Module 8
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What is the purpose for cell communication
Survival, divide, differentiate
Explain the different cell signals may be sent
contact-dependent, paracrine, synaptic, endocrine
Describe some general characteristics of cell signalling pathways
extracellular signal will bind to a receptor protein, this send intracellular signaling proteins and then to effector proteins which produce metabolic enzyme, gene regulatory protein, cytoskeletal protein
Define and explain the characteristics of a molecular switch
Signals by phosphorylation, off when phosphate group leaves, uses ATP. Signalling by GTP-Binding, Signals when GTP present, stops when GDP is left
Explain the components of a G protein-coupled receptor signalling pathway, including how the members interact and how the intracellular signal is transmitted
Ligand binding to receptor activates intracellular GTP-binding protein, regulates an enzyme that generates an intracellular second messenger
What is metabolic enzyme for
altered metabolism
What is gene regulartory protein for
altered gene expression
What is cytoskeletal protein for
altered cell shap or movement
What is contact dependent signal
membrane bound signal molecule
What is paracrine signalling
local mediator sent to signalling cell which sends signals to target cells
What is Synaptic signalling
Neuron sending neurotransmitter through axon between the synapse
What is endocrine signalling
Transmit hormone through blood to a receptor of the target cell.
What are the general characteristics of signalling pathways
Specificity(specific binding site), amplification (molecules increase geometrically in an enzyme cascade), modularity(multivalent affinities form diverse signaling complexes from interchangeable parts). reversible points`
Does extracellular signalling molecules usually express fast
Yes, degrade fast as well, signal is transient
Example of signalling effect
Contraction of muscle, decrease rate and force of muscle contraction in heart cells, secretion of salivar in salivary gland
components of a G protein-coupled receptor signalling pathway
inactive receptor, inactive G protein, inactive enzyme
how the members interact and how the intracellular signal is transmitted in G protein coupled receptor
It only activate when GTP is coupled with it, then it will attach it to enzyme which sends another signal
Define a Receptor tyrosine kinase
A receptor is only activate when both domain are bound to phosphate
Explain activation of the insulin receptor and its intracellular signals
insulin receptor activates when insulin is present, transmit ERK to cells needed for cell division
Explain the mechanistic basis of why allosteric enzymes exhibit a sigmoidal substrate dependence.
combination of two michealis-menton curves, same Vmax, different Km values. Equilibrium shifts T to R as substrate binding stabilizes R-state
Describe how stabilization of the T and R state of allosteric enzymes changes their activity
R-state more active, therefore binding to substrate as it converts from T to R. because it was activated by the substrate
Recurring Motifs in Regulation
(1) Compartmentalization–where do the reactions occur? (cytosol, mitochondria, etc.) (2) Allosteric regulation–enzymes catalyzing committed and usually irreversible steps (3) Specialization of organs–we will compare the metabolism of brain, liver, muscle & adipose Hormonal regulation (4) Covalent regulation (5) Enzyme levels
What reaction happens in cytosol
Glycolysis, glycogenolysis, glycogenesis, pentose phosphate pathway(PPP)
What reaction happens in ER?
gluconeogenesis (in cytosol and mitochondria as well)