Final - Midterm 3 Flashcards
based on cell activities readily visible in the light microscope, there are two major cell cycle phases:
M phase, interphase
G0 phase
cells that have stopped dividing and are arrested in a stage preceding replication of cytoplasmic contents and organelles
as animal cells enter mitosis, their microtubules disassemble and then reassemble forming the mitotic spindle with a focus at the:
centrosome
what permits the interaction between the cytoplasmically-formed mitotic spindle and the chromosomes to occur
nuclear envelope breakdown
the nuclear lamina is disassembled by:
the depolymerization of the lamin filaments
the assembly and disassembly of intermediate filaments are controlled primarily by:
phosphorylation and dephosphorylation
plectin:
composes the cross-bridges that hold intermediate filaments together
if a cell contains an ATP analog that cannot be hydrolyzed, what will be the consequence to normal actin depolymerization:
there will be no depolymerization
the Arp2/3 complex:
- nucleates new branches of actin off of existing filaments
- nucleates new branches of actin starting with the negative end of a monomer facing the complex
what molecular motor is associated with actin filaments:
myosins
what accounts for the decrease in the length of an entire muscle
the combined decrease in sarcomere length
how does an actin thin filament manage to move continuously during a contraction cycle
all of the myosin heads beat out of synchrony with one another
nebulin:
a protein that is thought to act like a ‘molecular ruler’ by regulating the number of actin monomers that are allowed to assemble into a thin filament
titin:
blocks the myosin binding sites on actin thin filaments in a stimulated sarcomere
ATP binding to myosin in a contraction cycle:
releases myosin from actin
high affinity binding with the signalling molecule allows:
efficient recognition of extracellular signalling molecules by receptors on the responding cell’s surface
where is the guanine nucleotide-binding site of the G protein located?
on the G alpha subunit
what are the events of G protein activation:
- binding of a hormone or neurotransmitter to a G-protein couples receptor
- change in conformation of the cytoplasmic loops of the receptor
- increase in the affinity of the receptor for a G protein on the cytoplasmic surface of the membrane
- G protein binds to activated receptor forming a receptor G-protein complex
- conformational shift in the alpha subunit of the G protein
- release of GDP by the G protein
- binding of GTP by the G protein
in order to begin desensitization, the ____ domain of the activated G protein coupled receptor is phosphorylated by a specific enzyme called a _____
cytoplasmic, G protein coupled receptor kinase
arrestins:
proteins that bind to GPCRs and compete for binding to those GCPRs with heterotrimeric G proteins
how is signalling by an activated G alpha subunit terminated:
the bound GTP is hydrolyzed to GDP
the role of A kinase anchoring protein is:
to confine PKA signalling to specific parts of the cell
receptor mediated dimerization:
ligands act as allosteric regulators that turn on the ability of their receptors to form dimers
once the kinase domain of receptor protein tyrosine kinase has been activated, what does the activated receptor protein tyrosine kinase do:
each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to the kinase domain
what is usually responsible for terminating signal transduction by RTKs
receptor internalization
SH3 domains on proteins recognize what on the protein they bind to:
a specific amino acid sequence
what kind of enzyme activity does the Ras protein display
GTPase
what holds Ras at the inner surface of the plasma membrane
attachment to a lipid group that is embedded in the inner leaflet of the bilayer
how is Ras activity turned off
by hydrolysis of its bound GTP to GDP
