问题 单项选择题

细胞内的各种生物膜不仅在结构上相互联系,它们的化学组成也大致相同,主要是由蛋白质,脂类和少量的糖类组成。但不同的膜其化学组成上又存在差异,(如下表)这种差异说明了()

A.各种膜起源不同

B.各种膜功能不同

C.膜面积大小不同

D.膜存在的时间长短不同

答案

参考答案:B

解析:生物膜主要由脂质和蛋白质组成,还有少量的糖类。根据题意和图表分析可知:它们的化学组成也大致相同,说明各种膜起源相同;但含量上存在差异,说明各种膜功能不同。从表中无法判断不同结构膜面积的大小和膜存在的时间长短,所以选B。考点:细胞膜的组成和结构点评:本题难度一般,要求学生识记细胞膜的组成和结构的相关知识,考查学生对各种生物膜的组成和结构的理解。

阅读理解

阅读理解。

      The human body is a living machine, and, like all machines, it needs "fuel" to supply it with energy. This is

provided by the food we eat. But how much do we need to stay healthy?

      The energy value of food is usually measured in calories (卡). A calorie is the amount of heat required to

raise the temperature of 1 kg of water by 1℃. The number of calories people need per day is different, as the

picture shows. Also, the number of calories you use at any one moment normally depends on the activity you

are in. For example, you need more calories for standing than for sitting, more for running than for walking,

and so on.

      The energy in food is in the form of three kinds of chemical materials-carbohydrate (碳水化合物),

protein (蛋白质) and fat. Carbohydrate provides 3.8 Cal /gm of the energy, protein 4.0 Cal/gm, and fat 8.8

Cal/gm. Each food contains different amounts of these materials, as the round pictures show.

(P= protein    C= carbohydrate     F=fat)

1. How many calories are needed to raise the temperature of 5kg of water from 35℃ to 90℃? [ ]

A. 55.

B. 175.

C. 325.

D. 275.

2. Which of the following contains the most amount of calories? [ ]

A. Milk.

B. Rice.

C. Peanuts.

D. Milk or peanuts.

3. Who needs the most amount of calories each day? [ ]

A. A woman.

B. An office worker.

C. A farmer.

D. A boy aged 16.

4. Which of following is True?   [ ]

A. You need more calories for swimming than for mountain climbing.

B. A child aged 8 needs the same amount of calories every day as a man over 70 does.

C. A woman feeding baby needs over 4 times the amount of calories that a baby does.

D. Everyone needs the same amount of calories per day.

5. This passage mainly tells us ______. [ ]

A. all the energy is in food

B. the human body needs energy

C. the number of calories depends on your activity

D. we must only eat peanuts to get calories

单项选择题