tRNA是分子最小但含有稀有碱基最多的RNA。tRNA的二级结构由于局部双螺旋的形成而表现为“三叶草”形,故称为“三叶草”结构。其DHU臂中含有二氢尿嘧啶核苷,与氨基酰tRNA合成酶的结合有关。 ()
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酶的辅酶与辅基的生理功用主要是运载氢原子或电子,参与氧化还原反应,运载反应基团,如酰基、氨基、烷基、羧基及一碳单位等,参与基团转移。大部分的辅酶与辅基衍生于维生素。它们是复合酶的活性中心的组成部分。 ()
A. 正确
B. 错误
听力原文:How can I get to the Friendship Hotel?
(7)
A. Where are you?
B. Take Bus No.18.
Can I help you?
听力原文:M: I'd like to have a plane ticket to Paris.
W: May I see your ID card please?
Q: What is the mail doing?
(21)
A. Buying an air ticket.
B. Looking for his ID card.
Checking in at the airport.
The girls didn't like Jo any more after his mother died.
A. Right.
B. Wrong.
C. Doesn't say.