I'm trying to prepare biological network pathways and signal transduction. Based on the requirement, please suggest online available tools to draw scientific figures.
ConceptDraw DIAGRAM is a powerful biology drawing software. ConceptDraw DIAGRAM software has samples, templates and libraries containing biological vector symbols, to help you create scientific and educational designs in the field of biology.
I agree with Shambhabi suggested https://smart.servier.com/, which has collection vector files for representing your own ideas in biological figures without any copyright issues for FREE.
I usually use draw.io both offline and online (connected with my Dropbox account). This is a free software. You can draw almost everything from there including infographic, graphical abstract, diagram etc...