Final answer:
SR-B1 is found in the liver and facilitates reverse cholesterol transport by binding to HDL, while SR-A is found on macrophages and is involved in phagocytosis by binding to LDL and other particles.
Step-by-step explanation:
When comparing SR-B1 found in the liver to SR-A found in macrophages, it is crucial to understand their functions and locations. SR-B1, or scavenger receptor class B type 1, is primarily involved with the good cholesterol or high-density lipoprotein (HDL) by binding to it and facilitating reverse cholesterol transport. This means that SR-B1 helps to clear cholesterol from the blood by taking up cholesterol from HDL and delivering it to liver cells. Conversely, SR-A, or scavenger receptor class A, is found on macrophages and is involved in their immune functions like binding to and ingesting various forms of low-density lipoproteins (LDL), often referred to as 'bad' cholesterol, as well as other particles through phagocytosis.