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28 Cards in this Set

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  • Back
what are the three proteins involved in cell adhesion


1)CAD-1


2) 80 kDa protein


3) discoidin

what is CAD-1


involved in cell adhesion




expressed during cell adhesion - aggregation of ameoba




-cell surface protein


-a type of glycoprotein


-involved in cells sticking together


-not a strong interaction since is a one small, protein

what is the 80kDa adhesion protein


-made by expression of CSA gene


-a complex of proteins called site A


similar to mammalian protein - CAM


-CAM - cell adhesion molecule


-form a tight aggregate


-cAMP turns on its expression

order of proteins expressed in the aggregation of ameoba in the slime mold


1) CAD-1 expressed first allow loose aggregate


2) then when camp binds - CSA gene/CAM is expressed = tighter aggregate


3)discoidin - start of culmination

what is discoidin

the last adhesion protein expressed in distychstelium




allow the multicell organism to adhere to outsite environment




starts to express during culimination (after aggregation)

what is culmination


the stage after aggregation




making the fruiting body

what is discoidin's mammal homologue?


integrin




integrin is used in mammals to attach cells to extracell substances/matrix

what is CF factor


protein that limits how large the slug can get




called the counting factor




determines how many cells can adhere, detects aggregate up to 10,000 cells




inhibits adhesion after this number

why limit the number of cells in an aggregate?

don't want to get to large, hard to maintain, move together
adhesion proteins initiate signal transduction inside the cells

initiate cell stage, specific response
once aggregation finishes what occurs


the slug goes and searches for food




moves as a multicell organism

what is culmination


stage after aggregation




cells differentiate


form fruiting body

what are the conditions that initiate culmination and why


-one factor -PRESENCE OF NH3 ammonia


-ammonia is byproduct of protein metabolism - shows that bacteria are around and being digested by other ameoba




-high ammonia concentration = bacteria present


-low ammonia = not a lot of bacteria present = favors culmination

what is the mechanism behind ammonia concentrations - leading to culmination

ammonia interferes with camp signaling - won't continue culmination process, can even dissociate



how does control of DNA lead to differentiation?


turning on/off genes = expression of genes




leads to differentiation, gives cell its character and function

how does the slug determine which part differentiates into what (spore or stalk)


-has anterior side of slug - leads the way


-posterior end - end of the slug


location of the cells in the slug = determine what it differentiates into




location seems random

which part of the slug differentiates into what (spore or stalk)


-anterior portion becomes prestalk cells


-posterior portion of slug become prespore


-tip of posterior - ALC - anterior like cells are located, part of stalk formation

receptors and signals involved in differentiation


CAR-3 and CAR-4 are camp receptors, have low binding affinity for camp, need high concentrations of camp to react




high concentrations are present in the slug since cells are close together


where are CAR-3 and 4 expressed






CAR-4 in the posterior portion






CAR-3 is expressed in the anterior portion of slug

pathway when CAR-4 binds to camp?

CAR-4 when binds to camp - activates phosphotyrosine phosphatase


- which removes phosphate group from GSKA


-GSKA deactivated - promote spore gene expression

when CAR-3 binds to camp?


CAR-3 binds to camp


activate ZAK-1 a kinase - phosphorylates GSKA


phosphorylated GSKA promotes stalk gene expression

GSKA


the same protein used in turning on or off spore/stalk genes




phosphorylated when CAR-3 active, ZAK-1 active, stalk expression




dephosphorylated when CAR-4 active, spore expression

what does GSKA's homologue do in mammals

also determines cell fate

how are stalk cells further differentiated after GSKA, what are the different stalk cell types


-Dif-1 signal


-PSTO - upper cup of stalk


-PSTA - actual stalk long portion


-PSTAB - lower cup of stalk


-anterior like cells on the posterior end of the slug - make the basal disk of stalk


prespore cells sit on the basal disk

pathway of Dif-1


Dif-1 binds to receptor


signal passes to STAT - signal transduce and activator of transcription


-in dictastelium, STAT actually inhibits transcription

what does Dif-1 STAT do when activated


STAT - turns off PStA genes - forcing them to become PstO




Dif-1 migrates within slug to create differentiation amongst cells

what happens after the stalk cells are differentiated


-ALC cells secrete discoidin to anchor the stalk


-once stalk is formed, spore cells are pushed to the cup at the top of the stalk


-spores in the cup can be spread and released into atmosphere, they are heat and cold reistant, can survive bad conditions

can the cells undifferentiate

no, once ammonia level is too low and camp has bound to receptors, can't go back to being single cells