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34 Cards in this Set

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  • Back
What is the structure of an Axoneme
a cylinder of microtubules, 9 doublet microtubules (A - complete microtubule with 13 protofilaments and B an incomplete microtubule with 9 protofilaments that shares 3 from A), all around a central pair of 2 microtubules
What is a Basal Body and what does it do?
a microtubule organizing center that nucleates the - end of the axoneme
What is axonemal dynein?
it's covalently attached to the A microtubule and walks along the neighboring microtubule towards the - end
What causes the specific movements in cilia and flagella?
patterned activation/inhibition of dynein
what is Nexin?
Like a spring between adjacent doublet microtubules that holds them together, but still allows movement
what is a Radial Spoke?
holds outside doublet microtubules in register to the central doublet
Name 4 differences between cilia and flagella
number per cell, length, pattern of beating, direction of movement
cilia vs flagella: number per cell
many cilia per cell (if it has cilia). Usually 1, sometimes 2 flagella per cell
cilia vs flagella: length
cilia are short (1-2 micro m). flagella are long (100 micro m)
cilia vs flagella: pattern of beating
cilia - like an oar or backstroke
flagella - undulating, corkscrew pattern
cilia vs flagella: direction of movement
cilia - perpendicular to direction of movement
flagella - parallel to direction of movement
What are myosins in general?
molecular motor proteins that walk along the actin cytoskeleton
What is myosin II specifically?
walks towards the + end of an actin filament
What is the structure of muscle? (general)
muscles are bundles of muscle fibers. muscle fibers (or cells), are bundles of myofibrils. Myofibrils are made up of many sarcomeres.
Describe a sarcomere (general)
Defined as from Z line to Z line. Actin filaments perpendicular and stabilized at + end on Z line. Heavy chains (myosin II) in between actin filaments.
What is the Z line?
stabilizes and locks the + ends of actin filaments. defines boundaries of sarcomeres
What is the A band?
the length of heavy chain (myosin II)
What is the I band?
the region around the Z line that is devoid of heavy chain
What is the H zone?
the region of heavy chain only
A cross section of a muscle would show what?
A heavy chain surrounded by 6 light chains
What is an oligomer?
A protein that exists as multiple subunits associated
How does myosin II exist?
as an oligomer. the heads have an orientation
What is the structure of myosin II protein?
A head that binds to actin and hydrolyzes ATP. A neck like a spring. Tails that mediate oligomerization.
What are the four steps of muscle contraction?
1. Myosin w/ADP associates with actin
2. When myosin binds w/actin, it does a "power stroke" and releases ADP
3. ATP binds the myosin and it is released from actin
4. The ATP on the myosin is hydrolyzed "cocking the spring" of myosin
Muscle contraction is an example of converting _____ energy into ______ energy
chemical, potential
What is the structure of troponin?
3 domains:
i - inhibitory domain
c - binds to Ca2+
t - binds to tropomyosin
What is the structure of tropomyosin?
long protein draped along actin filament, blocking actin/myosin interactions
How do troponin and tropomyosin interact to regulate muscle contraction?
In the presence of elevated Ca2+, troponin binds Ca2+, which changes the conformation of tropomyosin, removing it from the inhibitory site. This allows myosin to bind to actin -> muscle contraction!
nerve to muscle: 1. action potential
depolarization down the axon. Na+ in, K+ out
nerve to muscle: 2. presynaptic terminus
voltage gated channels open, calcium floods in, vesicles at presynaptic terminus fuse to membrane and release acetylcholine
nerve to muscle: 3. synaptic cleft
acetylcholine binds acetylcholine receptors on the muscle, which are part of ligand gated ion channels (the ligand being acetylcholine). the channels open and let in lots of Na+
nerve to muscle: 4. muscle cell
when Na+ floods the cell, voltage gated Ca2+ channels open, and Ca2+ floods the cell, binds troponin, changes conformation, moves tropomyosin, allows myosin to bind actin, muscles contract w/help of ATP
How do acetylcholine vesicles get to presynaptic terminus?
transported from neuron cell body down the axon by kinesin on microtubules
How do you build muscle?
add more myosin monomers to myosin thick filament. Can only add more myosin by adding more sarcomeres.