问题 单项选择题 A1/A2型题

脂肪酸B氧化的过程是()

A.脱氢→加水→再脱氢→硫解

B.脱氢→再脱氢→加水→硫解

C.脱氢→硫解→再脱氢→加水

D.脱氢→再脱氢→硫解→加水

E.加水→脱氢→再脱氢→硫解

答案

参考答案:A

解析:脂肪酸B氧化的过程:(1)脱氢:在脂酰CoA脱氢酶的催化下,脂酰CoA的α、β碳原子各脱下一氢原子,生成反△烯酰CoA。脱下的2H有FAD接受生成FADH;(2)加水:反△烯酰CoA在△烯酰水化酶的催化下,加水生成L(+)一β一羟脂酰CoA;(3)再脱氢:L(+)一β一羟脂酰CoA在β一羟脂酰CoA脱氢酶催化下,脱下2H生成β一酮脂酰CoA,脱下的2H由NAD接受,生成NADH+H;(4)硫解:β一酮脂酰CoA在β一酮脂酰CoA硫解酶催化下,加CoASH使碳链断裂,生成1分子乙酰CoA和少2个碳原子的脂酰CoA。

阅读理解

When I was a girl of 10, I joined the school cross-country team and practiced twice a week, on the 1,8-km course I'd never really run before and I thought the course would be easy. It was a real shock I ran out of breathe(喘气)within the first few minutes. I never realized how tiring running could be but I didn’t t think about give up.

Over time,I did get a little bit faster. However, I was really slow. In races, I would finish close to last. I'd always have to stop more than once, especially in the longer races, which were 2. 5 to 2. 8 km. After every race, I'd go home and cry. But 1 still didn't stop running, holding onto that picture of crossing the finishingline and finally doing well.  

Then one of my friends joined the team, too. She could run easily and even came in the 18th in a big race! I felt so slow and my confidence(自信) was lower than ever. I became so nervous when I thought of the races that I wanted to give up badly.

Still. I refund to. Finally. 1 realized that the reason I was to nervous was that I was always worried that I wasn't ready for them. So a few weeks before the next 2. 8-km race. I practiced running almost 3 km every day. which helped me improve my pace(步伐).

When the time came for the big race, all that practicing really paid off. I stopped only once and my pace was so much better.

I realized that I’d finally gotten happiness with running. But the funny thing was. It didn't come from doing better, Instead, it came from the fact that I hid tried harder and never given up.

小题1: Before she took the 1.8-km course, the writer________.

A.knew a lot about it

B.wanted to be a great runner

C.practiced running every day

D.never thought running so tired小题2:The writer was nervous about the race because she_______.

A.had to stop to drink water

B.was worried she wasn’t ready

C.run slower than anyone else

D.could find no coach to help her小题3:The underlined phrase "paid off" probably mean “______”.

A.brought good results

B.coat a lot

C.saved much time

D.came to fail小题4:It can be inferred(推断) from the passage that the writer______.

A.got angry with her friend

B.wasn't pleased with herself

C.was a person with a strong mind

D.had no Interest In running

单项选择题