Cell Signalling Flashcards
Why do cells need to communicate?
To govern and modify each other for the benefit of the organism
Important for:
- immune response
- senses
- cell division/reproduction/cell differentiation
- development/growth
- death
What happens when signalling molecule binds to the cell-surface receptor?
When the ligand binds to the cell-surface receptor, the receptor’s intracellular domain changes, setting off a series of signalling events.
Describe the contact-dependent mode of intracellular signalling
Direct-contact between cells
Membrane bound signalling molecules
Describe the paracrine mode of intracellular signalling
Signalling between nearby cells
Occurs between different cell types
1 signalling molecule can communicate with various target cells
Describe the paracrine mode of intracellular signalling
Signalling between nearby cells
Occurs between different cell types
1 signalling cell can communicate with various target cells
Describe the autocrine mode of intracellular signalling
Signalling between nearby cell types Between same cell types or Ligand activates the cell that produces it Target receptors are on the same cell
Describe the synaptic mode of intracellular signalling
Involves nerve cells
Presence of synapse
Neurotransmitters as signalling molecules
Varying signalling distances
Describe the endocrine mode of intracellular signalling
Involve endocrine cells
Hormone as signalling molecule
Blood as medium
Cover long signalling distances
What are the types of signalling molecules?
- Hormones and growth factors
- Neurotransmitters
- Cell surface molecules
- Cytokines
- Pathogen derived
- will be good if you memorise 1 example for each
How do target cells recognize the extracellular signal (ligands)?
By specific binding of ligand to its receptors
What is the function of receptor?
Detect signal and bind to specific ligand
Transduce the signal across the cytoplasmic membrane
Difference between cell-surface receptors and intracellular receptors
Cell-surface receptors:
Water-soluble signalling molecules bind to specific sites on receptor proteins that span the plasma membrane
Intracellular receptors:
Signalling molecule enters the cell and bind to the intracellular receptor protein in the nucleus
What are the 3 types of cell-surface receptors?
Ion-channel linked receptor
G-protein-linked receptor
Enzyme-linked receptor
Describe the 3 types of cell-surface receptors
Ion-channel linked receptor:
Only open upon binding to ligand, channel is not always open
G-protein-linked receptor:
Ligand binds to the receptor, G-protein binds to the receptor, G-protein gets activated, activated G-protein will bind to the enzyme/ion channel (activating it)
Enzyme-linked receptor:
Ligand binds to the receptor (enzyme), activating the catalytic domain
Give 1 example for intracellular receptors (testosterone)
Testosterone (hormone) in extracellular fluid binds to the receptor protein in the cytoplasm, forming a hormone-receptor complex
Hormone-receptor complex is transported into the nucleus
DNA is transcribed into mRNA
mRNA undergoes translocation to form new proteins
What is the function of intracellular signalling molecules?
Relay and amplifying signals
What is the function of second messengers?
Amplify signals that alter cell response by changing its concentration
Characteristics of second messengers
Small molecules and ions
Water-soluble, short-lived
Changes in concentration, leads to rapid alteration in activity of downstream pathway
How is cAMP produced?
Ligand binds to G-protein-linked receptor
G-protein binds to the receptor, becomes activated
Activated G-protein binds to adenyl cyclase, activating the enzyme
Activated adenyl cyclase converts ATP to cAMP
cAMP activates protein kinase A
When cAMP binds to protein kinase A, it alters protein activity
Cellular responses are carried out
How does the body respond to injury?
‘Injured’ cell releases cytokine
Cytokine binds to the cytokine receptor
Expression of selectin on endothelial cell
Recruitment of lymphocytes to the site of injury
