Flashcards in Muscle contraction Deck (55):
Where does actins contractile properties come from?
interaction with its motor protein myosin
What is cell contraction involved in?
Cell crawling - pulling the tail end of the cell forward
When does the contractile filaments form form the cleavage furrow?
What does myosin move along for movement?
What provides the energy for myosin movement along actin filaments?
myosin hydrolyze ATP
What does Myosin function like?
dynein and kinesin that move along MTs
In which direction does all of myosin move?
toward the plus end (like kinesin)
How many different myosins are there?
14 different kinds of myosin
What does all myosin share?
homology in their amino acid sequence
they differ mostly in their C -terminus tail
some in their N terminus tail
Which eukaryotic cells are myosin most common to?
all/most eukaryotic cells (protozoa, plants, animals) some are taxon specific
What does myosin function as?
three as a monomer
What are the the myosin families that function as a monomer?
What are the domains of the Myosin I family?
one head ATPase domain
one tail cargo binding domain
What is the function of the head domain on the myosin I family?
interacts w/ actin filaments (factin binding domain)
hydrolyze ATP - allows it to walk along the actin filament
What is the function of the tail domain in myosin I family?
interacts with components
is specific to cargo
What is various myosin I proteins?
C - terminus that bind different cargo
Where are myosin II proteins most abundant in?
can be found in non muscle cells
What do Myosin II dimers cluster to form at their tail domain in skeletal muscle?
thick myosin filament
common in muscle cells
What does the myosin monomers and dimers show?
Why are myosin monomer and dimers bipolar?
one set of heads binds actin filaments pilling them in one direction
another set of heads binds to another set of actin filaments and pulls the opposite direction
What is the overall effect on actin of opposite binding heads of myosin?
slide sets of oppositely oriented actin filaments past one another - generation of overall contractile force
What are skeletal muscle formed from?
parallel arrangements of multiple muscle fibers
What is a single skeletal muscle cell equal to?
how does a muscle fiber run?
whole length of a muscle
How long are muscle fibers?
50 m in diameter
How are muscle fibers formed?
from fusion of many precursor cells
Why are muscle fibers multi nucleated?
because the precursor cells retain their nucleus
What is a sacrolemma?
plasma membrane of a muscle fiber
What are T- tubules?
in sacrolemma they are deep invaginations into the center of the fiber
What are myofibrils?
contractile elements of muscle fiber
What is each muscle fiber compose of?
multiple myofibrils that run along the long axis of the muscle
How long are myofibrils?
sometimes long as the muscle fiber itself
1-2m in diameter
What are sacromeres?
individual unit that make up myofibrils
How long are sacromeres?
2.5-3 m long
how many sacromeres in series is in a muscle 30 cm long?
10,000 sacromeres in series
3 * 10000 = 30000 = 30 cm
What gives the cardiac and skeletal muscle its striated appearance?
the repeating structure of sacromeres
What are sacromeres compose of?
What is the thin fibers in sacromeres?
What does the plus end of actin filaments interact with?
where does each minus end of actin filaments orient?
toward the center of the sacromere, overlaps with myosin filaments
What are the thick filaments in sacromeres?
bipolar clusters of Myosin II
What is the position of thick filaments (myosin II) in sacromeres?
centrally positioned in each sacromere
What is the M- line
mid point of thick filament where myosin head begin being arranged in the opposite direction
What is the Z-disc?
point of attachment of actin filaments
What is the Z- disc built of?
How does the plus end of actin filaments attach to Z-line?
actin binding protein CapZ
prevents depolymerization of plus end and holds them in a regularly spaced arrangement
What is nebulin?
actin side binding protein that determines length of actin filaments
What is the minus end of capped of with?
What is titian?
side binding protein for myosin (determines length of thick filament)
act as a molecular spring to help bring sacromers back to its appropriate length after to much stretch
Where does titin stretches from?
the Z disc into thick filament, where it interacts with the myosin tails and up to the M-line
(there are two titin ends from Z disc to Z disc)
how are sacromeres viewed using polarized light microscopy?
display a characteristic pattern of light and dark regions
What is the I-band?
What does the I-band span?
technically spans two sacromeres but w/in sacromeres runs Z-line to outer edge of thick myosin filaments
thin act filaments only (no overlap with myosin)
What is the A band?
darker staining region in the middle of the sacromere
may overlap with actin filaments towards either end