Cell Structure 3 Flashcards
What structures are associated with desmosomes and help anchor the nucleus?
Intermediate filaments.
T or F. Many integral membrane proteins are anchored by the actin cortex.
True.
Microfilaments are composed of ______.
Actin.
What supports the cell membrane and anchors integral proteins?
Actin cortex.
Cytoplasmic streaming, cell motility, muscle contraction, and cell division all have what in common?
Microfilament involvement.
The movement of actin filaments by addition and loss of actin on the + and - end is a process called _________.
Treadmilling.
Which actin binding proteins are involved in bundling?
Fascin, fibrin. Important for microvilli.
Which actin binding proteins are involved in cross-linking?
Spectrin, filamin, adductin, protein 4.1, protein 4.9. Important for actin cortex. A specter filled a duct with 4 proteins.
Which actin binding protein are involved with filament severing?
Gelsonin
Which actin binding proteins are involved in capping? What does capping do to actin filaments?
Tropomodulin. Stops growth at + end.
Which actin binding proteins are involved in motor?
Myosins I- IX.
T or F. Intermediate filaments are structurally and biochemically homologous.
False. Intermediate filaments are structurally homologous but biochemically different.
Name 3 functions of intermediate filaments.
- Maintenance of cell shape
- Anchorage of nucleus and other organelles.
- Formation of nuclear lamina.
How thick is an actin filament? Intermediate filament? Microtubule?
- Actin: 2nm.
- Intermediate filament: 8-12 nm.
- 25 nm.
______ ________ ________ allow epidermal cells to resist stress. (3 words)
Cytokeratin intermediate filaments.
Class I Intermediate filaments: Name 1 component polypeptide and the corresponding location where the filament is found.
Component polypeptide: acidic and basic cytokeratins.
Location: All epithelial cells.
Class II Intermediate filaments: Name 3 component polypeptides and the corresponding locations where the filament are found.
- Polypeptide: Vimentin, Location: Cells of mesenchymal origin (endothelium, myofibroblasts, smooth muscle)
- Polypeptide: Desmin, Location: Muscle.
- Glial fibrillary acidic protein, Location: Glial cells (Astrocytes, Schwann cells)
Class III Intermediate filaments: Name 1 component polypeptide and the corresponding location where the filament is found.
Polypeptide: Neurofilament proteins, Location: Neurons.
Class IV Intermediate filaments: Name 1 component polypeptide and the corresponding location where the filament is found.
Polypeptide: Nuclear lamins A, B, C. Location: Nuclear lamina of all cells.
Microtubules are composed of _____ and ______ tubulin dimers.
Alpha, Beta
T or F. Like actin, microtubules grow only at the + end and shortens only at the - end.
False. Microtubules can also shorten at the + end.
The - end of a microtubule is embedded in the ____________.
Microtubule organizing center (MTOC)
T or F. Kinesin and dynein are ATPases.
True.
Kinesin is an ______ motor.
Anterograde, it moves from - to +.
Dynein is a _______ motor.
Retrograde, moves from + to -.
What are the 3 different surfaces of an epithelial cell?
Apical, lateral, basal.
Microvilli are composed of which filament?
Actin.
What is a consequence of Microvillus Inclusion Disease?
Inability to absorb nutrients, refractory diarrhea.
Cilia in the human trachea help _____________.
Moves fluid/material over the epithelium.
What is a basal body?
A nucleating center for microtubules.
How is a ciliary axoneme organized?
9 + 2 organization.
Ciliary axonemes move by _______ (dynein or kinesin) dependent hydrolysis of ATP.
Dynein.
A ciliary axoneme suffering from Kartegener’s Syndrome lacks ______.
Dynein arms.
T or F. Like most cilia, stereocilia is made of microtubules. Where are stereocilia located?
False. They are actually long microvilli and are made up of actin. Located on epididymis and hair cells of cochlea.
How does kinocilia differ from typical cilia? Where can you find kinocilia?
Kinocilia is nonmotile and organized 9 + 0. It is present on hair cells of inner ear.
The _______ (apical, lateral, basal) wall is heavily involved in adhesion.
Lateral.
What are functions of Tight Junctions?
- Prevents passage of water soluble molecules
- Prevents movement of integral membrane proteins.
- Connects cells to neighbors
- Maintains gradients.
Tight junctions consists of a complex of proteins which include _____ and _____.
Occludin, claudin.
Name 2 types of anchoring junctions (anchor between cells).
Adherens junctions. Desmosomes.
What are the components of the adherens junction?
Ca2+ dependent adhesive interactions mediated by cadherin proteins. Actin filaments anchored via catenin and vinculin.
What are the components of desmosomes?
Adhesive action mediated by desmoglein and desmoplakin. Intermediate filaments anchored to desmoplakin/pakoglobin attachment plaque.
Gap junctions are channels composed of ______.
Connexons (connexons are made of 6 connexin subunits).
What are 2 functions of gap junctions?
- Allows passage of ions and small molecules between cells.
- Couples cells electrically and metabolically.
What are 3 functions of basement membranes and Cell-to-Extracellular Matrix connection?
- Support
- Adhesion
- Filtration
What are 4 major components of basement membrane/cell-to-extracellular matrix connections?
- Laminin
- Type IV collagen
- Entactin
- Perlecan
What are integrins? What do they do?
Transmembrane proteins consisting of a/b heterodimer. Important in signal transduction via coupling to second messenger systems.
Alpha chains of integrins bind to …?
Alpha chains mediate adhesion by binding to short recognition sequences on ECM molecules such as laminin, fibronectin and collagen.
The integrin cytoplasmic doman is coupled to _____ cytoskeleton.
Actin.
What is Pemphigus and what are symptoms?
Autoimmune disease directed against components of desmosome and hemidesmosome. Epidermal blistering and loss of extracellular fluids
What is Alport’s Sydrome and what are symptoms?
Inherited defect in structure of Type IV collagen.
Symptoms include hematuria
Name 4 functions of microtubules.
- Cell shape
- Organelle movement
- Chromosome movements in cell division
- Cell motility
