11 Cell Communication Flashcards
List three forms signals that are received by cells take?
They take light, touch, and most commonly, chemical
Define a signal transduction pathway
A series of steps in which a signal is converted to a response
What property do bacterial populations have that allows them to coordinate their activities to maximum efficiency and productivity?
Quorum sensing, the ability of bacteria to monitor the local density of cells. Example is formation of biofilm
List two ways communication by direct contact can take place in the cell
- Cell junctions: signalling mlcls dissolved in the cytosol pass through either gap junctions (animals) or plasmodesmata
- Cell-to-cell recognition: animal cells may interact by interaction between mlcls protruding from their surfaces
Define local regulator; give an example.
A local regulator is a signalling molecule released by the signalling cell that travels short distances; example is a growth factor or neurotransmitter
List two types of local signalling
a) Paracrine signalling - secreting cell acts on numerous nearby cells by discharging local regulators
b) Synaptic signalling - a nerve cell releases neurotransmitter mlcls into synapse (gap bw nerve cells), stimulating it
List one type of long-distance signalling
Endocrine/hormonal signalling
Define hormone. Two examples of hormones that vary greatly by size and type would be:
It is a chemical used by plants and animals for long distance signalling
A gaseous plant hormone, ethylene, that promotes ripening
Insulin, a mammalian hormone that regulates glucose levels
When glycogen & glycogen phosphorylase are mixed in a test tube, is glucose phosphate generated?
No it is not, becuase the generation requires an intact cell with an intact receptor in the membrane and intact signal transduction pathway
Define ligand. What is the effects of ligand binding?
a mlcl that specifically binds to another larger one.
Ligand binding causes a change in shape for the receptor protein, which activates it and enables it to interact with other cellular mlcls.
Give two examples of a plasma membrane receptor. Explain how it works.
A G protein-coupled receptor. The GCPR is integrated in membrane while the G-protein, acting as a switch, is attached loosely to cytoplasmic side.
When the GCPR is activated (by a signalling mlcl attaching to extracellular site) it changes shape and its cytoplasmic side binds to inactive G-p, and GTP displaces GDP
The activated protein then dissociates from the receptor and binds to a membrane enzyme, activating it which then sends a cellulor response.
The G-protein hydorlzes GTP to GDP releasing Pi group, becomes inactive and leaves enzyme
Receptor Tyrosine kinases
What is a G protein?
A protein that binds to the energy-rich GTP, or guanosine triphosphate. When GDP binds to it, it is inactive.
Abnormal functioning of RTKs is associated with:
many types of cancer
What is a kinase?
A kinase is an enzyme that catalyses the transfer of phosphate groups
A tyrosine kinase catalyses the transfer of P groups specifically from ATP to amino acid tyrosine
What is an ligand-gated ion channel?
It is a membrane receptor. The ion channel receptor remains closed until a ligand binds to it on its extracellular side, at which specific ions can flow through it and affect ion concentration of specific ions like Na+ or Ca^2+
