Cys

例句：

1. 1. The protein is made up of 20 different amino acids, including cysteine.
   这个蛋白质由20种不同的氨基酸组成，其中包括半胱氨酸。
2. 2. Cysteine is an essential amino acid that plays a crucial role in the body's immune system.
   半胱氨酸是一种必需的氨基酸，它在人体免疫系统中起着至关重要的作用。
3. 3. In the human body, cysteine is found in various tissues and organs, such as the liver, kidneys, and brain.
   在人体中，半胱氨酸存在于各种组织和器官中，如肝脏、肾脏和大脑。