11 Cell Communication Flashcards
How do bacteria measure the number of bacteria surrounding it?
Each bacteria cell secretes a certain chemical. Therefore the concentration of this can be used by each bacterium to work out its density.
This is known as ‘quorum sensing’
How does ‘quorum sensing’ affect bacterial behaviour?
If they sense that they are in a high density area they begin to secrete substances so that a biofilm is formed.
What are the types of cell singling?
Communication by direct contact, local signalling and long-distance signalling.
What are the forms of direct signalling?
Cell junctions and cell-cell recognition
What is cell junction chemical messaging?
Chemical molecules are passed through the gap junctions/plasmodesmata of neighbouring cells
What is cell-cell recognition?
One cell has molecules on the outside of its plasma membrane that can be detected by receptors on the other cell’s plasma membrane.
What are the forms of local signalling?
Paracrine signalling and synaptic signalling
What is paracrine signalling?
A cell secretes a ‘local regulator’ i.e. a growth factor into the extracellular fluid which acts on neighbouring cells.
What is synaptic signalling?
The axon of a nerve cell secretes neurotransmitters which cross the synapse and trigger the continuation of an action potential.
What are the forms of long-distance signalling?
Endocrine (hormonal signalling)
What is Endocrine signalling?
Specialised endocrine cells secrete hormones into the body fluids i.e. blood which circulate and act on specific cell.
How do hormones act on specific cells?
Only certain cells have receptors for that specific hormone and thus only those respond.
How does long distance signalling occur in plants?
They also have hormones although they are often called ‘plant growth regulators’.
These either travel through vascular bundles, between cells through plasmodesmata or diffuse through the organism as a gas.
What is a common plant gas hormone?
Ethylene (C2H4)
What does epinephrine trigger?
The breakdown of glycogen in the liver.
How does the breakdown of glycogen provide energy?
It is broken down into glucose 1-phosphate which the cells convert to glucose 6-phosphate which is used as an early intermediate of glycolysis
What enzyme breaks down glycogen?
Glycogen phosphorylase
What are the basic steps of responding to a chemical messenger?
1) Reception
2) Transduction
3) Response
How does reception typically occur during chemical messenger?
A receptor, typically on the plasma membrane, binds to the ligand and is activated.
How does transduction typically occur during chemical messenger?
The receptor releases a relay molecule which triggers another receptor which intern releases another relay molecule and so on.
This is known as a ‘signal transduction pathway’
How does response typically occur during chemical messenger?
The final receptor in the signal transaction pathway releases a chemical that triggers an enzyme etc. to perform the intended action or the transcription of specific genes
How does ligand binding generally trigger a response?
It changes the shape of the receptor, causing something to happen.
What is a ligand?
The chemical that triggers a specific receptor.
What type of signalling molecules tends to bind to cell surface receptors?
Water soluble ones as they can not easily cross the plasma membrane as they are hydrophilic