not too details, just main points please... 1. What you should know about microt
ID: 257876 • Letter: N
Question
not too details, just main points please...
1. What you should know about microtubles
- MT structure, what they are made of
- MT function
- Motor proteins(kinesins&dyneins)
- How kinesins move, coupling to ATP hydrolysis
- Microtubule Organizing Center (MTOC), how MTs are nucleated
- MT dynamics, how it's affected by drugs and MAPs
- dynamic instability and how its linked to GTP/GDP cycle
- cilia/flagella, axoneme structure
- how cilia/flagella move and the role of dynein
-intra-flagellar transport
2. What you should know about actin filaments
- F-actin structure
- F-actin Function
- Motor proteins (myosins)
- Actin dynamics, how it's affected by actin-binding proteins
- the concept of critical concentration
- actin/myosin structure and function in the contezt of muscle
- how muscle contract
- actinomyosin cycle (myosin movement), coupling to ATP hydrolysis
- How cells move and change shape, using actin
3. What you should know about IF
- IF strcuture, what they are made of
- IF function, roles inside and outside cells
- Regulation of nuclear IF in the cell cycle
- be able to compare major features of IF, Actin, and MTs
Bacterial cytoskeleton, that bacteria have proteins that
- polymerize
-affect cell shape, cytokinesis, ect.
- play analogous roles to MT, F-actin
4. what you should know about the cell cycle
- parts of the cell cycle, stages of mitosis
- MPF; how it was identified, what it is made of (cyclin and cdk)
- Universality of cyclin/Cdks (in yeast, frogs, etc.)
-how Cdk activity is regulated (many mechanisms)
- how Cdks function (by phosphorylation)
- how multiple cdks divide their function
- how the spindle is formed and mistakes corrected
- the role of motors and MY dynamics in above
- the tolr of proteolysis in mitotic transitions
- what a checkpoint is
- how checkpoints provide an additional layer of cell cycle regulation in case of damage
Explanation / Answer
1. Microtubules are long, hollow, unbranched cylinders about 25 nm in diameter. They have mainly two roles: forming a rigid internal skeleton for some cells and acting as a framework along which motor proteins can move structures in the cell.
Micrtubules are assembled from molecules of protein tubulin. Tubulin is a dimer, made up of two monomers known as alpha tubulin and beta tubulin. Microtubuleses radiate from a region of the cell called Microtubule organizing center. Tubule polymerisation contributes to the rigidity. They are associated with movable cell appendages namely flagella and cilia.
Flagella are usually found singly or in pairs. Waves of bending propagate from one end of a flagellum to the other in snake like undulation. Prokaryotic flagella lack microtubules and dynein.
The nine microtubule doublets of cilia and flagella are linked by proteins. The motion of cilia and flagella results from the sliding of the microtubules past each other. This sliding is driven by a motor protein called dynein by changing its shape.
All motor proteins undergo reversible shape changes powered by energy from ATP. Dynein molecules attached to one microtubule doublet bind to a neighbouring doublet. As the dynein molecules change shape.they move the microtubule past its neighbour.
Cilia beat stiffly in one direction and recover flexibly in other direction, so that the rcovery stroke does not undo the work of the power stroke.
A typical cila or flagella contains a 9+2 array of microubules. It has nine fused pairs of microtubules called doublets, forming outer cylinder and one pair of unfused microtubule at the center. A spoke radiates from one microtubule of each doublet to the centre of the structure.
Dynein and another motor protein kinesin are responsible for carrying protein laded vesicles from one part of the cell to another. Dynein moves attached organelles towards the minus end, while kinesin moves them towards the plus end.
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