PHSI2005 Study Guide - Midterm Guide: Protein Kinase C, Cyclic Adenosine Monophosphate, Adenylyl Cyclase
15 May 2018
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Cell signalling
Gap junctions
oA specialized intercellular connection between a multitude of animal cell-types
oDirectly connect cytoplasm of two cells, allows various molecules, ions and
electrical impulses to directly pass through a regulated gate between cells
Contact-dependent signalling
oInteraction between membrane molecules on two cells
Endocrine signalling
oHormones are secreted by endocrine glands or cells into the blood
oOnly target cells with receptors for the hormone respond to the signal
Autocrine/paracrine signalling
oAutocrine molecules act on the same cell types that produced them
oParacrine molecules act on nearby cells/different cell types
Types of membrane receptor
Receptor- channel: ligand binding opens or closes the channel
Receptor – enzyme: ligand binding to a receptor-enzyme activates an intracellular
enzyme
G protein-coupled receptor: ligand binding to a G protein-coupled receptor opens an ion
channel or alters enzyme activity
Integrin receptor: ligand binding to integrin receptors alters the cytoskeleton
Signalling pathways
Ligand receptor transduction of signal information signal amplification (kinases & 2nd
messengers) cell response
GCPRs & Second Messenger Signalling: cAMP
Cyclic adenosine monophosphate (cAMP) is a second messenger important in many biological
processes. cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal
transduction in many different organisms, conveying the cAMP-dependent pathway
1. Signal molecule binds to G-protein coupled receptor (GPCR), which activates the G
protein
2. G protein turns on adenylyl cyclase (an amplifier enzyme)
3. Adenylyl cyclase converts ATP to cyclic AMP
4. cAMP activates protein kinase A
5. Protein kinase A phosphorylates other proteins, leading ultimately to a cellular response
GPCRs & Second messenger signalling: IP3, DAG, Ca2+
Inositol trisphosphate together with diacylglycerol (DAG), is a secondary messenger molecule
used in signal transduction and lipid signalling in biological cells. While DAG stays inside the
membrane, IP3 is soluble and diffuses through the cell.
1. Signal molecule activates receptor & associated G protein
2. G protein activates phospholipase C (PLC), an amplifier enzyme
3. PLC converts membrane phospholipids into diacylglycerol (DAG), which remains in the
membrane, & IP3, which diffuses into the cytoplasm
4. DAG activates protein kinase C (PKC), which phosphorylates proteins
5. IP3 causes release of Ca2+ from organelles, creating a Ca2+ signal
Document Summary
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