Term
| What is the function of intermediate filaments? |
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Definition
| Structural support of the cell and allow cells to withstand mechanical stress |
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Term
| What are intermediate filaments called in the nucleus? |
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Definition
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Term
| What kind of junction is associated with intermediate filaments? What does it do? |
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Definition
| Desmosome. This helps hold cells together. Cadherins are involved in this structure. |
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Term
| What is the general structure of intermediate filaments? How many monomers per filament? |
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Definition
| About 24 monomers per filament is coiled in kinda a ropelike way. |
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Term
| What is the function of microtubules? |
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Definition
| Intracellular transport, organization of cellular interior, ciliary movement, MITOSIS |
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Term
| What are the motors associated with microtubules? In which direction does each go? |
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Definition
| Dynein and kinesin. Dynein goes towards the -. Kinesin goes towards the +. |
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Term
| What do dynein and kinesin use for energy? |
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Definition
| They use hydrolysis of ATP. |
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Term
| What's the structure of dynein and kinesin? |
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Definition
| Dynein and kinesin both have 2 globular heads that bind the microtubule. They also have a tail region that binds the cargo. Kinesin has two heavy chains and two light chains. Dynein has two heavy chains and many light proteins. |
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Term
| In relation to where dynein and kinesin go, where is the axonal terminal? What is the axonal terminal? Which motor will bring vesicles to the axonal terminal? |
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Definition
| Axonal terminal is essentially where the synapse is. This is the + end of the neuron. So, kinesin is gonna bring stuff there. |
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Term
| What's the structure of a microtubule? |
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Definition
| First off, it is a tube. It has a lumen. It is made of both alpha and beta subunits which stack on top of each other to make protofilaments. Then the long protofilaments (13 of them) join to make the tubule with a lumen. |
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Term
| Which end is the beta tubulin and which end is the alpha tubulin? |
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Definition
| Its the opposite of what you'd think. The beta is oriented towards the plus end and the alpha is minus. It doesn't pay to be an alpha. |
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Term
| Do intermediate filaments have motors? |
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Definition
| No, they aren't involved in transporting stuff. |
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Term
| How do microtubules grow and shrink? |
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Definition
| Well, GTP-associated tubulin gets added to the + end (growth), and GDP-associated tubulin falls off (shrinkage) |
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Term
| What motor is associated with retrieval of cargo from an axonal terminal? |
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Definition
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Term
| What do the tails of dynein and kinesin generally associate with? |
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Definition
| They associate with a vesicle they are transporting. Specifically they bind to adaptin, intermembrane proteins, or cargo receptors in the vesicular membrane. |
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Term
| What does ATP hydrolysis do specifically that makes dynein and kinesin move? |
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Definition
| GTP hydrolysis causes a conformational change which gives the energy for movement. |
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Term
| Where is the end point of microtubules? (at the - end I mean) |
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Definition
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Term
| What does treadmilling refer to in reference to microtubules? |
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Definition
| tubulin is being added to the + end as it is coming off of the - end. Thus, the strand stays the same length. |
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Term
| How might treadmilling create energy? |
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Definition
| It has been proposed that the last alpha subunit of tubulin can serve as a GAP (GTPase activating proteins), and thus hydrolyze the GTP to GDP on the adhering beta subunit, which causes the tubulin to disassociate from the protofilament. Hydrolysis of GTP creates energy. |
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Term
| What is another word for centrosome? |
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Definition
| Microtubule organizing center (MTOC) |
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Term
| What's the process of microtubules and cell division? |
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Definition
| Well... basically you have a centriole which is surrounded by the centromere (where all the - ends of the microtubules attach). Then the centriole splits into two, so you have microtubules for each daughter cell. (This happens prior to mitosis). Then, you get a mitotic spindle which forms and attaches to chromosomes lined up in the metaphase plate. The + end of the microtubules is here. KINETOCHORES associate the microtubule with the chromosome. In anaphase, proteins associated with dynein help to shrink those microtubules associated with dynein. SO, the stuff attached to the chromosomes via kinetochore is traveling towards the nucleus (that's usually where the centromere is). Then, you get appropriate numbers of chromosomes in each cell. |
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Term
| What kinda drugs affect microtubules and why? |
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Definition
| Taxol, colchicine, vinblastin, vinchristine are drugs that affect microtubles and stop cells from dividing/kill dividing cells by arresting mitotic spindle. Cancerous cells are rapidly dividing, so this is important! |
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Term
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Definition
| It is involved in cell movement and muscle movement. |
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Term
| What motors are associated with actin? |
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Definition
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Term
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Definition
| it is involved with vesicle transport. |
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Term
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Definition
| it does muscle and cell movement. |
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Term
| What is actin's structure? |
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Definition
| It is a helix of two strands of polymerated actin molecules. |
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Term
| Which direction are actin molecules added and taken off? How is this different from microtubules? |
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Definition
| They are added as ATP-bound to the plus end, and come off as ADP-bound on the minus end. This is different from microtubules because they use GTP bound tubulin proteins. |
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Term
| What is the structure of myosin I? |
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Definition
| It has a head and a tail. The head interacts with actin and the tail with the vesicular cargo. |
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Term
| What is the structure of myosin II? |
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Definition
| It has a head and a long tail. It usually comes together in a long strand (called a myosin filament or thick filament) |
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Term
| Where is ATPase on the myosin II molecule? |
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Definition
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Term
| When actin proteins are bound in a polymer, what are they referred to as? |
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Definition
| f-actin. g-actin is unbound. |
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Term
| Tell me the story of muscle contraction. |
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Definition
| Well, you get an action potential which activates Ca2+ channels in the plasma membrane. These then activate Ca2+ channels in the sarcoplasmic reticulum. Then the Ca++ binds troponin, which causes a conformational change knocking tropomyosin out of the way. This allows actin and myosin to touch and then the actin contracts over the myosin. The ca++ gets absorbed and the contraction stops. The myosin does not move. |
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Term
| Why would calcium want to get into the cytoplasm for muscle contraction? |
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Definition
| The actin/myosin are localized near the plasma membrane. |
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