Cell signalling Flashcards
What is an example of system of communication?
Endocrine system
What does the endocrine system uses to “communicate”?
Release hormones into the bloodstream to facilitate communication
What does hormones initiate?
Chemical signalling
(…when hormones bind to receptors…)
What does the chemical signalling consists of? (vaguely)
- Reception
- Transduction
- Response
What does chemical signalling bring about?
Homeostasis
What is homeostasis?
The maintenance of a constant internal environment.
What is an example of chemical signalling?
Regulation of blood glucose concentration
What is the blood glucose concentration of a healthy person?
800 mg/dm3
What are the main stages of cell signalling?
- Ligand-receptor interaction
- Signal transduction (phosphorylation cascade and signal amplification)
- Cellular response (change in gene expression)
What occurs during ligand-receptor interaction?
(2 steps)
- Ligand has a 3D conformation complementary to the active site of the receptor and binds to it.
- Binding of ligand to receptor forms a ligand-receptor complex, causing receptor protein to undergo a change in 3D conformation.
What affects the location of where the hormone binds to?
Solubility of the hormone
Where are the different locations of hormones binding to the receptors?
- Receptors in cell surface membrane (CSM) - soluble hormone
- Receptors in the cytoplasm or nucleus (Intracellular receptors) - insoluble hormone
What does the activated intracellular receptor do?
The activated receptor acts as transcription factor and binds to control elements in the DNA to regulate transcription and gene expression -> causing a response -
- carries out the complete transduction of the signal
What occurs in the signal transduction stage?
(3 summarised steps)
- A combination of small and large intracellular signalling molecules relay signals received by the receptors at the cell surface into the cell interior.
- The activated receptor activates another protein which then activates another molecule and so on.
- The resulting chain of intracellular signalling events ultimately alters effector proteins and are responsible for modifying the behaviour of the cell.
What are the 2 types of intracellular signalling molecules of a signal-transduction pathways?
- Second messengers
- Relay proteins
What are second messengers and what do they contribute to signal transduction?
- small, non-protein molecules/ions
- they pass signal from the hormone (1 messenger) by binding to and altering 3D conformation of relay and effector proteins
Name an example of second messenger.
Cyclic adenosine monophosphate (cAMP)
How is cAMP produced?
- Binding of a hormone (glucagon) to the receptor (GPLR) … would lead to activation of the enzyme adenyl cyclase.
- Activated adenyl cyclase converts ATP to cAMP.
What is the function of cAMP?
cAMP activates protein kinase which phosphorylates other proteins, giving rise to cellular response.
What are the features of second messengers that benefit/cost them in their functions?
Small :
1. can store large amounts in cell
2. diffuse quickly throughout the cell
Non-polar :
3. will not be degraded by protease in cell
4. not easily affected by change in pH/temp in cell
5. protein synthesis takes a longer time -> unsuitable for rapid action
6. protein synthesis takes alot of energy resources.
What causes degradation of cAMP?
enzyme Phosphodiesterase -> converts cAMP to an inactive product, AMP
What is negative feedback?
