问题 填空题

如图是两个细胞模式图

(1)如果表示洋葱表皮细胞结构的应该是______图,如果表示人的口腔上皮细胞结构的则是______图.

(2)图中A、的[1]是______,起保护和______细胞的作用,鲜嫩的蔬菜细胞中,该结构应该较______(填“薄”或“厚”).

答案

由图可知:在图A中[1]细胞壁,[2]细胞膜,[3]细胞核,[4]细胞核,[5]液泡.

植物细胞与动物细胞的区别:植物细胞具有细胞壁、叶绿体和液泡,动物细胞不具有细胞壁、液泡、叶绿体.

植物细胞与动物细胞的联系:都有细胞膜、细胞质、细胞核、线粒体.

(1)图 A,具有[1]细胞壁、[5]液泡是洋葱表皮细胞,洋葱表皮不含有叶绿体;图B中不具有[1]细胞壁、[5]液泡.是人的口腔上皮细胞.

(2)细胞壁是细胞外围的厚壁.是植物细胞特有的结构,具有保护和支持作用,并与植物细胞的吸收,蒸腾和物质的运输有关.细胞壁分为 3层,即胞间层(中层)、初生壁和次生壁.胞间层把相邻细胞粘在一起形成组织.初生壁在胞间层两侧,所有植物细胞都有.随着细胞的生长细胞壁是越来越厚的.刚刚形成的细胞可能只有胞间层,而生长很久的细胞壁就可能同时具有胞间层,初生细胞壁,和次生细胞壁.因此,鲜嫩蔬菜细胞中的细胞壁薄.

故答案为:(1)A;B;(2)细胞壁;支持;薄.

选择题
阅读理解

It is common for older people to forget things. Now an American study has found that memory starts to fail when we are young adults. People younger than thirty years of age usually do not know that they are starting to forget information. But scientists from the University of Michigan say the loss of memory has usually already started.

Researchers say people do not observe this slow reduction in mental ability until the loss affects their everyday activities.

Denise Park led the new study. She directs the Centre for Aging and Cognition at the Institute for Social Research at the University of Michigan. Her team studied more than 350 men and women between the ages of twenty and ninety years. The study identified people in their middle twenties with memory problems.

She says young adults do not know they are forgetting things because their brains have more information than they need.

But she says that people in their twenties and thirties are losing memory at the same rate as people in their sixties and seventies.

Ms. Park says people between the ages of sixty and seventy may note the decrease in their mental abilities. They begin to observe that they are having more trouble remembering and learning new information.

The study found that older adults are more likely to remember false information as being true. For example, they remembered false medical claims as being true. Younger people remembered hearing the information. But they were more likely to remember that it was false.

Ms. Park is now using modern imaging equipment to study what happens in the brains of people of different ages. She is studying what parts of the brain older adults use for different activities compared to younger adults. Ms. Park says mental performance is a direct result of brain activity and brain structure. She says keeping the brain active is important. She hopes future studies will identify ways to improve the operation of our aging minds.

小题1:The passage is meant to _____________.

A.emphasize the importance of exercising the brain

B.analyze the difference between different age groups on the loss of memory

C.reveal the decrease in mental ability of young adults as well as older adults

D.introduce effective ways to improve memory小题2: According to the passage, young adults differ from older adults in that ________.

A.they lose their memory at a slower rate

B.they rarely realize they have memory problems

C.their brains can store much more information

D.all of the above小题3: Which of the following statements is NOT TRUE?

A.Not until the loss of memory affects their daily activities, do people notice the decrease in their mental abilities.

B.People begin to lose memory in their twenties.

C.Older people tend to remember false information as being true.

D.Younger people find it easier to remember the information that is proven false.小题4:It can be inferred from what Denis Park says that ______.

A.mental performance can be improved

B.mental ability is determined entirely by brain structure

C.people of different ages use different parts of the brain for memorizing

D.different parts of the brain are responsible for different mental activities小题5:Which of the following is a suitable title for the passage?

A.The Mysterious Brain

B.The Ability to Forget

C.Memory Reduction

D.Mental Performance