Topic G Flashcards
3 Steps of how a motor neuron passes info to a skeletal muscle cell
1) Signal binds to receptor
2) Signal transduction
3) Change in cell behaviour
4 types of signal response
- preprogrammed response
- one signal triggers several responses
- signals amplified during transduction
- signals integrated during transduction
contact dependent signalling
cells are adjacent
Signal: membrane protein
Example: Apoptosis
paracrine signalling
local cells
Signal: diffusible molecules released locally
Example: Cancer cells
Synaptic signalling
distant cells
Signal: diffusible molecules delivered by cell extension
Example: Neurons
Endocrine signalling
distant cells
Signal: diffusible molecules delivered by circulatory system
Example: Adrenaline, Insulin, Estrogen
4 types of signals
small proteins, small organic molecules, gasses, extracellular vesicles
True/False Nitric Oxide uses diffusion and needs a receptor
False! It does diffuse but does not require a receptor
Cell surface receptors
ion-channel coupled receptors, G-protein coupled receptors, Enzyme coupled receptors
Example of ion-channel coupled receptors
AChR
example of G-protein coupled receptors
Adrenaline receptor
example of Enzyme coupled receptors
insulin receptor
Intracellular receptors and example
steroid hormone receptors, e.g. Estrogen receptor
When do G-coupled receptors activate
when signal arrives
When do G-coupled receptors deavtivate
when signals leave
Kinases
put phosphates onto target proteins
many proteins are regulated by ……
phosphorylation
Kinase inactive ….. target on/off
kinase inactive target off
kinase active …… target active/inactive
kinase active target active
adrenaline
fight or flight response
what releases adrenaline
adrenal gland cells
how is adrenaline released
regulated exocytosis
pathway of releasing adrenaline
adrenaline receptor is activated and activates G protein that produces cyclic AMP from ATP which activates an inhibitor that releases PKA (kinase active) which turns on the target protein
3 responses of adrenaline
a) liver cells break down glycogen
b) heart pacemaker cells increase rate of AP
c) skeletal muscle break down glycogen
Deactivation (2 things happen)
1) removal of adrenaline by diffusion, degradation, and uptake
2) phosphodiesterase breakdown cAMP inside of cells
Medical significance of adrenaline
epipens used to treat severe allergic reactions
3 steps of enzyme coupled receptors
1) signal molecule dimerizes the receptor
2) dimerized receptor phosphorylates itself
3) phosphorylated receptor activates other proteins
importance of glucose
mobile carbohydrates
pancreas function
make digestive enzymes for gut
which cells have the most glucagon receptors
liver cells
alpha islet cells (~1%)
release glucagon proteins that bind to receptors in liver cells when blood glucose concentration is low (leaves through GLUT)
beta islet cells (~1%)
release insulin proteins when blood glucose concentration is high
why is insulin signalling important
insulins signal that blood glucose concentration is high
insulin is a small ___
protein
insulin is released by
regulated exocytosis
2insulin receptors are ___ and ___ attached
permanently and loosely
true or false insulin protein is a tetramer
false, it is a dimer
when insulin binds to the insulin receptor what happens
brings the subunits close enough to phosphorylate each other
responses of insulin (2)
a) fat and muscle cells display insulin receptors
b) import and store glucose (kinase cascade)
insulin ___ glycogen synthase
activates
when glycogen is synthesized _____ breakdown decreases
glycogen
Deactivation
removal of insulin > subunits move apart > phosphatases remove phosphate groups > pinocytosis beings back using GLUT
Diabetes mellitus (type 1 and 2)
inability to regulate blood glucose
1- problem with insulin
2- problem with insulin recpetors
Type 1 Diabetes cause
body’s own immune system kills insulin producing cells
Type 2 Diabetes cause
prolonged overeating leads to “full” fat cells deliberately displaying fewer insulin receptors
treating diabetes
monitoring glucose levels, insulin and healthy diet
steroid molecules (2)
hydrophobic molecules, made from cholesterol
globular proteins
carry steroid hormones in circulatory system
Steroid hormone receptors (2)
intracellular receptors and transcription factors
purpose of estrogen signalling
sex determination of females
Steps of estrogen activation
1) gonads in embryo becomes ovaries or testes
2) synthesis sex hormones and and do meiosis
3) sex hormones travel to other cells
4) sex hormones enter cells
5) activate transcription factors that turn on target genes
sex of xxy
male
SHBG
both estrogen and testosterone use, sex hormone binding globular protein
Medical significance of estrogen
a) birth control to prevent release of oocytes
b) cancer- some cancer cells make too many estrogen receptors
what toxins does coffee contain
caffeine
what toxins do poppies contain
morphine
what toxins do cannbis contain
cannbinoids
what toxins does tobacco contain
nicotine
What does nicotine do? (2)
target AChR on neurons resulting in increased activity in brains pleasure centre
target AChR on adrenal glands
Nicotine is an ____ which ___ these receptors
agonist, activates
what does caffeine do (2)
target PDE in adrenaline pathway as a competitive inhibitor
target adenosine receptors telling the brain its tired
medical use of caffeine
help breathe and boost lung function
morphine source and medical use
natural, fast acting analgesic
heroin source and medical use
synthetic, none
codeine source and medical use
synthetic, slow-acting analgesic (slowly converts into morphine by liver enzymes)
fetanyl source and medical use
synthetic, extremely fast-acting analgesic
Do to treat overdose
naloxone is an antagonist which blocks these receptors
what do cannibinoids target
CB recpetors
THC
increase in euphoria, decrease in pain, strong agonist
CBD
decrease in euphoria, increase in pain, weak antagonist
if there is more THC than CBD
intoxication
Medical uses of cannibis
multiple sclerosis (drug called savitex 1:1 TBC to CBD) sedation on endoscopic procedures
