Cell signaling Flashcards
Why do cells communicate which each other?
To coordinate the activities of the organism as a whole. To induce change in cell behaviour: movement of cytoskeleton, activation of specific genes in
nucleus, cell growth, anabolic or catabolic rearrangement of molecules,
What is the main mechanism of cell signalling? List its basic components involved in this
process.
Reception (ligand bind to receptor)
Transduction (cascade, a series of internal reactions where other chemicals, called second messengers, help amplify and transmit the signal to the DNA of the cell)
Response
What is the difference between endocrine and paracrine cell signalling?
Endocrine - further away
Paracrine - signals to neighbour cells
What is a typical property of a slow cell response?
Altered protein synthesis. Change in gene expression! Cell
differentiation, increased cell growth,
cell division
What are the differences in a ligand that binds on an extracellular receptor and a ligand that
binds on an intracellular receptor?
Peptide hormons are water soluble and therefore not able to enter the cell. They bind on receptors that send messages into the cells.
Steroid hormones are lipophilic and can enter the cell membrane and bind to intracellular receptors.
What is GAP?
GTPase-activating protein. GAP’s role is to turn the G protein’s activity off.
How is the G-protein deactivated?
It is inactivated by RGS proteins (for “Regulator of G protein signalling”).
RGS proteins stimulate GTP hydrolysis (creating GDP, thus turning the G protein off).
Describe similarities and differences between ion channel coupled receptors and G-protein
coupled receptors.
Ion channel coupled receptors simpler and more direct than G protein coupled. G protein coupled have a cascade of reactions, second messengers.
Why are ion-channel coupled receptors less complex than GPCR?
Most direct way of cell signaling. Transduction of chemical signal to electrical signal.
Describe the cascade when adenylyl cycle is activated.
produces cyclic AMP which activates protein kinase A. Activate phosphorylase kinase can then phosphorylate and active eg, glycogen breakdown, transcription regulator.
- Describe the cascade when phospholipase C is activated.
Phospholipase C
cleaves an inositol
phospholipid at the
plasma membrane. Acts as a ligand and opens Ca2+ channel. Ca2+ can activate protein kinase C.
How is receptor tyrosine kinase (RTK) deactivated?
Response ending by protein tyrosine phosphatases (removing phosphates on tyrosine of
RTK) or destroyed in lysosomes
Describe the working mechanism of Ras as a signalling protein.
RAS is a GTP-binding protein. Mutations in RAS most common oncogen. Part of the switching on and off the signals.
- Why is a mutation in RAS and RAS-signalling proteins linked to cancer?
Mutated RAS* is stuck in the active state, ignores signals to the contrary, and drives cells to become cancerous.
What happens when signaling pathways are not terminated properly?
There is nolonger any signal. Constantly activated.
- What is meant by “cross-talk” within cell communication?
Cross-talk between different pathways. Cell has to deal with several signals and react to this combination.
