Chap. VI_(Continued) Plasma Membrane_English-2026

II. Functional aspects

• Selective barrier (homeostasis)
• Exchanges (passive, active, vesicular transport)
• Communication (receptors)
• Anchoring (cytoskeleton, extracellular matrix)

III. Permeability function

• Semi-permeable membrane
• Depends on: size, charge, lipid solubility
• Transport types:
  • Passive (diffusion, osmosis)
  • Active (ATP or gradient)
  • Vesicular (endocytosis, exocytosis)

IV. Intercellular communication

Class 1: G protein-coupled receptors (GPCRs)

• 7 TM, G proteins
• Second messengers (cAMP, IP₃, DAG)
• Intermediate response

Class 2: Enzyme-linked receptors (RTKs)

• Enzymatic activity
• Cascades (MAPK, PI3K/AKT)
• Slow response

Class 3: Ionotropic receptors

• Ion channels
• Fast response
• Examples: nAChR, GABA_A