Multicellularity Flashcards
What is multicellularity?
organism consisting of more than one cell
Rank most to least how many times plants, fungi and animals evolved multicellularity
plants = 6
fungi = 3
animal/metazoa = 1
Is fungi more related to plants or animals
animals
What is the closest living relative to metazoan that is single cellular organism?
choanoflagellates
Describe the structure of choanoflaggelates and what is used for double antibody immunofluorescence?
flagella (tubular) and collar (actin)
What is a choanoflagellate?
Bacteria-eating eukaryote
What do they lose when they form colonies?
collar and flagella
What animal is most related to choanoflagellates?
sponges (choanocytes)
Serine, threonine and tyrosine can be ___
phosphorylated
What is receptor tyrosine kinase?
proteins that span cell membrane and binds to ligands cauding cross phosphoryla;tion of eachother and downstream enzymes
What is cytoplasmic tyrosine kinase?
dont bind ligands and are inside cells not on membranes which phosphorylates tyrosine residue
What is found in choanoflagellates? receptor or cytoplasmic tyrosine kinase?
receptor
Animals and choanoflagellates significantly increase number of ______ in their genomes
receptor tyrosine kinase
Single celled eukaryotes have lots of ____ but not ____
cytoplasmic TK, receptor TK
Describe Src activation in choanoflagellates
Src is active = kinase autophosphorylates itself
CSK phosphorylates tyrosine in the tail and it folds back and shuts down src ( acts as a negative regulator)
What about src activation in animals?
- regulation of negative inhibition didn’t happen csk does phosphorylate but doesn’t lead to inhibition
Are cadherins homolytic or heterolytic
homolytic
Why did choanoflagellate (single celled) have so many cadherin genes?
a way to bind to bacteria so it first evolved not for cell adhesion but for catching their food (bacteria)
Explain what happens in absence of WNT
- frizzled is the receptor, wnt is unbound
- GSK3B phosphorylation casuses B catenin to be degraded
- everything is off (TCF and responsive genes are turned off)
Explain what happens in presence of WNT
- when Wnt binds to frizzled
- pulls GSK3B to receptor and it can not phosphorylate b - catenin
- it accumulates, goes to nucleus and binds TCF
What is the result of Wnt responsive cell?
cell shape changes and cytoskeletal changes
Does choanoflagellates have Wnt?
No
Wnt helps establish axis which give organisms….
symmetry
Wnt establish the primary ______ axis of all animals. mainly expressed at ___ end
anterior posterior, tail/posterior
What is a flask cell?
precursor of nerves in sponges
