Huang Wen Ying

黄文英

Institute of Physiology

Physical education school of JXNU

Email: wenying@jxnu.edu.cn

Chapter 1

THE CELL AND TIS REGULATORY MECHANISMS

1.Structure and function of the cell1.2 nucleus

The nucleus is the headquarters of the cell. It regulates all cell activity. It consists of a nuclear envelope (the outer membrane) and nucleoplasm （核质） . In the nucleoplasm you can see chromatin （染色质） and the nucleolus （核仁） .

nucleus

The nuclear envelope is a double membrane. Is has 4 phospholipid layers. It is also has large pores through which materials pass back and forth.

Within the nucleus are found chromatin and a structure called the nucleolus. Chromatin is DNA in its active ( 活性 )form. It consists of DNA looped around histone （组蛋白） proteins. The nucleolus is a knot（结） of chromatin. It is the nucleolus that manufactures ribosomes （核糖体）

The nucleus regulates all cell activity. It does this by controlling the enzymes present. The chromatin is composed of DNA. DNA contains the information for the production of proteins. This information is encoded in the 4 DNA bases. Adenine( 腺嘌呤） , guanine （鸟嘌呤） , cytosine （胞嘧啶） , and thymine（胸腺嘧啶） . The specific sequence of these bases tells the cell what order to put the amino acids.

There are three processes that enable the cell to manufacture protein: Replication allows the nucleus to make exact copies of its DNA Transcription allows the cell to make RNA working copies of its DNA In translation the Messenger RNA is used to line up amino acids into a protein molecule

DNA