It may seem easy to say that plants and animals are different. Any child can tell the difference between  a tree and a dog. But those differences are far deeper than just what they look like. The cells (細胞) that plants are made up of are different. In other words, the cell wall of plants has something special.

First of all, it's important to find that not all plant cells have a cell wall. Besides, there are many differences of a cell wall based on the kinds of plant. The following is meant to be what a plant cell wall is  like.

  The cell wall of a plant is on the outside of the cell membrane (膜). It is usually hard and cannot be bent easily, but the degree of flexibility (韌性) of the cell wall is different. It is based on the special use that the cell has in keeping the plant alive. Cells that make up the trunk of a tree are clearly less flexible than? cells on a leaf.

     Cell walls act in many ways. They serve to protect the plant. They provide support, as well as help in the movement of chemicals and wastes into and out of the cell.  More importantly, they control the water? that goes in and out.  Plants must have good water controlling systems (系統(tǒng)), allowing them to keep water during dry seasons, and get rid of unnecessary water. Plants can't walk around to find water, so  being able to control water is very important.

So there you have it , what a plant cell wall is. Of course, there are many other things that are not talked about here. Knowing more about plant cell wails requires further study and research.

1.From the first two paragraphs we can find that _____.

A. all plants have a ceil wall?????????????

B. plant cells and animal cells are the same

C. different kinds of plant have different cell walls

D. there are no differences between the cells of a tree and a dog

2.The underlined word "bent" in the passage is the closest in meaning to _____.

A. 變形的 ?? B. 防水的   ? C. 太陽灼傷的     ??? D. 表皮破損的

3.Cells in the trunk of a tree are _____ those on a leaf.

A. as flexible as             ?????????  B. not so flexible as

C. more important than                ?? D. less important than

4.What is the most important use of a plant cell wall?

A. To protect the plant.                ???? B. To provide support.

C. To move chemicals and wastes.       D. To control the water.

 

【答案】

1.C

2.D

3.B

4.D

【解析】

試題解析:本文大意：也許很容易說植物與動物不同，任一孩子能講出一棵樹和一只狗的區(qū)別。但那些區(qū)別遠比它們看上去的要深。 組成植物的細胞是不同的，換句話說，植物的細胞壁有特殊的東西。 首先不是所有的植物有細胞壁，另外，基于植物的種類細胞壁有很多不同。細胞壁在細胞膜的外面。通常堅硬不易破損，但柔韌性的程度不一樣。細胞壁也多種方法工作來保護植物。更重要的是，控制水的出入。

1.細節(jié)理解題。根據(jù) there are many differences of a cell wall based on the kinds of plant. 基于植物的種類細胞壁有很多不同，可知答案選C

2.推理判斷題。根據(jù)It is usually hard通常堅硬 ，可知答案選D

3.細節(jié)理解題。根據(jù)Cells that make up the trunk of a tree are clearly less flexible than? cells on a leaf.組成樹干的細胞很明顯沒有樹葉的細胞柔韌，可知答案選B

4.細節(jié)理解題。根據(jù) More importantly, they control the water? that goes in and out.更重要的是，控制水的出入 ，可知答案選D

考點：科普類短文閱讀。

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