Cytoskeleton Flashcards
Cytoskeletal filaments are ___ and ____
Dynamic and Adaptable
Describe the stability of the cytoskeletal filaments when one protofilament needs to be broken opposed to multiple protofilaments arranged in a sheet.
One protofilament only needs to have one bond broken to remove a piece or break it down the middle, therefore it is thermally unstable
A sheet of protofilaments has multiple bonds all around it that must be broken in order to be disassembled, therefore it is thermally stable
What does staggering do to the strength of the cytoskeletal filaments?
Staggering increases the strength because it allow for more bending and twisting
What are the 3 kinds of Cytoskeletal filaments? Describe the subunits for each kind.
Microfilaments- G or F actin monomers (smallest)
Microtubules- Alpha or Beta Tubulin Dimers
Intermediate Filaments- Lamin
Where are Intermediate Filaments generally found?
What do they bind to?
Anchored to the plasma membrane at the cell-cell junctions
They bind to microtubules, actin filaments, and cell-junctions
Intermediate filaments form mesh-like structures called ____ ____
Nuclear Lamina
Describe the structure of an intermediate filament.
It has a staggered tetramer of two coiled dimers
Monomers -> Dimers -> Tetramers
Staggered means The NH2 and COOH head and tail are arranged slightly apart for the two filaments
What is the disease that is caused by mutations in the nuclear lamina causing nuclear pores to form?
Progeria- increased cellular aging
Microtubules are critical for the ____ in all eukaryotic cells. What 2 structures are they particularly found in?
What do they form during mitosis?
Organization
Major players in cilia and flagella
Form the mitotic spindle used for chromosome segregation
What are the subunits for microtubules?
Where do they arrange themselves during proliferation? What about for catastrophe?
Alpha and Beta Tubulin dimers
Proliferation- Positive end
Catastrophe- Negative end
What is the role of the y-subunit in microtubules?
Begins nucleation (proliferation) of microtubules at the negative end and grows in the positive direction
What is the role of Taxol and what type of cytoskeletal filaments does it affect?
Binds and stabilizes microtubules, therefore preventing any cell growth or disassembly
This is a chemotherapeutic agent because it affects rapidly dividing cells the most
What are the roles of Colchicine and Vinblastine and what type of cytoskeletal filaments does it affect?
Binds to tubulin dimers and prevents their polymerization
What are the 4 main roles of microfilaments? What are its subunits?
Locomotion
Phagocytosis
Cell Division
Contraction
G-actin monomers and F-actin filaments
Describe the structure of Actin filaments.
G-actin/F-actin monomers attach to form a protofilament that has a plus and a minus end
The minus end is Actin bound to ADP, the plus end is Actin bound to ATP (Require ATP to bind to the plus end and allow for polymerization)
What is the role of Phalloidin and what kind of filament does it affect?
Binds and stabilizes Actin filaments, therefore preventing any polymerization or destruction
What is the role of Cytochalasin and what kind of filament does it affect?
Caps the actin filaments plus end, therefore preventing polymerization
What is the role of Latrunculin and what kind of filament does it affect?
Binds to Actin monomers individually before they attach to the actin filament and it prevents their polymerization
What provides strength in tendons, rigidity in teeth and bones, and cushioning in cartilage?
Extracellular Matrix and Basal Lamina, because its composition and properties are controlled and vary by the tissue type and location it is found
What is the main structural protein in the extracellular matrix, connective tissue, and basal lamina?
Collagen
What are 4 locations within the cell that collagen plays major roles in?
Rough ER
Lumen of ER
Golgi Apparatus
Secretory Vesicles
What is the protein that is lossed that causes scurvy?
Collagen
The cofactor Iron Ascorbate, which you get from eating fruits, is lossed, therefore you cannot form Prolyl Hydroxylase, which is required to form collagen within the lumen of the ER
What are the 5 symptoms of Scurvy?
Wounds re-opening Body falls apart Loss of teeth Pale Skin Sunken Eyes
What causes Ehlers- Danlos Syndrome?
A mutation in collagen or the synthesis of collagen genes]
This causes a weakness in the connective tissue of the skin, bones, blood vessels, and organs
What are the 4 types of cellular connections/junctions?
Anchoring Junctions (binds cells together)
Occluding Junctions (link cells together- prevents passage of material)
Channel-Forming Junctions (ions crossing from one cell to another)
Signal-Relaying Junctions (neurons firing onto eachother)
What are the 4 main Cell Adhesion Molecules?
Cadherins (E-Cadherin, E for Epithelium)
Ig-Superfamily (NCAM, N for Neural)
Integrins
Selectins
What are the 2 types of Cadherins?
What is the main function of Cadherins
Classic Cadherins- Calcium dependent, linked to the actin cytoskeleton
Atypical Cadherins- Interact with catenins or Actin Cytoskeleton
Cadherins form junctions between cells
What is Epithelia to Mesenchymal Transition?
EMT is a transition from E-Cadherins to N-Cadherins. In other words, E-Cadherins decrease and N-Cadherins increase.
This occurs in transitional bladder cancer and causes an increase in the invasiveness of the tumor cells and metastatic potential
Describe the function of Ig Superfamily CAMs. Note the different kinds
Calcium INDEPENDENT
Used in immune cell interactions between cells for recognition, binding, and adhesion processes of cells
Different kinds are ICAM and VCAM
What is the function of Selectins?
Note the 3 different types.
Calcium Dependent glycoproteins that bind to extracellular carbohydrates and play an important role in the Leukocyte Adhesion cascade by allowing for the rolling process to occur
Types are:
Endothelial (E-Selectin)
Leukocyte (L-Selectin)
Platelet (P-Selectin)
What are the 3 functions of Integrins?
These couple the Extracellular Matrix to the Cytoskeleton
Ex. Fibronectin, Collagen, Laminin, Vitronectin
Activate Signaling pathways by interacting with Tyrosine Kinase Receptors
Allow for the adhesion of leukocytes and transmigration to affected sites
