L8 - Cell Communication Flashcards
Describe paracrine signaling
Acts on nearby cells
e.g Growth factors such as fibroblast growth factor (FGF1)
Describe synaptic signaling
A type of paracrine signalling when nerve cells transmit signals
e.g Neurotransmitters such as acetylcholine (ACh)
Describe autocrine signaling
Signals that act on the signaling cell
Describe endocrine signaling
Hormones secreted from endocrine cells travel via circulatory systen to act on target cells
(long distance signaling)
What are the 3 main steps of cell signaling
- Reception
- Transduction
- Response
What receptors are membrane bound?
Receptors for water soluble molecules
e.g GPCR, Receptor tyrosine kinase, LGIC
What receptors are NOT membrane bound?
Can be located in the cytoplasm or inside the nucleus
e.g hormones such as testosterone, estrogen, progesterone, thyroid hormones
Describe the structure of GPCRs
Transmembrane proteins that pass the PM 7 times
Many different ligands and different functions
What are G proteins?
molecular switches that are either on or off depending on whether GDP or GTP is bound
What is a receptor
A molecule or protein that responds to a specific ligand
What is a ligand
A signalling molecule that binds specifically to another protein
What is an ion channel
A membrane protein through which specific ions can travel
Which body system relies heavily on ligand gated ion channels
Nervous system
released neurotransmitters bind as ligands to ion channels on target cells
What are protein kinases
Enzymes that transfer a phosphate group from ATP to another protein, activating this protein
What are phosphatases
Enzymes that dephosphorylate rendering the protein inactive, but recyclable
What amino acids are involved in phosphorylation cascades
Serine (Ser) or Threonine (Thr)
Therefore mutations affecting these residues could be detrimental
What are examples of second messengers
cAMP, IP3, Ca2+ ions
What enzyme is associated with cAMP
Adenylyl cylase which converts ATP to cAMP
What is cAMP
A second messenger that activates downstream proteins e.g Protein kinase A (PKA)
Describe the steps of GPCR signalling involving Ca2+ and IP3
Activated G protein activates phospholipase C which then cleaves PIP2 into DAG and IP3
IP3 diffuses through cytosol and binds to a gated channel in the ER
Calcium ions flow out of ER down concentration gradient, activating other proteins
Why are there so many steps in cell signaling?
Amplifies the response
Provides multiple control points
Allows for specificity of response (temporal and spatial)
Allows for coordination with other pathways
What is phosphodiesterase (PDE)
An enzyme that breaks down cAMP
Caffeine blocks the action of PDE
How does viagra work
Inhibits a specific cGMP-degrading PDE
Describe the steps in the fight or flight response
Adrenal glands releases adrenaline into blood
Adrenaline molecule binds to a receptor on a muscle cell
Relay molecules transmit signal, activating an enzyme
Enzyme breaks down glycogen releasing glucose that fuels the muscles
What is epinephrine
another word for ADRENALINE
How does adrenalin work in terms of cell signaling
Acts through a GPCR, activates cAMP and two protein kinases in a phosphorylation cascade
What is meant by amplification of adrenaline
A single adrenalin molecule can result in many glucose 1-phosphate molecules via many steps of transduction
Where is glycogen stored in the body
Liver and skeletal muscle
What does glycogen break down into
Glucose 1-phosphate
Which is then converted into glucose 6-phosphate for glycolysis
How does COVID-19 work in terms of cell signaling
ACE2 in our respiratory tract is the cellular receptor for the S-protein of the virus
