36 Questions
What is the primary function of tight junctions in epithelial cells?
To serve as barriers to solute diffusion
What is the role of ZO proteins in tight junctions?
To act as a scaffold
What is the primary function of cadherins in epithelial cells?
To mediate homophilic cell-cell adhesion
What is the role of integrins in epithelial cells?
To mediate heterophilic interactions with the ECM
What is the primary component of the ECM that provides structural support?
Collagen fibers
What is the process by which lymphocytes migrate into tissues?
Mediated by integrins
What is the primary component of ECM produced by fibroblasts?
Collagen fibres
What percentage of skin is composed of collagen?
74%
How many types of collagen proteins exist?
42
What is the sequence found in all collagens?
Gly-Xaa-Yaa
What is the typical structure of an α chain?
A helix with 3 aa per turn
What is the function of proline in collagen?
Stabilizes the triple helix structure
How are collagen polypeptide α chains arranged in a triple helix?
Wound round each other
Where is post-translational modification of collagen chains carried out?
In the ER and extracellularly
What is unique about the structure of matrix proteoglycans and glycosaminoglycans?
They are highly dynamic structures that are continually being produced and remodeled.
Which cells are responsible for secreting matrix macromolecules in connective tissues?
Fibroblasts
What is the primary function of the ECM in connective tissues?
To bear mechanical stresses of tension and compression.
What is the composition of the basal lamina different from?
Connective tissue
What is the primary function of the basal lamina?
To underlie epithelial cell sheets and surround individual muscle cells.
What is the focus of the video series covered in Module 8?
Sorting, matrix, and migration
What is the primary function of the TGN in polarised epithelial cells?
To sort and transport plasma membrane proteins
What is the mechanism of protein transport in the indirect pathway?
Endocytosis and selective transport from basolateral to apical surface
What is the role of lipid rafts in protein transport?
To sort and transport GPI-anchored proteins
What is the function of the cytoplasmic tail of a protein?
To provide sorting signals for protein transport
What is the direction of protein transport in the direct pathway?
From TGN to apical surface
What is the role of the antibody to the cytoplasmic tail of the blue cargo protein?
To isolate transport vesicles
Where do all newly synthesized proteins go first in polarised epithelial cells?
The basolateral surface
Where does endocytosis occur in polarised epithelial cells?
From both the apical and basolateral surfaces
Which type of protein facilitates direct contacts between the ECM and cells via cell surface receptors?
Fibronectin
What is the primary function of integrins in relation to the ECM?
To facilitate interactions between cells and the ECM
What is the role of multiple binding domains in adhesive glycoproteins?
To increase the local protein concentration at the cell surface
Which of the following is a characteristic of adhesive glycoproteins in the ECM?
They contain multiple binding domains
What is the role of actin cytoskeleton in the formation of integrin-ECM interactions?
To generate the tension needed for binding and oligomerization
Which of the following ECM components is involved in the formation of direct contacts between the ECM and cells?
Fibronectin
What is the role of integrins in the migration of lymphocytes into tissues?
To facilitate interactions between lymphocytes and the ECM
What is the function of fibronectin and laminin in the ECM?
To form direct contacts between the ECM and cells
Study Notes
Experimental Rationales for Sorting Mechanisms in Epithelial Cells
- Experimental approaches to distinguish different sorting mechanisms in epithelial cells involve understanding how membrane proteins reach the correct surface of polarized epithelial cells.
- Two pathways exist: direct sorting of membrane proteins in the TGN (Trans-Golgi Network) and indirect sorting via endocytosis and selective transport to the apical surface.
Integrating Cells into Organized Tissues
- The extracellular matrix (ECM) plays a crucial role in integrating cells into organized tissues.
- The ECM is made and oriented by the cells within it, bearing mechanical stresses of tension and compression.
Extracellular Matrix (ECM)
- The ECM is a highly dynamic structure continually produced and remodeled.
- The ECM composition of basal laminae is different from connective tissue.
- The ECM is made up of various components, including collagen, proteoglycans, and glycosaminoglycans.
Collagen and Collagen Fibres
- Collagen is a major fibrillar component of the ECM, found in various tissues such as cartilage, cornea, bone, and skin.
- There are 42 types of collagen, all containing the Gly-Xaa-Yaa-sequon in tandem (10-90% of sequence).
- Collagen has a triple helix structure, with three collagen polypeptide α chains wound around each other.
- Proline stabilizes the helical conformation, while glycine fits into the crowded interior, allowing tight packing of the triple helix.
Adhesive Glycoproteins of the ECM
- Adhesive ECM glycoproteins, such as fibronectin and laminin, form direct contacts between the ECM and cells via cell surface receptors (integrins).
- These glycoproteins contain multiple binding domains and interact with cell surface receptors, localizing fibronectin/laminin at appropriate sites for assembly and increasing local protein concentration at the cell surface.
Cell-Cell Adhesion and Integrins
- Cadherins mediate homophilic cell-cell adhesion, with a specific structure and molecular interactions.
- Integrins mediate heterophilic interactions between cells and the ECM, with a specific structure, molecular interactions, and regulation.
- Integrins play a crucial role in lymphocyte migration into tissues.
This quiz covers the structure and function of collagens, the major fibrillar components of the extracellular matrix (ECM). It includes the production of collagens by fibroblasts and the secretion of these large molecules.
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