Where are receptors located ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Receptors**: Receptors are specialized proteins that play a vital role in cellular communication. They interact with various signaling molecules, such as hormones and neurotransmitters, to initiate a response within the cell.

2. **Location of Receptors**: Receptors are primarily located on the outer surface of the cell membrane. This positioning allows them to effectively receive signals from outside the cell.

3. **Structure of Receptors**: The receptors are embedded in the cell membrane in such a way that a part of the receptor, which contains the active site, protrudes outwards. This configuration is essential for them to interact with external signaling molecules.

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