Cytoskeleton Flashcards
What is the interior of the cell composed of?
Cytoskeleton, Cytosol. and organelles
What are the filler structures of the cell?
Cytoskeleton and Cytososl
Do not contain essential biological molecules
function is structural
Cytoskeleton
Protein filaments and is found throughout the inside of the cell
Cytosol
provides 50% of the cell volume; site of protein synthesis
How many types of actin are there and what is the size of 1 filaments?
6 types and 6nm
How many types of Microtubules are there and what is the size of 1 filament?
12 type and 23 nm
How many types of Intermediate filaments are there and what is the size of one filament?
31 types and 10nm
Which filaments are like cables?
microfilaments and intermediate filaments
Which filaments acts like a cellular support beam?
Microtubules
What is the most abund. cytoskeletal element in eukaryotes?
Actin
what is the main component of Microfilaments?
Actin
It is double stranded because the molecules work together
Form a double helix
Where is actin found?
Near the cell membrane
Describe actin
It is a linear polymer of actin subunits
generates force by elongation and shortening of opposing ends
Actin is a tract for movement of which motor protein?
Myosin
What controls Actin?
The Rho family of small GTP binding proteins that are ATP dependent
What are the components of Rho family?
Rho - contractile acto-myosin filament
Rac- lamellipodia
CdC42 - filopodia
Microvilli are made of?
F-Actin
Which two elements stabilize anchoring and cross linking of F-actin?
Villin and Fimbrin
Which two elements anchor the F-actin to the cell membrane?
Myosin I and Calmodulin
What type of subunits make up microtubules?
tubulin -> alpha and beta -> bind together to form a protofilament
13 protofilaments make up a microtubule
bind GTP for polymerization
which cytoskeletal element resist compression?
Microtubules
Describe microtubules
long, hollow. and cylindrical Work separately to provide tracks on which organelles can travel from center of the cell outward More rigid than actin unstable/continuous growth and decay Minus end - nucleus Plus end - cell membrane
Microtubules organize around?
Centrosome - which is at the center near the nucleus
one end of the microtubule is embedded in the centrosome and the microtubule grows out from there
What are the key roles of microtubules?
Intracellular transport (w/ dyneins and kinesins) of orgganelles such as mitochondria and vesicle s
The axoneme
the mitotic spindle
synthesis of cell wall in plants
What are the molecules that bind microtubules?
Colchicine
Tau (abnormal in Alzheimer’s)
Dynein (moves toward minus end, center)
Kinesin (moves towards plus end, cell membrane)
What is the function of colchicine?
depresses MT assembly
Use to treat Gout - inhibits mitosis in neutrophils by inhibiting the mitotic spindle
During cell division chromosomes attach to which part of the chromosome?
Kinetichore
What are the two type of microtubule structurres?
9 triplet (star shaped) and the 9 doublet + 2 ( wheel shaped)
What is an example of the nine triplet?
Centrioles and basal body
What is an example of the 9 doublet +2?
Cilia and Flagella
What is another name for the 9+2 arrangement?
axoneme
Which protein connects the subunits (tubulin) together?
Dynein
Which protein connects the doublets to one another?
Nexin
Abnormal Ciliary Dynein causes?
Kartagener’s Syndrome
What are the characteristics of Kartagener’s Syndrome?
Motor deficit
Respiratory System Abnormalities -> Situs Inversus
What is situs Inversus?
When organs are switched to the opposite side of the body (thoracic and abdominal)
Ciliary movement aids in organogenesis in the early embryo
What is the cause of Bardet-Biedi Syndrome?
Disruption of the sensory function of cilia "genetic disorder" CNS malfunction (retinopathy, learning disability)
Characteristics of Sensory Cilia
Primary - Nuerons, Chondrocytes, Kidney Epithelium
Receptors for neurotransmitters and many other molecules are localized where?
To cilia
How many cilium do CNS neurons commonly have?
One
What are characteristics of intermediate filaments?
rope like and fibrous
two anti-parallel helices/dimers forming tetramers
Extend through cytosol (like a 3-D structure)
more stabel
heterogenous constituent
anchors organelles
Which cytoskeletal element help resist stress and increase cellular stability?
Intermediate filaments
Which cytoskeleton element helps maintain cell shape by bearing tension?
Intermediate filaments
What is the structural element of nuclear lamina and sarcomeres?
Intermediate Filaments
What are examples of intermediate elements?
Vimentin (mesenchymal-connective tissue)
Glial Fibrilary acid protein ( glial cells-astrocytes)
Neurofilament proteins (neuronal processes)
Desmin (muscle)
Keratin (epithelium)
Nuclear lamins (interconnect nuclear pores)
Which intermediate element is inserted into desmosomes and involved in cell to cell adhesions and cell to matrix adhesions.
Keratin
What is Myosin?
A motor protein that is ATP dependent
actin-based motility
What are the actions of Myosin?
Actin binding
ATP hydrolysis
Force transduction
T/F All Prokaryotic cells contain myosin isoforms
False. It is eukaryotes
some isoforms have specialized functions in certain cell types while other isoforms are ubiquitous
What are the three molecular domains of Myosin?
Head, Neck, and body
What is the function of the Myosin Head?
bind actin
use ATP hydrolysis to generate force and walk along filament toward the positive end
What is the function of the Myosin neck?
it is the linker
lever arm for transducing the force generated by the catalytic motor domain
contains the binding site for myosin light chains (distinct protein that form part of macromolecular complex and have regulatory functions)
What is the function of the Myosin tail?
mediates interaction w/ cargo molecules and/or other myosin subunits
Sometimes regulates motor activity
Which form of Myosin moves towards the negative instead of the positive end?
Mysoin VI (6)
Myosin I is involved in?
Vesicular transport (monomer- 1 tail)
Myosin II is involved in?
Muscle contraction (dimer - 2 tails wrapped and bound to Cap2 by Titin)
In the sarcomere where is the head and tail located?
Tail - M line
Head - I band
What does cell movement involve?
Myosin + actin
Focal contact made of integrin proteins
Movement of actin and loosening of focal contact permits cell movement
