问题 单项选择题

线粒体内产生的乙酰CoA通过何种途径进入胞液参与脂酸合成()

A.自由透过线粒体内膜

B.乳酸循环

C.柠檬酸-丙酮酸循环

D.苹果酸穿梭

答案

参考答案:C

解析:

①脂酸的合成原料为乙酰CoA、ATP、NADPH、(CO2)、Mn2+和生物素(辅基)。位于线粒体内的乙酰CoA.不能自由透过线粒体内膜,只有通过柠檬酸-丙酮酸循环才能进入胞液,然后进行脂酸合成。每经过1次柠檬酸-丙酮酸循环,可使1分子乙酰CoA由线粒体进入胞液,同时消耗2ATP,还为机体提供NADPH以补充合成脂酸的需求。②乳酸循环也称Cori循环,是避免体内乳酸大量堆积的重要途径。③苹果酸-天冬氨酸穿梭是肝和心肌胞浆中的NADH进入线粒体内的机制。

单项选择题

After winning a big game, athletes are often asked how they feel. Usually athletes say how (1) it is to win this big game. On the contrary, the fact is that losing a big game, or in my case, all the games, can be even harder.

From the spectators’ point of view, last year’s basketball (2) for my high school team was nothing (3) of an embarrassment. And (4) 0 and 20 is certainly nothing to be proud of, that season had a bigger impact on me than any other. As a team captain, I knew it probably wouldn’t be the (5) year, but did I ever think we would lose every game Of course not. Since six of our top players had graduated, it was clear that we were a (n) (6) team who would struggle. The struggle began earlier than expected, (7) , as our team center was suspended (禁赛) for the season, and two key members decided to (8) for some reason. At this point, dropping out probably passed through every player’s mind, but in the end, we all stuck if out, (9) to work still harder.

Then there came a time when even our (10) and given up on us. Personally, I felt like it was (11) worthwhile giving my all. I thought, if even the coach doesn’t believe in us, why should I But just as my hope began to (12) , a teammate called a meeting. He said," Nobody thinks we are going to win, but, as teammates and friends, we (13) it to each other to go all out every game. "

It was that moment that (14) me how to be a leader. It hit me that I certainly didn’t (15) the role. As a leader you can never quit (16) the team who looks up to you. It is one (17) to be named captain, feel great and go through the motions, but it is quite another to be a real captain and make sure everyone realizes their full (18) all the time.

I am sure it is great to go through without losing and bringing home awards. But in all honesty, I (19) the fact that my team lost every game last year. It may not help me to become a better basketball player, but it already has made me a better leader, and (20)

17().

A.matter

B.aspect

C.issue

D.thing

单项选择题