Cell Signalling and Pharmacology Flashcards

Question

activation of a RTK

Answer 1

requires dimerization activates tyrosine kinase kinase phosphorylates on the opposite receptor tail (transphosphorylation) recruitment and binding of adaptor or effector signalling molecules directly to the phosphorylated tyrosine to initiate signalling

Answer 2

the monomeric G protein Ras

Answer 3

glucose transporters GLUT4 stored in cytoplasmic vesicles insulin induced IRS-1 PI-3 kinase/PKB signalling triggers vesicle translocation to the plasma membrane vesicle fuses with membrane where they take up glucose and pass it into the cell

Answer 4

cytokine receptors lack intrinsic activity recruit soluble tyrosine kinase (JAK) ligand binding prolactin causes: receptor dimerization and JAK recruitment and activation JAKs phosphorylate each other and the receptor recruitment of STAT transcription factor to phosphorylated tyrosine residues on the receptor

Answer 5

absence of ligand - found in nucleus presence of ligand - cytoplasmic receptors translocate to the nucleus bind to lipid soluble molecules (steroid hormones) that can pass the lipid bilayer because they are small exert effects by affecting gene transcription structure: ligand binding domain DNA binding domain - to bind to response elements in the promoter region of target genes N terminal region which can be modified by other molecules to enhance transcriptional abilities

Answer 6

auxins - natural indoleacetic acid (IAA), produced in seed embryo, meristems of apical buds and young leaves, stem elongation, root growth and branching, apical dominance, AT from one cell to the next - long distance and local acting - shoot bends to light auxin binds to nuclear receptor which are ubiquitin ligases, binding promotes ubiquitinylation and degradation of repressor protein, suppression of gene transcription is relieved ethylene - fruit ripening, leaf abscission, pass through cell walls or diffuse through air, ethylene receptors are found in the golgi and ER, absence of ethylene, the ethylene receptor is activating a kinase promoting the destruction of the transcription regulator, deactivation of the ethylene receptor allows the transcription of ethylene sensitive genes

Answer 7

extracellular communication in plants is designated by the distance travelled by the signalling molecule to reach its target cell (the signalling pathways are the same too) AT via transport proteins passive process

Answer 8

rely on removing transcriptional repression to allow gene transcription

Answer 9

endocrine system via vascular system which is long distance and slow paracrine system is most common same cell is autocrine juxtacrine is via the plasmodesmata

Answer 10

red light and far red light intracellular receptor two subunits - light detecting pigment or chromophore, region that has kinase activity, exists between two states Pr and Pfr depending on the proportions of red light and far-red light Pfr can modulate gene transcription, translocating to the nucleus either directly binding to and activating a transcription factor or indirectly by phosphorylating transcription factors

Answer 11

blue light - cell surface receptor phytochromes 9 red and far red light which are intracellular receptors

Answer 12

essential for animal development maintains homeostasis in organisms elimination of specific cells that are damaged beyond repair - DNA damage, accumulation of misfolded proteins, cells infected by certain viral agents

Answer 13

note: these changes are irreversible once apoptosis is triggered cell shrinkage chromatin condenses fragmentation of intracellular contents and membrane blebbing formation of apoptotic bodies (membrane bound portions of cytoplasm and organelles) phagocytic ingestion of Abs and degradation

Answer 14

cysteine at active site cleaves target proteins at specific aspartic acids synthesised as inactive procaspase activated by proteolytic cleavage at own aspartic residues initiator caspases: undergo autocleavage activates other caspases effector caspases: activate other effector caspases after cleavage by initiator caspase cleave cellular proteins nuclear effects seen during apoptosis: hallmark cleavage of chromosomal DNA caspase cleaves a protein that normally blocks endonuclease action: - DNA cleavage by endonucleases cuts DNA into internucleosomal units 180-200bp - apoptotic cells show DNA laddering on electrophoresis

Answer 15

intrinsic pathway: lack of trophic factor induced signalling (growth factor or survival factor withdrawal), cells are prevented from dying by trophic factors, DNA damage by radiation or toxins, protein misfolding (ER stress) survival factor or growth factor signalling suppresses apoptosis by: increasing the transcription and translation of anti-apoptotic molecules signal transduction kinases which are activated by stimulation of trophic receptors, phosphorylate and inactivate pro-apoptotic molecules extrinsic pathway: used by cells of the immune system to kill their targets (cancer cells or pathogen infected cells) initiated by death ligands on/or secreted by the immune cells, binding to their receptors on the target cell activated death receptors result in caspase cascade - different initiator caspases used compared with intrinsic route (procaspase 8 in extrinsic route)

Answer 16

phosphotidylserine (PS) found in inner leaflet of PM some molecules will move to outer leaflet in apoptosis action of caspases activate scramblase (Xkr8) which mediates PS flipping

Answer 17

pro-apoptotic molecules: BAX - both BAX and BAK promote apoptosis by forming channels in the outer mitochondrial membrane to allow cytochrome c release BAK BAD anti-apoptotic molecules: BCL-2 - prevents release of cytochrome c from the mitochondria by blocking action of BAX and BAK BCLXL

Cell Signalling and Pharmacology Flashcards

(41 cards)