题干

生物体的生命活动都有共同的物质基础,图示中a、b为有机小分子物质,甲、乙、丙代表有机大分子物质。已知核糖体是由RNA和蛋白质构成的。相关叙述正确的是

A:在人体细胞内,a共有5种

B:b在细胞核中经缩合反应合成丙

C:连接两个b之间的化学键是肽键

D:在某人的神经细胞和肝细胞中,甲一般不同,丙一般相同

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C

同类题2

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    Captain(船长)Nemo invited me and my friends to go hunting with him in the forests of Crespo Island. I asked him why he was so interested in Crespo Island. “I thought you preferred the sea to being on land.”

    “I do,” replied the captain. “But these forests are under the sea.”

After going through a door, we were about ten meters under the water. The light from the sun reached us. Everything looked very colourful. We were going deeper and deeper. At 100 meters deep, we could see quite well, and Captain Nemo stopped and pointed to some dark shapes. This was the forest. The “trees” in the forest were giant seaweed, and all their “branches” were vertical(垂直的).We could not stop looking at them. Fish swam around the branches like birds in a forest.

    Suddenly, I saw a large sea spider about a meter tall. It was going to attack me. Captain Nemo's man killed it with his gun, but it reminded me that the sea could be as dangerous as it was beautiful. When we reached 150 meters, it was dark. The sun's light could not reach this depth(深度). We turned our lights. We could see about 20 meters around us. Finally, we found Crespo Island—where a steep rock wall rose in front of us.

    We could go no further, so we walked back toward the Nautilus. Suddenly, Captain Nemo stopped and shot an animal with his gun, it was a beautiful and rare sea otter. At last, we could see the Nautilus. Several large sharks swam over us. Luckily they didn't see us. We re-entered the Nautilus safely. I was tired but amazed by what I had seen.