阅读理解。
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 (细胞) that
plants are made up of are different. In other words, the cell wail 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 (韧性) 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 wails 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 (系统), 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. The best title of the passage can be _____.
A. Different Plants
B. Different Animals
C. The Plant Cell Wall
D. The Uses of Cells
2. 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
3. The underlined word "bent" in the passage is the closest in meaning to _____.
A. shape-changed
B. water-kept
C. sun-burnt
D. skin-broken
4. 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
5. 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.
