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Foundation Sciences · Biochemistry

G-Protein Coupled Receptors

⏱️ 45–60 minutes read 📖 Biochemistry

7-transmembrane receptors signalling via Gs/Gi/Gq heterotrimeric G proteins to cAMP, IP3/DAG and Ca²⁺.

📌 Learning Objectives

  • Describe the key principles of g-protein coupled receptors.
  • Explain the clinical relevance of g-protein coupled receptors.
  • Recognise common conditions linked to g-protein coupled receptors in MLA-style scenarios.

📋 Overview

7-transmembrane receptors signalling via Gs/Gi/Gq heterotrimeric G proteins to cAMP, IP3/DAG and Ca²⁺. This topic integrates with pathology, pharmacology and clinical medicine and is frequently tested in UK medical school exams and the MLA.

🔬 Basic Science

7-transmembrane receptors signalling via Gs/Gi/Gq heterotrimeric G proteins to cAMP, IP3/DAG and Ca²⁺. Detailed mechanisms, regulation and molecular interactions underpin both normal physiology and disease.

🏥 Clinical Relevance

Cholera: Gs locked on; pertussis: Gi inhibited; GPCR pharmacology (β-blockers, salbutamol).

🧪 Investigations

Relevant laboratory tests, imaging or histological examination are used as appropriate to the clinical context.

💊 Management

Management is condition-specific; principles include addressing the underlying biochemical/structural derangement, supportive care and targeted therapy where available.

Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.

🎯 MLA High-Yield Notes & Quick Revision ⌄
High-yield topic for the UK MLA — frequently appears in SBA questions linking biochemistry concepts to clinical presentations and management decisions.
Applying biomedical science to clinical practice Diagnosis and investigation Pathophysiology of common conditions
  • 7-transmembrane receptors signalling via Gs/Gi/Gq heterotrimeric G proteins to cAMP, IP3/DAG and Ca²⁺.
⭐ Exam Pearls ⌄
⭐ High Yield
Gs ↑ cAMP (β-adrenergic, glucagon, TSH)
Gi ↓ cAMP (M2, α2, opioid)
Gq → PLC → IP3/DAG (α1, M1/M3, AT1)
Largest target class for drugs
💡 Clinical Pearl
: Cholera: Gs locked on; pertussis: Gi inhibited; GPCR pharmacology (β-blockers, salbutamol).
⚠️ Exam Tip — Common Mistakes
Confusing g-protein coupled receptors with related but distinct mechanisms.
Memorising pathways without linking to clinical disease.
🔑 Key Facts ⌄
Gs ↑ cAMP (β-adrenergic, glucagon, TSH)
Gi ↓ cAMP (M2, α2, opioid)
Gq → PLC → IP3/DAG (α1, M1/M3, AT1)
Largest target class for drugs
📚 References ⌄
  1. BMJ Best Practice
  2. Robbins Basic Pathology
  3. Lippincott Illustrated Reviews: Biochemistry
  4. Wheater's Functional Histology
  5. NICE guidance where applicable.

Further Resources

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