Our research papers are not typical "lab reports." In a teaching lab a lab report might be nothing more than answers to a set of questions.
Such an assignment hardly represents the kind of writing you might be doing in your eventual career.
This term is more commonly used in qualitative research, while the term theoretical model usually appears as a tool in quantitative research.
They both refer to the key theories, models and ideas that exist in relation to your chosen topic.
Your papers are to adhere to the form and style required for the Journal of Biological Chemistry, requirements that are shared by many journals in the life sciences.
Specific editorial requirements for submission of a manuscript will always supercede instructions in these general guidelines.
An important thing to remember is to keep your theoretical model logical and concise.
Your model should serve as a road map for you (as well as your readers) to help quickly understand the theoretical underpinnings of your study.
Written and oral communications skills are probably the most universal qualities sought by graduate and professional schools as well as by employers.
You alone are responsible for developing such skills to a high level.