Protein is termed the building block of the body. It is called this because protein is vital in the maintenance of body tissue, including development and repair. Hair, skin, eyes, muscles and organs are all made from protein.
In business, the term word sourcing refers to a number of procurement practices, aimed at finding, evaluating and engaging suppliers for acquiring goods and services 1  : Outsourcing, the process of contracting a business function to someone else. Tradegood sourcing, a process of finding the right suppliers who have gone through the unique Tradegood Business done right verification process, as a leading in quality and safety company. 2  Sourcing (personnel) , the practice of recruiting talent using strategic search techniques.
It depends on companies/industries but I'll try to answer based on my own understanding/experience. - sourcing = search for new sources of supply, place the orders and that's it. - merchandising = it's a term in retail industry, you find products that make good sales (you're in charge of overall profitability of your own product category). In fashion/cosmetics industry, you also have to monitor trends, develop new product ideas and manage product launch. - purchasing/buyer = kind of clerical job, deal with regular suppliers, negotiate, raise the orders.