Intracellular Signalling Flashcards
What do individual cells part of a complex community of interacting tissue respond to?
wide array of extracellular signals
What are 7 signals cells can receive and function?
- Divide - replace cells and for growth
- Growth - grow without div e.g. muscles grow when exercise
- Differentiation
- Movement e.g. migration of immune cells into infected tissue
- Cell Death e.g. once immune cells have fought infection, they die
- Store/mobilise energy – liver, muscles and fat
- Secrete and release - enz
Name 4 types of signal mol
- Hormones and Growth Factors
- Metabolic Regulators
- Neurotransmitters
- Inflammatory Mediators
What is function of hormones and growth factors and e.g.s?
- hormones– stim cell div + growth (development, wound healing)
- e.g. Oestradiol, Testosterone, Growth Hormone,
- growth factors e.g. Epidermal Growth Factor – wound – cells grow + div on skin to repair wound
What is function of metabolic regulators and e.g.s?
- Metabolic Regulators e.g. – Insulin – released in response to glucose – can store energy from meal,
- e.g. Adrenaline – get glucose rapidly in stress situation to respond to stress,
- e.g. Glucagon – releases energy from glucose when u haven’t eaten/starving
What is function of neurotransmitters and e.g.s?
– signals between neurones in brain, neurones and muscles
– Acetylcholine, Glutamate
What is function of inflammatory mediators and e.g.s?
– e.g. Prostaglandins - made at sites of tissue damage/infection - control processes e.g. inflammation, blood flow, formation of blood clots + induction of labour,
- e.g. Cytokines – allow activation of immune cells to fight infection
What are the 4 diff methods for signal action?
- Endocrine
- Paracrine
- Neuronal
- Contact-dependent
How does endocrine signalling action occur?
- endo cell secretes hormone into bloodstream
- travels in blood screen to target cell with receptor
- hormone binds to receptor - response
How does paracrine signalling action occur and e.g.?
- signalling cell releases local mediator to target cells in immediate env
- binds to receptors of local cells surrounding local signal - response
- e.g. infection in lung send signals to immune cells and fight it
How does neuronal signalling action occur?
- neurotransmitter released from axon terminal
- diffuses across gap - binds to receptors on target cell
- have synapse
- signalling with 1 cell in small, localised region
How does contact-dependent signalling action occur and e.g.?
- mem-bound signal mol on signalling cell
- binds to receptor on target cell
- cells acc in contact
- e.g. immune responses – cell signal locally to B/T cell to proliferate and respond to infection
What does binding of signal to a receptor generate?
a biological response within target cell
What are 2 biological responses within target cell from signal binding?
- altered protein syn
- altered protein function
What happens when signal binds to target cell and get altered protein syn and e.g?
- DNA transcribed into RNA
- altered protein syn
- altered cytoplasmic machinery
- altered cell behaviour
- slow (mins to hrs)
- e.g. make more insulin to replace insulin that’s secreted – RNA for insulin gene made and translated to make insulin
What happens when signal binds to target cell and get altered protein function and e.g?
- intracellular signalling pathway
- leads to altered protein function
- altered cytoplasmic machinery
- altered cell behaviour
- fast (
What are 2 factors that make receptors bind to signals and why?
- high selectivity
- high affinity
– to make sure only right signal acts on right cell e.g. just one insulin receptor/cell that can bind to insulin
How can signal be stopped and e.g?
- Receptors have to be turned off (time delay)
- e.g. once glucose levels go back down, need to turn off insulin secretion
What is gen structure of cell surface receptors?
- receptor region
- transmem region
- intracellular region
- N-terminus outside and C-terminus inside cell
Why does hydrophilic signal mol have to bind to cell surface receptor?
- Can’t cross mem as its hydrophobic so cells have to bind to receptor
How do intracellular receptors work?
- small hydrophobic signal mol - e.g. Steroid hormones - Oestradiol, Testosterone can pass directly through mem
- go through mem and bind to receptors inside - stim gene transcription in nucleus
- Long term responses
How are small hydrophobic signal mol transported around body?
Liquid outside and inside cells hydrophilic – need to be carried around in bloodstream by proteins which are hydrophilic
What are 3 major classes of mem receptor?
- Ion Channels
- Enzymatic
- G-protein -coupled receptors (GPCR)
How do ion channels work and e.g?
- Closed then signal e.g. mem pot binds to receptor – changes its conformation - open it
- flow of ions across membrane changes membrane potential
- e.g. Nicotinic acetycholine receptor – binds to Ach – found on muscles and neurones
How is type of enzymatic receptor and e.g?
- protein kinases
e. g. EGF receptor (epidermal growth factor)
How do G-protein coupled receptors work and e.g?
– pass on signal to enz but not enz themselves just activate them
- G protein activates enzyme or ion channel
e. g. Adrenaline receptor
How does protein kinase work?
- inactive protein (switched off) and signal put in
- ATP —> ADP + Pi - Use ATP to put phosphate group onto proteins
- Take 3rd phos and put it on protein
- signalling by phos
What are e.g.s of ion channels?
- Na+, K+, Ca2+ – width only allows 1 type of ion to go through.
- Na+ smallest
How does phos
Phos –ve charged ion – produces –ve charged region so might change charge on that area of protein – activate/inactive protein
