Question

Lipid molecules in a cell are synthesized by
(a) Smooth endoplasmic reticulum (b) Golgi apparatus (c) rough endoplasmic reticulum (d) plastids

Answer 1

Lipid molecules in a cell are synthesized by rough endoplasmic reticulum 
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rough endoplasmic reticulum has ribosomes over their surface and they  synthesize proteins  that are very helpful for an organism 

their surface is rough and hence they are called as rough endoplasmic reticulum 

Answer 2

SER is responsible to synthesize lipids