第二節(jié)(共15小題; 每小題1.5分,滿分22.5分)
請聽下面5段對話或獨白,選出最佳選項。
請聽第6段材料,回答第6至8題。
6. Who is the woman speaking to?
A. Her husband. B. A policeman. C. A fire-fighter.
7. What’s the woman asking for?
A. Advice on safety. B. Money. C. Help.
8. What has happened to the woman’s house?
A. It’s been burnt down.
B. It’s been broken into.
C. It’s been damaged.
請聽第7段材料,回答第9至11題。
9. What does the woman want to know?
A. The best way to go to New York.
B. The quickest way to go to New York.
C. The cheapest way to go to New York.
10. How much does it cost the woman to go to New York by bus?
A. $5. B. $15. C. $50.
11. What do we know from the conversation?
A. The woman will go to New York by bus.
B. It will take the woman five hours to go to New York by bus.
C. The woman won’t go to New York by bus.
請聽第8段材料,回答第12至14題。
12. When will the ballet performances be on?
A. This week. B. Next week. C. Next month.
13. When will the man attend the performance?
A. On Sunday evening.
B. On Thursday evening.
C. On Friday evening.
14. How much does the man pay for the tickets?
A. $20. B. $10. C. $40.
請聽第9段材料,回答第15至17題。
15. What’s the probable relationship between the two speakers?
A. Good friends. B. Strangers. C. Classmates.
16. What can we know about the woman from the conversation?
A. She won a cup in last week’s tennis competition.
B. She is a science expert.
C. She works at St Jude’s Training College.
17. How long has the man been in the science department?
A. Half a year. B. More than a year. C. Two years.
請聽第10段材料,回答第18至20題。
18. How often do people in the Historical Society meet?
A. Every week.
B. Every other week.
C. Every three weeks.
19. What is the main purpose of the Historical Society?
A. To find out what they can learn from history.
B. To study the people in history.
C. To learn about what happened in the past.
20. What do the Historical Society plan to do this year?
A. Study the history of the town.
B. Visit historic houses in the college.
C. Visit more historic places.
第一節(jié)(共5小題;每小題1.5分,滿分7.5分)
請聽下面5段對話, 選出最佳選項。
1. Where does the conversation most probably take place?
A. In a park. B. In a zoo. C. In a pet store.
2. What does the woman mean?
A. Things here are very cheap.
B. Things here are not cheap.
C. She doesn’t know whether things here are cheap or not.
3. Where are the two speakers going to plant the tree?
A. By the front door.
B. At the back of the garage.
C. At the end of the garden.
4. Where does the conversation take place?
A. In a shop. B. In a hotel. C. In a restaurant.
5. What do we learn from the conversation?
A. The man went to New Zealand during Christmas.
B. The man visited New Zealand during the summer holiday.
C. The man’s parents live in New Zealand.
3、時間的控制:做好質壁分離的實驗后,不久就要做質壁分離復原實驗。避免使質壁分離的細胞長時間處于較高濃度的外界溶液中,細胞過度失水而導致死亡。從而觀察不到質壁分離復原的現象。
2、試劑:選用0.3g/ml 蔗糖糖溶液。濃度過高,細胞質壁分離速度雖然很快,但不久就會將細胞殺死,細胞不能進行質壁分離復原;若濃度過低,則不能引起細胞質壁分離或速度太慢。
另外,8% 食鹽溶液、5%的硝酸鉀溶液、一定濃度的尿素、甘油……也可使用,但后面三者在引起質壁分離后可自動復原。
1、選材:選取紫色洋蔥鱗片葉外表皮。其細胞液為紫色,在顯微鏡下與無色透明的細胞壁容易區(qū)分,觀察到的質壁分離和復原效果明顯。
另外,取新鮮水綿、黑藻葉、南瓜表皮也可以做這個實驗。
2、動物細胞能發(fā)生滲透作用但不會發(fā)生質壁分離。
例題:下面是一組用新鮮洋蔥表皮進行的實驗處理和結果,請分析回答:
實驗分組 |
處理方法 |
實驗結果 |
第1組 |
①將材料置于30%蔗糖溶液中 |
①發(fā)生質壁分離 |
②然后將材料移至蒸餾水中 |
②發(fā)生質壁分離復原 |
|
第2組 |
③將材料置于60%蔗糖溶液中 |
③迅速發(fā)生質壁分離 |
④然后將材料移至蒸餾水中 |
④質壁分離不能復原 |
|
第3組 |
⑤將材料置于7%的尿素溶液中 |
⑤開始發(fā)生質壁分離,然后逐漸自動復原 |
第4組 |
⑥將材料放入100℃熱水中3min后取出,重復第1組實驗 |
⑥不發(fā)生質壁分離 |
(1)洋蔥表皮細胞在第1、2、3組實驗中均發(fā)生了質壁分離現象,其內部結構基礎和外在條件分別是 。
(2)比較第1和第2組實驗結果的差異,說明 。
(3)比較第1和第3組實驗結果,出現實驗結果差異性的原因是 。
(4)比較第1和第4組實驗結果,出現實驗結果差異性的原因是 。
答案:(1)內部結構基礎是有原生質層和原生質層內外兩個溶液體系的存在;外在條件是原生質層內外兩個溶液體系存在濃度差
(2)高濃度溶液加快質壁分離現象的出現,但由于引起細胞過度失水,導致細胞死亡,使質壁分離復原不能發(fā)生
(3)尿素是可能被細胞主動吸收的小分子物質,隨著尿素分子不斷的進入細胞內部,當細胞內外濃度趨于一致時,質壁分離就會自動復原
(4)高溫致使細胞死亡,死亡的細胞原生質層失去選擇透過性,不能發(fā)生質壁分離
注意問題
1、細胞發(fā)生質壁分離后,細胞壁與細胞膜之間的空隙充滿的是0.3mg/mL蔗糖溶液。
2.方法步驟:
應用:1、可以用于測定細胞液的濃度 2、可以用于判斷細胞的死活
注意問題:
1.原理:成熟(有明顯液泡)的植物細胞能夠與外界溶液組成一個滲透系統,通過滲透作用的方式吸水或失水。
4、結論: 細胞外溶液濃度 > 細胞內溶液濃度,細胞失水 質壁分離
細胞外溶液濃度 < 細胞內溶液濃度,細胞吸水 質壁分離復原
植物細胞質壁分離和復原
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