Adrenaline binds to protein receptors causing shape change Steps:

• Adrenaline is a hormone that binds to specific receptors on the cell membrane.
• These receptors are G-protein coupled receptors (GPCRs), which are proteins embedded in the lipid bilayer.
• Binding induces a conformational change in the receptor protein.
• This shape change activates intracellular signaling pathways without the receptor detaching.

Why C is correct:

• GPCRs are transmembrane proteins that change shape upon ligand binding, initiating signal transduction as defined in cell biology.

Why the others are wrong:

• A: Receptors are proteins, not phospholipids; they remain embedded in the membrane.
• B: Receptors are proteins, not phospholipids.
• D: Protein receptors do not leave the membrane; they stay anchored.

Final answer: C