Lec 18 Flashcards
Cytoskeleton
Enormous protein filaments made of chains of globular proteins and bundles of fibrous proteins
Microtubules is made up of
Subunit protein- Tubulin
Protein filament- Microtubules
Tubulin is made up of
Polypeptides
Tubulin connects to make a
Protofilament
Protofilaments combines to form
Microtubules
Polypeptides are made by
Different genes on different chromosomes
Protofilaments can be arranged in bundles known as
Singlets
Doublets
Triplets
Microtubule polarity
There is a + and - end that is not due to charge
+ means active
Assembly and disassembly of microtubules
Tubulins are added and removed from the plus end
Microtubules are connected to
Centrosomes
Centrosomes are a
Ball of proteins
How is the negative end of the microtubule connected to the centrosome
With a Gamma Tubulin Ring Complex
Microtubules outside the cell
Remain active outside the cell
Microtubules grow and shrink
Independently of their neighbors
Tubulin is regulated by
GTP
Both tubulin polypeptides on microtubules contain
Nucleotides
One is accessible by GTP or GDP
The other is inaccessible and is always GTP
D form
Microtubules
GDP and GTP
Inactive form that forms curved protofilaments
T form
Microtubules
GTP and GTP
Active form that forms straight protofilaments
How to change from D to T form
Nucleotide replacement that occurs when in the cytosol
Hydrolysis occurs when part of a microtubule
T form microfilament addition
Protofilaments are added in the GTP active form
Even when the GTP is inactive, the protofilaments that are added are still straight
D form microfilament removal
Protofilaments that are curved and in the inactive form fall off
Once they’re in the cytosol, nucleotide replacement happens which puts the protofilaments back into the T form
Dynamic instability
Cells being unstable
It is desirable as it supports the cell
Dynamic instability
Compression
Trying to crush the cell
Dynamic instability
Tension
Trying to rip the cell
Microtubules help cells resist
Compression
Microtubules during prophase
Extend and contract to find the centromeres
Once the microtubule contacts the centromere during prophase, it is stabilized by
Kinetochore proteins
RBCs and microtubules
Disc shape due to ring of microtubules
Neuron axons and microtubules
Axons are too long to have their microtubules connected to the centrosome
They are instead stabilized by proteins called tau
