BIO 2 EXAM 1 Cytoskeleton and Tissue Types Flashcards
What gives eukaryotic cells their shapes…
Cytoskeleton = cellular skeleton
Types of Cytoskeletons…
Microtubules (MTs)
Microfilaments (MFs)
Intermediate Filaments (IFs)
Defining Microtubules…
Microtubules are the thickest element of the cytoskeleton
Hollow tubes
The polymer of alpha/beta Tubulin heterodimers
Important for cell division
cilia/flagellavesicle movement
13 protofilaments
Each interior tubulin has four contactsabone protofilament
Ends are different + end – end
Where are the ends of the microtubule anchored…
the end is anchored at an MTOC (Microtubule Organizing Center)
In most cells, the MTOC is the centrosome located near the nucleus
Additional information:
Centrioles in the interior
rings of 13 g-tubulin proteins
Additional and removal of Microtubules…
a/b tubulin can only be added or removed from the + end, not from the – end (anchored), not from the middle
Functions within Microtubules…
a/b tubulin binds to a molecule of GTP or GDP.
Subtle change in protein shapea/b tubulin with GTP
promotes polymerization at + enda/b tubulin with GDP
promotes depolymerization from + end only
a/b tubulin cuts GTP → GDP slowly
After a while, GTP→GDP
Growing microtubules have a…
GTP Cap
When growth stops, GTP→GDP catches up. MT depolymerizes
Defining Microfilaments…
Microfilaments are the thinnest part of the cytoskeleton
The polymer of actin, one of the most abundant proteins
important for cell shape
cell movement
muscle contraction cell division
Actin polymerizes as a helix
Ends are different: + and – (or ‘barbed’ and ‘pointed’)
Additional and removal of microfilaments…
Can add or remove actin monomers from any end (but not the middle)
Actin-ATP promotes polymerization; Actin-ADP promotes depolymerization
Defining Intermediate Filaments…
Made of many different proteins, not tubulin, not actin, Keratin as an example
intermediate in diameter
important for cell strength
Less turnover than MTs or MFs
Humans have 54 different Keratin proteins, about half are Type I and half are Type II
Ends are not different
Each end has C-termini recessed
Physical traits of an intermediate filament…
Long central region that is an extended a helix
Blob-like N- and C-terminal domains to monomers bind each other
Two monomers bind each otherCoiled coil domain
Two dimers bind each other to make a tetramer
Tetramers polymerize head-to-tail
Eight across
Twisted together for strength
Why are IF’s different…
different from MTs and MFs as, No nucleotide binding, Ends are the same, Less dynamic instability.
The four different tissue types…
Muscle
Nervous
Connective tissue includes adipose (fat), blood, bone, cartilage, etc.
Epithelial tissues cover surfaces, internal external (basal and apical side (top))
