Signalling Flashcards
What is signalling?
How a single cell responds to environmental changes
How does an extracellular signal affect cells?
the signal will not enter the cell, but it will induce changes within the cell
T or F: different signals will cause different cellular responses
true
What happens to a cell if there’s no incoming signals?
usually apoptosis
T or F: the same signal can cause different effects in different cells
true
What is an example of a signal?
neurotransmitters
hormones
What are the 2 basic ideas of how a cell can be changed?
- fast
2. slow
Describe the fast way to induce intracellular change
This occurs when extracellular signals change proteins that already exist
this results in a fast response
Describe the slow way to induce intracellular change
This occurs when extracellular signals alter gene expression
results in a slow response
What are the 3 basic steps of signalling pathways?
- a signalling cell sends the first messenger (signal ligand) to bind to a receptor on the plasma membrane of a second cell
- on the 2nd cell, a conformational change
sends the signal across the membrane to the cytoplasmic domain - one of two possible routes:
a. cytoplasmic signal cascade
b. a second messenger
What is the first messenger?
a signal ligand
What are the two possible routes that follow a conformational change causing a signal to be transduced across the membrane?
a cytoplasmic signal cascade
a second messenger
What generates the second messenger?
nearby effector enzymes in the cytoplasm
Where can the second messengers be located?
they can stay in the membrane or they can diffuse through the cytoplasm
What does the second messenger usually do?
binds and triggers cytoplasmic signalling (ex. a signal cascade)
What will the cytoplasmic domain of the receptor cause?
a change in a target protein (ex. phosphorylation)
What happens when a target protein changes conformation?
it will change the conformation of another downstream protein (either activating or inactivating it) - this is the signal cascade
the signal cascade will continue until the final protein influences cellular processes
When will the cytoplasmic signal cascade stop?
When the final protein influences cellular processes
What alters the conformations of signalling proteins?
kinases and phosphatases
What is the result of kinase and phosphatase altering the conformation of signalling proteins?
either the inactivation or activation within the cytoplasmic signal cascade
Approximately how many cellular proteins are subject to phosphorylation-dephosphorylation?
~1/3
What does kinase do?
phosphorylates proteins
What does phosphatase do?
dephosphorylates proteins
What are the 2 common types of receptors?
G-Protein-Coupled Receptors (GPCR)
Enzyme-coupled receptors (specifically RTKs)