What is the function of exchange in buying and assembling of marketing?

Buying and Assembling in Marketing:

Procurement of raw materials, finished or semi-finished products has gained great significance for the commercial enterprises and modern industrial. The marketing department plays a significant role in purchasing material for finished or production goods for resale. This is the marketing department that will supply the information regarding the requirements and taste of customer.
Purchasing is different by assembling, which means collection of goods already purchased by different sources at a common point. it is also done through marketing department.