What are the four main methods of cell communication?
- Direct cytoplasmic contact
- Contact-dependent signals
- Diffusible chemical signals
- Neuronal signalling
What is the difference between paracrine and autocrine signalling?
Paracrine signalling: The signal travels a few mm and affects a local cell.
Autocrine signalling: The signal affects the cell it was released from.
What are the characteristics of endocrine signalling?
- Hormone travels through the bloodstream to target cell
- Hormone concentration in the blood is approximately 10^-9 mol/l
- Receptors must have high affinity for the hormone
What are the three types of neuronal signalling?
- Neurotransmitters
- Neurohormones
- Action potentials
What are the four steps of signal transduction?
- Signal molecule binds to receptor
- Receptor protein activates intracellular signalling molecules
- Signalling molecules alter target proteins
- Produces a response
What is signal amplification in cell signalling?
Pathways form a cascade and produce signal amplification, allowing for a small initial signal to result in a larger cellular response.
What are the two main types of receptors in cell signalling?
- Intracellular receptors
- Cell membrane receptors
What are the four types of cell membrane receptors?
- Receptor channels or ionotropic receptors
- G protein-coupled receptors (GPCRs) or metabotropic receptors
- Receptor enzymes or enzyme-linked receptors
- Integrin receptors
Describe the basic mechanism of G protein-coupled receptors (GPCRs).
- Signal molecule binds to receptor
- GDP is exchanged for GTP
- The G protein subunits (alpha, beta, and gamma) separate into α and βγ
GPCRs can also be linked to ion channels
How do receptor enzymes (enzyme-linked receptors) function?
Signal binds to receptor, triggering protein kinases to phosphorylate other enzymes in the pathway.
What are the functions of integrin receptors?
- Interact with the cytoskeleton
- Involved in cell movement
- Involved in cell adhesion
- Involved in platelet aggregation
What response do steroid hormones trigger
Change in transcription
What are the stages in the GPCR-adenylyl cyclase pathway
- G protein activates adenylyl cyclase
- Adenylyl cyclase converts ATP > cAMP
- cAMP = PKA
- PKA phosphorylates target proteins
What are the stages in the GPCR-phospholipase C pathway?
- G protein activates phospholipase C (PLC)
- PLC converts PIP2 into DAG and IP3
3.1 DAG activates PKC
3.2 IP3 releases Ca2+ = activates PKC - PKC phosphorylates target proteins
What are the stages in the NO - GTP pathway
NO—Guanylyl Cyclase—GTP>cGMP
How is cGMP created
GTP + Guanylyl cyclase
How is cAMP created
ATP + Adenylyl cyclase
