Lead the reader to your statement of purpose/hypothesis by focusing your literature review from the more general context (the big picture e.g., hormonal modulation of behaviors) to the more specific topic of interest to you (e.g., role/effects of reproductive hormones, especially estrogen, in modulating specific sexual behaviors of mice.)
The proposal encompasses argumentative writing as well as hardcore research. It will usually contain reviews of various books which support the thesis or hypothesis that it proposes to prove.
How to Write a Psychology Research Paper - Verywell
For example, if you were studying a membrane-bound transport channel and you discovered a new bit of information about its mechanism, you might present a diagram showing how your findings helps to explain the channel's mechanism.