Overview of cell signalling Flashcards
Cells receive signals from the environment beyond the plasma membrane, e.g.
- antigens
- hormones
- neurotransmitters
- light
- touch
- pheromones
Signals are integrated and cause changes in the cell’s composition and function, such as:
- differentiation and antibody production
- growth in size or strength
- cell division
- movement
How do communications between cells occur ?
Electrically or chemically
Electric current passes through ?
Gap junctions
Chemical signals bind to ?
Receptors on target cells and relays information via second messengers to activate effectors in the nucleus or cytoplasm
What may signals act over ?
Short or long distances
Explain the signal acting for Endocrine Signalling, Paracrine Signalling, Neuronal and Contact-dependent ?
- Endocrine signalling: long distance, slow acting
- Paracrine signalling: short distance, relatively fast
- Neuronal: long distance, very fast
- Contact-dependent: short distance, can be slow or fast
What is Signal transduction?
This is the conversion of one type of signal into another
An environmental signal is first received ?
By interaction with a cellular component, most often a cell-surface receptor
The information that the signal has arrived is then converted into ?
- Other chemical forms, or transduced: this is usually a multi-step process
- The signal is often amplified before evoking a response
Feedback pathways regulate?
The entire signalling process
What do ion channels act as?
Receptor, transducer and amplifier in one protein
Ionotropic ion channels are activated by ?
A ligand binding; voltage-operated channels are activated by a change in membrane potential
What is a Receptor ?
- A membrane-bound or soluble protein or protein complex, which exerts a physiological effect (intrinsic effect) after binding its complementary ligand
- Receptors are specific
Membrane-bound receptors are necessary to allow ?
Hydrophilic signalling molecules to transmit their signal across the plasma membrane
What do Many intracellular signalling proteins act as ?
Molecular switches that cycle between “on” and “off” states in response to a signal (i.e. it is reversible - important for terminating a signal)
Protein kinases (enzymes which phosphorylate) are very common, as are G-proteins, which bind ?
GTP/GDP
Note that any enzymatic step, or repeated cycle, will cause?
Amplification of a signal
Signalling complexes form at?
Receptors: these may be a pre-formed complex activated by a signal molecule, or activation of the receptor may trigger recruitment of intracellular signalling molecules
What does this signalling complex enable ?
A localised response
Different intracellular signalling molecules may also be recruited in different contexts via ?
Modular interaction domains: this enables modularity
Intracellular signalling proteins integrate incoming signals via ?
Different receptors: the response depends on the strength and effect of each signal
In this way, the cell can respond to ?
Different demands and sometimes competing requirements
In addition to molecular switches, there are a number of ways signals can be deactivated:
Feedback loops are important here
Adaptation to a sustained signal over time, e.g. by receptor down-regulation, can lead to ?
Issues like drug tolerance and insulin resistance
Inappropriate activation of signal pathways leads to?
Problems like cancer
