me d. we
2. a. about b. in c. on d. at
3. a. small b. big c. bigger d. biggest
4. a. in b. on c. under d. over
5. a. It b. It's c. One d. one
6. a. Other b. Others c. Another d. The other
7. a. fourty b. forty c. forteen d. fourteenth
8. a. for b. of c. to d. about
9. a. there is b. there are c. has d. have
10. a. moning b. mourning c. morning d. moring
查看习题详情和答案>>