Class is determined by how well written an article is based on completeness, clarity and referencing. Articles typically are slowly improved up the levels until they reach A-Class, at which point they go through a more thorough review process with strict criteria to become Good Articles (GA) and Featured Articles (FA). The quality level is set using the |class= attribute in the {{WPMOLBIO}} template in the article's talk page.

• FA — Among the best articles that Wikipedia has to offer. These articles have been through an extensive review process to meet the highest standards.
• GA — Articles that have been reviewed and meet the good article standards.
• A — Excellent articles of a length suitable for the subject that provide a well-written, reasonably clear and complete description of the topic.
• B — Articles that contain most of the necessary material but have significant gaps, missing elements or references.
• C — Articles that are missing important content, contains irrelevant material, or are poorly referenced.
• Start — Articles that have a meaningful amount of good content, but are still weak in many areas, possibly lacking a key element such as a standard infobox.
• Stub — Articles that are either very short or rough collections of information that will need much work.

Article significance is based loosely on how aware the general population is of the topic, and therefore how likely they are to consult Wikipedia. Importance is set using the |importance= attribute in the {{WPMOLBIO}} template in the article's talk page. You can additionally set the importance to a specific taskforce (details here).

• Top — Subjects that are first closely examined in high school or earlier (bacteria, amino acid), or that receive significant attention in the media (stem cell).
• High — Subjects that are generally examined at university (RNA polymerase) or are briefly mentioned at the high school level (endoplasmic reticulum).
• Mid — Subjects that are examined at later years of university courses (chaperonin, complement system, RuBisCO).
• Low — Obscure subjects that are important to researchers in the specific field (UvrABC endonuclease).