Cell Signaling Flashcards
Cell signaling characteristics
Maintaining homeostasis
Needs receptors
Universal, very similar between species
Quorum sensing
Production of molecules which when reached threshold, can activate a social activity
Allows bacterial populations to coordinate their behaviours so they can Cary out activities made by multiple cells (ex mating, releasing toxins, causing diseases (virulence) and forming biofilms)
Ex:
When food is scarce, individual rod-shaped cells will secrète molecule to stimulate aggregation
Aggregation will cause spore to form
Fruiting body will be formed and will survive until environment improves
Junctions vs recognition
Gap junctions are for cells that have to work in synchronisation
Cell to cell recognition
More common
Chemical
The
Hormones
Identical to neurotransmitters but goes through the blood
Secreted and synthesized by endocrine glands (organs)
Travels in blood to target cells
Epinephrine (fight or flight) has its version. It also causes blood glucose to increase
Local signaling
Talking between neighbours cells by releasing chemicals called cytokines int extra cellular fluid to coordinate tissue
Ex growth factors
2 types of hormones
Proteins, hydrophilic, majority, bind to receptors outside and causes signal transduction cascade
Steroid, hydrophobic, bind to receptors inside cell in cytoplasm or nucleus
Types of water soluble signalling molecules receptors
G protein-couple receptors
Receptors tyrosine kinases
Ion channels receptors
Why do we need 2 regulatory system
Endocrine and nervous system
Endocrine system is slower but lasts longer because have to synthesize and release hormones and can take days (ex reproduction)
Nervous system is fast (nervous impulse)
Functions nervous system
Receive sensory input
Integrate input
Respond to stimuli
Nervous tissue
Neurons: cells that transmit nerve impulses
Neuroglial: do not conduct nerve impulses, support and nourish neurons
Structure of neurons
Dendrites (hair up): receive info
Cell body (soma): controls metabolic activity
Axon (long extension): conducts impulse away frl cell body, terminal release chemicals that affect activity of nearby neurons or effector cells
Axon terminal with vesicles of neurotransmitters
Only goes in one direction because of relative refractory period
G protein coupled receptors
Largest family
Cell surface transmembrane receptor
Epinephrine bind to this
Yeats mating
G protein: binds the enerhy rich molecule GTP
G protein receptor gets activated with signallinh molecule
G protein travels to it, phorphorilizes GDP into GTP
travels to inactive enzyme, activates it,
causing a cellular response, then enzyme replaces GTP with GDP
Tyrosine kinase receptors
plasma membrane receptors with enzymatic activity
alpha helix
part of receptor extending into cytoplasme functions as tyrosine kinase, catalses the transper of a phosphate group from ATP to the amino acid tyrosine on a substrace protein
1 receptor may activate ten of more different transduction pathway
signalling molecule (ligand) binds to ligand-binding site on both receptors
they join (dimer), activating tyrosine kinase region (unphosphorylated dimer)
fully activated when phosphorylated (6 ATP to ADP) (phosphorylated dimer)
activated relay protein bind, different can bind to different tyrosime and cause different cellular responses
Ligan gated ions channels
act as a gate when receptor changes shape
when signal molecule binds, gate opens or closes, allowinh or blocking flow of specific ions (Na+, Ca+) throygh the channel
importan in nervous system
