Module 7 Intercellular Communication Flashcards
Why is cellular communication important?
Because cellular functions that are vital for life are regulated by other cells, thus producing a physiological response.
What happens if cellular communication is disrupted?
A break in homeostasis
Intercellular Communication occurs via: (2)
- Direct contact (eg. Gap junctions)
- Chemical messengers (eg. Hormones)
What are integrins?
Transmembrane proteins that help in Intercellular packaging
List the 3 membrane junctions
- Desmosomes
- Tight junctions
- Gap junctions
What are the functions of each membrane junction?
Desmosome: Holds together cells by thin linker proteins (cadherins)
Tight junction: Prevents molecules from passing through (impermeable)
Gap junction: Allows small substances to pass through by hollow cylinders called connexons
Give an example of the role of tight junctions in brain function
Blood-Brain Barrier
(Endothelial cells of the capillaries in the brain are attached firmly together, unlike other capillaries in the body) this is to shield brain tissues from toxins.
What are the 5 basic components involved in Intercellular Communication?
1- Secretory cells 2- Communicating cells (ligands) 3- Specific receptors 4- Signal transduction process 5- Signal response
What are paracrine agents?
Messenger molecules that act on neighbouring cells (eg. Neurotransmitters, histamine)
What are autocrine cells?
Cells that releases a signal molecule on itself
What are endocrine cells?
Cells that releases a signal molecule to blood vessels that will carry it to target cells.
What are the 4 types of chemicals that can serve as extracellular signalling molecules?
- Amines (eg. Epinephrine)
- Peptides (eg. Insulin)
- Steroids (eg. Aldosterone)
- Other small molecules (eg. AA)
What does the magnitude of target cells depend on?
- Concentration of messenger
- No. of receptors present on target cell
- Affinity of receptor for messenger
What are the 2 types of receptors?
- Intracellular (Lipid-soluble)
- Plasma membrane (Lipid-insoluble)
What is a signal transduction?
Events occurring after receptor activation
Example of second messengers?
cAMP, IP3, DAG, Ca2+
What are the 6 steps of signalling event?
Recognition, transduction, Transmission, modulation, response, termination
What are the 4 groups of plasma membrane receptors?
- Receptors that function as ion channels (Ionotropic)
- Receptors that function as enzymes
- Receptors that interact with cytoplasmic JAK
- Receptors that interact with G-protein
Ionotropic Receptors can be fast or slow. Describe each.
Fast channels: receptor is part of the channel
Slow channels: receptor couples by G-protein
Examples for plasma membrane Ionotropic receptors
Receptors for Ach, GABA, glycine, serotonin
What are the 2 major enzymes that are involved in receptors that function as enzymes?
- Tyrosine kinase
- Guanylyl cyclase
What are the functions of protein kinases & Guanylyl cyclase?
P.K: Phosphorylase proteins (activating it)
G.C: Catalyses the formation of cGMP
These two act as 2nd messengers to activate signalling events
What is JAK?
It is an Intercellular enzyme that is not a part of the receptor, but resides in the cytoplasm (PK is part of receptor)
Mechanism of action of JAK
A first messenger binds to JAK & changes its confirmation to activate the kinase. This leads to phosphorylation of Tyrosine residues of receptors which, in turn, could phosphorylase many Intercellular proteins.