题干

根据下面的化学结构式回答问题.

(1)该式中,A表示____ ,B表示____ ,C表示____ .

(2)该式表示____ 化合物,含有____  个肽键.

(3)该化合物由____ 个氨基酸分子失去____ 分子水形成,这种反应叫____ 

(4)该式中的氨基酸种类不同,是由____ 决定的.

(5)若氨基酸的平均相对分子量为90,则蛋白质的相对分子质量约为____ .

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答案(点此获取答案解析)

氨基,肽键,羧基,三肽,2,3,2,脱水缩合,R基,234

同类题5

根据短文理解,选择正确答案。

    Five years ago, David Smith wore an expensive suit to work every day. “I was a clothes addict(有瘾的人),” he jokes. “I used to carry a fresh suit to work with me, so I could change if my clothes got wrinkled(有褶皱的).” Today David wears casual clothes (便装) to the office. He hardly ever wears a necktie. “I am working harder than ever.” David says, “and I need to feel comfortable.”

    More and more companies are allowing their office workers to wear casual clothes to work. In the United States, the change from formal to casual office wear has been gradual. In the early 1990s, many companies allowed their employees to wear casual clothes on Friday. This became known as “casual Friday”. “What started out as an extra one-day-a-week benefit for employees has really become an everyday thing.” said business consultant Maisly Jones.

    Why have so many companies started allowing their employees to wear casual clothes? “One reason is that it's easier for a company to attract new employees if it has a casual dress code.” “A lot of young people don't want to dress up for work,” says Owen Black, the owner of a software company, “so it's hard to hire people if you have a conservative (保守的) dress code.” Another reason is that people seem happier and more productive when they are wearing comfortable clothes. In a study conducted by Levi Company, 85 percent of employers said that they believe that casual dress improves employee morale (心境, 士气). Only 4 percent of employers said that casual dress has a negative influence on productivity. Supporters of casual office wear also argue that a casual dress code helps them save money. “Suits are expensive, if you have to wear one every day,” one person said. “For the same amount of money, you can buy a lot more casual clothes.”