Tuulin Subunit
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All Answers should be written in the provided space. Each Question is worth 5 pts.
A maximum of 20 pts may be added to your first exam 20 x (correct pts / total pts)
Question 1 Actin and tubulin form self-assembling polymers. Where on the filaments do subunits exchange with free monomers?
Subunit exchange with free monomers occurs at the end of filaments. In actin filaments, subunits can be freely exchanged at both ends of the filament (pointed and barbed ends) until the actin formation reaches a steady state. At this point, the subunits are added to the barbed end and lost from the pointed end simultaneously in a phenomenon known as treadmilling. In microtubules, tubulin subunits are added …show more content…
Actin filaments are joined together to form higher order structures. These structures include contractile and parallel bundles that are composed of antiparallel or parallel actin filaments, respectively. Actin filaments within these structures are cross-linked by accessory proteins known as actin binding proteins. These proteins connect two actin filaments through its two actin-binding sites or dimerization with actin domains. Crosslinking actin filaments can be performed by fimbrin proteins that attach filaments in a parallel fashion to facilitate movement. Thus, they are localized in microvilli, filopodia, and focal adhesions. Other proteins including α actinin and spectrin connect actin filaments in an antiparallel way to allow contractions. α actinin proteins are located in stress fibers, filopodia, and muscle Z lines, whereas spectrin proteins are found at the cell …show more content…
The doublet microtubules are connected to the central microtubules by radial spokes that will maintain the same side of doublet microtubules as they move. Also, the fused pairs of doublet microtubules are interconnected by nexin to coordinate the movement of microtubules and prevent the disruption of the axonemal structure by dynein proteins. However, dynein proteins are the major motor protein required for ciliary movement and they move toward the negative end of the contiguous B tubule. Dynein proteins will bind to the activated dynein arms of microtubules that will be on one side of the axoneme resulting in a bent cilium.
Question 9 Plectin is a protein associated with the cytoskeleton that was discussed in class. Describe the function of plectin. Would a targeted disruption of plectin be embryonic lethal? Why?
Plectin is a linker protein that maintains the overall structural integrity of cells by crosslinking different cytoskeletal elements. Plectin is essential because its loss results in degeneration of keratinocytes and skin detachment, myopathies in skeletal muscle and disintegration of cardiomyocytes (Andrä., et al (1997) Genes & development, 11(23), 3143-3156).
Question 10 Identify 2 mechanisms used to move major membrane lipids throughout the
All Answers should be written in the provided space. Each Question is worth 5 pts.
A maximum of 20 pts may be added to your first exam 20 x (correct pts / total pts)
Question 1 Actin and tubulin form self-assembling polymers. Where on the filaments do subunits exchange with free monomers?
Subunit exchange with free monomers occurs at the end of filaments. In actin filaments, subunits can be freely exchanged at both ends of the filament (pointed and barbed ends) until the actin formation reaches a steady state. At this point, the subunits are added to the barbed end and lost from the pointed end simultaneously in a phenomenon known as treadmilling. In microtubules, tubulin subunits are added …show more content…
Actin filaments are joined together to form higher order structures. These structures include contractile and parallel bundles that are composed of antiparallel or parallel actin filaments, respectively. Actin filaments within these structures are cross-linked by accessory proteins known as actin binding proteins. These proteins connect two actin filaments through its two actin-binding sites or dimerization with actin domains. Crosslinking actin filaments can be performed by fimbrin proteins that attach filaments in a parallel fashion to facilitate movement. Thus, they are localized in microvilli, filopodia, and focal adhesions. Other proteins including α actinin and spectrin connect actin filaments in an antiparallel way to allow contractions. α actinin proteins are located in stress fibers, filopodia, and muscle Z lines, whereas spectrin proteins are found at the cell …show more content…
The doublet microtubules are connected to the central microtubules by radial spokes that will maintain the same side of doublet microtubules as they move. Also, the fused pairs of doublet microtubules are interconnected by nexin to coordinate the movement of microtubules and prevent the disruption of the axonemal structure by dynein proteins. However, dynein proteins are the major motor protein required for ciliary movement and they move toward the negative end of the contiguous B tubule. Dynein proteins will bind to the activated dynein arms of microtubules that will be on one side of the axoneme resulting in a bent cilium.
Question 9 Plectin is a protein associated with the cytoskeleton that was discussed in class. Describe the function of plectin. Would a targeted disruption of plectin be embryonic lethal? Why?
Plectin is a linker protein that maintains the overall structural integrity of cells by crosslinking different cytoskeletal elements. Plectin is essential because its loss results in degeneration of keratinocytes and skin detachment, myopathies in skeletal muscle and disintegration of cardiomyocytes (Andrä., et al (1997) Genes & development, 11(23), 3143-3156).
Question 10 Identify 2 mechanisms used to move major membrane lipids throughout the