问题 单项选择题

赖氨酸

A.酸性基
B.碱性基
C.芳香基
D.含硫基
下列氨基酸侧链分别属上述何种基团

答案

参考答案:B

解析:[考点] 氨基酸的分类
根据侧链R的结构和性质可将氨基酸分为四类:(1) 非极性R基氨基酸,包括四种带有脂肪烃侧链的氨基酸(丙氨酸、缬氨酸、亮氨酸、异亮氨酸)、两种含芳香环氨基酸(苯丙氨酸、色氨酸)、一种含硫氨基酸(蛋氨酸)和一种亚氨基酸(脯氨酸);(2) 不带电荷的极性R基氨基酸,包括三种具有羟基的氨基酸(丝氨酸、苏氨酸、酪氨酸)、两种具有酰胺基的氨基酸(谷氨酰胺、天冬酰胺)、一种含有巯基氨基酸(半胱氨酸)和R基只有一个氢的甘氨酸;(3) 带正电荷的R基氨基酸,这是一类碱性氨基酸,包括赖氨酸、精氨酸和组氨酸;(4) 带负电荷的R基氨基酸,是一类酸性氨基酸,包括天冬氨酸和谷氨酸,它们都含有两个羧基。根据上述分类,第127题答案为D项,第128题答案为B项。

阅读理解

阅读理解。

Rules of Reading Club

     The following rules will be used for the Reading Club:

     1. All books must be read from page one to the last page.

     2. The parent or the teacher will initial(write the first letter of one's name)the booklist after a student

has finished reading a book. Teachers will initial the booklist only for the books read at school. It is the

responsibility of the student and parent to write the names of all books read, and the number of pages of

the book on the booklist.

     3. All books read must be of the student's reading level or above. For example, a third grade student

should not read first grade books if he or she is able to read at a third grade or higher reading level.

     4. All books the student finishes during the school year (including the textbooks read at school) will be

counted towards the 100 books. Comic books and the like will not be counted. Books of good quality

read from the school library, public library, classroom, home, etc. will be counted.

     5. When a student has finished a club booklist (one sheet of 25 books or 1,500 pages), he or she

should bring the sheet to the office. The child will get a small reward and may get another piece of

booklist to go on reading. It takes four booklist sheets for 100 books or for 1,500 pages to reach 6,000

pages. Either way-You are a winner!

1. The student needs to ask his/her parent or teacher to initial the booklist ________.

A. as soon as he/she begins to read a book

B. before he/she reads a book

C. after he/she finishes reading a book

D. while he/she is reading a book

2. What kind of book will not be counted?

A. Story books.B.Picture books.

C. History books.D.Biology books.

3. How many books should a student read before he/she gets another booklist?

A. 25.

B. 1,500.

C. 6,000.

D. 100.

4. According to the rules, which of the following is NOT true?

A. The student should read the whole book through.

B. The parent will initial the booklist for the books the student reads at home.

C. A third grade student can read the first grade books if he/she likes to do so.

D. The student needs to read 100 books or 6,000 pages in the school year to be a winner.

单项选择题 A2型题