问题 单项选择题

层粘连蛋白分子是由一条重链(A链)和两条轻链(B1、B2链)构成的高分子糖蛋白,作为细胞的结构成分,它含有多个结合位点,对细胞间粘连及细胞的分化等都有作用。层粘连蛋白分子结构示意图如图,若该蛋白分子由m个氨基酸构成,下列有关说法不正确的是()

A.该层粘连蛋白分子含有的肽键数为m-3

B.该蛋白在细胞识别中具有重要作用

C.癌细胞膜相对正常细胞膜而言表面的层粘连蛋白少

D.该物质的合成只需核糖体即可完成

答案

参考答案:D

解析:

层粘连蛋白是由3条肽链构成,含有肽键数为m-3;图中显示该蛋白质有细胞膜表面结合受体,说明该蛋白在细胞识别中具有重要作用,根据癌细胞特点也可说明癌细胞膜表面层粘连蛋白减少;糖蛋白的合成在核糖体、加工在内质网(加糖基),还需要线粒体提供能量。

考点:本题考查蛋白质的相关知识,意在考查考生理解所学知识的特殊性,把握知识的识记和运用能力。

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     If you want to improve your child's results at school, you could do a lot worse than ensuring that they

do plenty of exercise.Scientists have already shown that physical activity can make you brainier.But

a team in America has used scans to show that an important part of the brain actually grows in children

who are fit.These youngsters tend to be more intelligent and have better memories than those who are

inactive.

     Scientists also found that one of the most important parts of their brains was 12 percent larger than

those of unfit children.They believe that encouraging children to take exercise from a very young age

could help them do better at school later.Researchers from the University of Illinois, in the U.S.,

studied the brains of 49 children aged nine and ten using a magnetic resonance imaging scan (核磁共振

摄影扫描), a technique which provides very detailed pictures of organs and tissues in the body.

     They also tested the fitness levels of the children by making them run on a treadmill (跑步机).The

scientists found that the hippocampus, a part of the brain responsible for memory and learning, was around

12 percent larger in the fitter children.

     Professor Art Kramer, who led the study published in the journal Brain Research, said the findings had

important implications for encouraging individuals to take part in sport from a young age."We knew that

experience and environmental factors and socioeconomic status all impact brain development," he said.

"If you get some terrible genes from your parents, you can't really fix that, and it's not easy to do something

about your economic status.But here's something that we can do something about."

1.If you want to improve your children's result in school, ____________.

A.it is worse to ensure that they do plenty of exercise

B.you can have their brain scanned

C.it could be better to make sure that they do a lot of exercise

D.you can do a lot except ensuring that they do exercise

2.According to the passage, which of the following statements is NOT true?

A.The fitness level of the children is linked to their intelligence.

B.Children who have a larger hippocampus will probably have better memories.

C.You can do something about the genes from your parents.

D.Unhealthy children will probably have a smaller hippocampus than others

3.All the following factors that have some influence on one's brain are mentioned EXCEPT

____________.

A.genetic factor    

B.economic status  

C.physical fitness  

D.economic development