Flashcards in Signal Transduction 1: Introduction To Receptors And Cellular Signalling Deck (42):
Overall process of signal transduction?
Signal to reception via (amplification) to transduction to response
What does the arrival of a signal in a cell need?
To be relayed through the cell (ie transduced)
Two reasons for needing to understand signal transduction?
1. Cellular signalling helps maintain homeostasis (balance) e.g. Hormones
2. Many medicines control cell signalling events via receptors
Examples of medicines that control cellular signalling via G protein-coupled receptors?
What is a hormone an example of?
Extra cellular signal
What does an endocrine signal do?
It's released from a gland and travels through the blood to act upon a distant target organ
Example of an endocrine hormone?
What does an autocrine signal do?
Acts upon the same cell type they are released from
Example of autocrine signalling?
Example of paracrine signals?
Release of acetylcholine at the neurotransmitter junction
What do paracrine signals do?
They're released from cells to act upon adjacent cells
Where can cell to cell signalling occur?
In the immune system
What's an example of plasma membrane-attached proteins?
T-cell activation by proteins on the surface of antigen presenting cells
How do hormones and other extra cellular signals initiate a chain of events in the cell?
By activating receptors
What is a receptor?
A molecule on the surface or within a cell that recognises and bind with specific molecules, producing a special effect in the cell
What does the lock and key analogy explain?
How each hormone has its own specific receptor
What can activate the receptor and trigger intracellular signalling (leading to a response)?
When a hormone or ligand engages with the correct receptor
What do drugs do?
They take advantage of the lock and key mechanism to give highly specific medicines with few side effects
Examples of drugs that take advantage of the lock and key mechanism?
Mimics adrenaline/epinephrine at the b2-adrenoceptor to treat asthma
What does transmitting a message across the cell membrane involve?
A conformational change in the receptor
Can signalling occur without the hormone passing through the membrane?
How does the receptor control hormone activity at the cell surface?
By acting as a gate keeper of cellular activity
What relays signals from receptors to target molecules in the cell?
Cascades of molecular interactions
How many steps does signal transduction involve?
What can greatly amplify a signal?
Multiple pathways as it provides more opportunities for co-ordination and regulation of the cellular response
Two common mechanisms of signal transduction?
What are second messengers?
Chemical signals that aren't embedded in the membrane and can diffuse in the cell to pass on the message
(Aka they are intracellular molecules that change in concentration in response to environmental signals)
What conveys a message regarding second messengers?
The change in concentration
What is the hormone/ligand that activates the receptor sometimes called?
A first messenger
Can multiple receptors use the same common second messengers?
What are second messengers?
Molecules (chemical signals) inside cells that act to transmit signals from a receptor to a target ie they are free to move in the cell- not attached to the membrane
Why can common second messengers create different responses?
Because of other elements of specificity of cell signalling and coordination of the response
What do different cells have?
A different collection of proteins which allow cells to detect and respond to different signals- pathway branching and "cross talk" can further help the cell co-ordinate incoming signals
What turns protein activity on/off or up/down as required, like a switch?
Phosphorylation and dephosphorylation
What does protein kinase do?
Transfers phosphate from ATP to protein (phosphorylation)
What are many relay proteins in signal transduction pathways?
Protein kinase, which create a phosphorylation cascade
What three amino acids are phosphorylated?
What removes the phosphates from proteins (dephosphorylation)?
What is amplification?
At each step, the number of activated products is much greater than in the preceding step, which means only a very small amount of the initial hormone is needed, and few receptors activated, to produce a response
What is a response function of surface receptors?
Changes in chemicals result in the activation or inhibition of proteins (eg pumps, enzymes, gene transcription factors that directly control processes such as nerve transmission and metabolic pathways)
What is the termination of the signal function of the cell surface receptors?
After the cell has completed its response to a signal, the process must be terminated so that the cell can respond again to new signals (signalling processes that fail to terminate can have highly undesirable consequences)