In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The alanine aminotransferase was elevated to a peak concentration of 1533 U / L and the serum bilirubin reached a peak of 17 . 0 mg / dL .
### Output Text:
The <span class="chemical">alanine</span> aminotransferase was elevated to a peak concentration of 1533 U / L and the serum <span class="chemical">bilirubin</span> reached a peak of 17 . 0 mg / dL . 