Unit 1: Cells and Proteins 2 Flashcards
Signal Transduction occurs when extracellular messages are
hydrophillic
Signal Transduction transduces messages of
hydrophillic molecules
There are three systems of signal transduction:
- Ion channel coupled receptors
- G-protein coupled receptros
- Enzymes coupled receptors
Ligand Gated ion channels: Vesicles contaning neurotransmitter do what?
Fuse with membrane
Ligand Gated Ion channels: Neurotransmitter cross synapse and binds to
receptor channel protein causing it to open
Ligand Gated Ion channels: Now the channels are open what molecules flows in and depolarises the membrane?
Na+
Ligand Gated Ion channels: Depolarisation of the membrane triggers what to open?
more local voltage gated channels to open, allowing in even more Na+
Ligand Gated Ion channels: Allowing in lots of Na+ creates a what?
Action potential across the plasma membrane
G-Protein coupled signalling regulated ion channels: Receptor becomes active due to binding and activates what?
G-protein molecule
G-Protein coupled signalling regulated ion channels: Activated G-protein moves to activate
the potassium ion channel
G-Protein coupled signalling regulated ion channels: Now the channel is open, potassium flows
out down its electrochemical gradient
G-Protein coupled signalling regulated ion channels: Acetylcholine can reduce ______ activity
muscle
G-Protein coupled signalling regulated ion channels: Releasing potassium balances out ____ being released into the cytoplasm.
Na+
G-Protein coupled signalling regulated ion channels: The release of the K+ balancing out Na+ makes it difficult for the membrane to
depolarise triggering cell contraction.
G-Protein coupled signalling regulated ion channels: Acetylcholine binds to
inactive receptor
G-Protein coupled signal Transduction: Ligand such as adrenaline binds to
g-protein
G-Protein coupled signal Transduction: After binding of ligand, what is released by the g-protein?
An alpha subunit
G-Protein coupled signal Transduction: The alpha subunit binds to
Adenylyl Cyclase
G-Protein coupled signal Transduction: Binding of the alpha subunit to adenlyl cyclase causes
adenlyl cylcase to change from inactive to active
G-Protein coupled signal Transduction: Active Adenlyl cylcase now converts ATP to
cAMP
G-Protein coupled signal Transduction: cAMP attaches to what?
The regulatory section of the protein kinase
G-Protein coupled signal Transduction: cAMP binding to the regulatory portion of protein kinase causes the kinase to
split, and ATP bind to the catalytic sections
G-Protein coupled signal Transduction: The ATP/kinase molecules now bind to
phosphorylase which uses up the ATP to break up glucose chains
G-Protein coupled signal Transduction: cAMP is destroyed by
cAMP phosphodiesterase
G-proteins G12 & G13 promote
actin-myosin contraction resulting in cytoskeletal remodelling.
G-protein G1 is involved with
actin fibre polymerisation and membrane protrusion
G1 protein pathway: Step 1 - G1 receptor stimulated. Then the _____ pathway is stimulated
RAC
G1 protein pathway: Once RAC pathway is stimulated, what molecule is produced?
Phosphatidyl inositol triphosphate (PIP3) produced.
G1 protein pathway: Production of PIP3 results in
induced polymerisation of actin filaments and extrusion of the cell towards the stimulus
G12 and G13 protein pathway: G12 & G13 protein receptor is stimulated which causes the stimulation of what pathway ?
RHO pathway.
RHO and RAC pathways are
antagonistic
Olfactory Sensitivity: G-protein coupled receptors are sensitive to
odours
Enzyme-coupled signalling: Binding of a ligand stimulates a
transmembrane enzyme directly
The transmembrane receptor binds to the ligand undergoing a conformation change thus
activating the inactive enzyme
Enzyme-coupled Signalling Case Study: Receptor Tyrosine Kinases, ligand stimulates ___________ of tyrosine amino acids
auto-phosphorylation
Enzyme-coupled Signalling Case Study: Ligands stimulate autophophorylation of tyrosine amino acids by activation of their
catalytic site
Enzyme-coupled Signalling Case Study: Insulin, binds to the receptor activating tyrosine kinase begining a cascade of four intracellular messages:
- Glut-4 transporter to plasma membrane and influx of glucose
- glycogen synthesis
- Glycolysis
- Fatty acid synthesis
Enzyme-coupled Signalling Case Study: Cell Growth Factors stimulate cell
proliferation and growth
Genes that encode cell growth factor and their receptors are mainly what type of cell?
Proto-oncogenes
Oncogenes promote
uncontrolled cell division
Proto-oncogenes promote
cell proliferation and growth
Epidermal growth factor (EGFR) is coded for by
proto-oncogene
The receptor of epidermal growth factor is an
receptor tyrosine kinase
One effect of epidermal growth factor is stimulation of
the transcription and expression of epidermal growth factor
Over expression of epidermal growth factor is linked to
cancer
Some drugs and monoclonal antibodies try to block what receptors?
Receptor Tyrosine Kinases
Herceptin and Erbitux are ?
Monoclonal antibodies
Herceptin and Erbitux block two types of ____ receptor (Her 1 & Her 2) that are over expressed in breast cancer.
Epidermal growth factor
Iressa is a __________ that blocks over expressed EGF receptors in some lung cancer cells
tyrosine kinase inhibitor
Fibroblast Growth Factors are a branch of ligands involved in the control of
cell growth, cell differentiation, vascularisation, wound healing and embryo growth.
Receptor FGFR3 has been associated with bone growth as FGFR3 stimulation …
inhibits the formation of bone from cartilage.
Mutations in FGFR3 have been associated with
achondroplasia the most common form of dwarfism.
Achondroplasia is a condition in which sufferers inherit an allele for
mutated FGFR3 that is overly active
