Cell signalling Flashcards
What is signal transduction?
The conversion of extracellular signalling molecules (biotic e.g. hormones/growth factors OR abiotic e.g. temperature, pH) into a form inside the cell that can be interpreted and acted on
What does the survival of a multicellular organism depend on?
The ability to determine position and function within an organism as achieved through social control where cells signal their status to other cells
Cancer
A defect in signal transduction processes that control growth differentiation and proliferation
What is quorum sensing?
A process where non-virulent bacteria signal to each other to establish a virulent response
Is cell signalling in prokaryotes well understood?
No, particularly the range and types of biomolecules that are used to permit communication between organisms in an active microbial community
Is cell signalling in lower eukaryotes well understood?
Better understood
3’,5’-cyclic adenosine monophosphate in the starvation response of the social amoeba. cAMP produced so amoeba can form a stalk and explode to distribute themselves.
Pseudomonos aeruginase
Bacteria that produce quorum sensing molecules and when these reach a sufficiently high concentration a virulence response is switched on to form a biofilm that enables the bacteria to adhere to surfaces and grow resistant bacterial colonies.
How can cells communicate?
An extracellular signalling molecule can be released from another cell through exocytosis. This can then diffuse through the plasma membrane of another cell.
What signalling is used n the development of the mammalian organ system?
Notch and Notch ligand signalling
Describe Notch and Notch ligand signalling
An extracellular signal molecule binds to a receptor to activate a signal transduction cascade.
Intracellular signalling proteins
Target proteins
Response: altered metabolism, altered gene expression, altered cell shape or movement
What type of receptors do extracellular signalling molecules bind?
Specific receptors
What is the receptor for adrenaline?
Beta-adrenergic receptor
Describe cell surface receptors
Hydrophilic molecules that transduce information across a membrane
Describe intracellular receptors
Ligands with the capacity to cross a plasma membrane. Hydrophobic signalling molecules associated with a carrier molecules
What are the 4 broad types of intracellular signalling?
Endocrine
Paracrine
Autocrine
Signalling by plasma membrane attached proteins
Endocrine
Co-ordinates cell behaviour over long distances
Specialised cells secrete ligands into the bloodstream to be distributed around the body
Slow
Paracrine
Acts over small distances
Diffusion of ligand is limited by extracellular matrix and enzymes
Occurs when a signalling molecule is produced by exocytosis
Autocrine
Cell produces a ligand that binds to its own receptors to reinforce a biological response
This mechanism is strongest among cells that enable a group to enter a specific developmental pathway
Provide an example of autocrine signalling
Eicosenoids are fatty acid derivatives that are made by cells in all mammalian tissue. On tissue damage eicosenoid production increases and acts in an autocrine fashion to mediate pain, fever and an inflammatory response
Contact dependence
signalling of integral membrane proteins to adjacent cells
e.g. gastrolation in embryo development to establish polarity
Give 4 examples of what cell signals may result in
Cell proliferation
Cell survival
Programmed cell death
Cell differentiation
How can acetylcholine cause different responses?
Skeletal muscle = contraction
Heart = relaxation
Salivary glands = increased secretion
Which factors determine the response of a cell to a combination of signalling molecules ?
The receptors that the cell possess to detect those signals
The nature of the intracellular machinery by which the cell interprets the signal
Nitric oxide on smooth muscle cells
produced in response to sympathetic nervous stimulation of endothelial cells. NO passes to smooth muscles causing them to relax and blood flow to increase.
Sympathetic nervous system and acetylcholine
The sympathetic nervous system activates a nerve terminal to produce ACh which acts on an endothelial cell lining the blood stream.
NO synthase is activated to produce NO which diffuses across membranes and binds to guanylyl cyclase which converts GTP -> cyclic GMP so smooth muscle cell relaxes and blood pressure decreases
