Final answer:
Glycoproteins and glycolipids attached to the outer lipid layer of animal cell membranes play a crucial role in cell-to-cell recognition and interactions with the external environment.
Step-by-step explanation:
Glycoproteins and glycolipids are carbohydrate complexes attached to the outer lipid layer of animal cell membranes. These carbohydrates play a primary role in cell-to-cell recognition. They form specialized sites on the cell surface that allow cells to recognize each other and enable interactions with the external environment. This recognition function is crucial as it allows the immune system to differentiate between self and non-self cells or tissues.