Cell Biology Flashcards
Describe the findings and hypotheses behind the “sorting out” (differential adhesion) experiments?
- Took neural plate cells and epidermal cells, jumbled them and then they were able to sort out by cell type.
- Repeated with many different types of cells and found similar results
- Differential Adhesion hypothesis = cells sort to be nearer to cells with similar adhesion properties
- Altered Cadherin levels within cells and observed how the cells sorted - those with similar levels were conjugated, higher quantity = centered.
What are cadherins? catenins?
- Cadherins are intermembrane proteins that interact with cadherins of other cells for adhesion
- Catenins - small proteins with 3 subunits that anchor cadherins to the cytoskeleton
What evidence suggests that cadherins are involved in sorting out?
- Mixing cells with p and e cadherins, quantity seems to be the most important factor. When cells have equal quantities of cadherins, proper sorting does not occur.
- Also, if we delete catenins, the cadherins can be “ripped out” of the cell membrane and will not sort properly.
What major cytoskeletal systems are there in cells, what are they made of, and what are their functions?
- Microtubules (tubulin dimers) –
a. important for transportation of cargo throughout the cell, via molecular motors, dynein and kinesin.
b. they important in cell division and structure.
c. They are also important in molecular motors such as in flagella and form the mitotic spindle. - Microfilaments (actin monomers) – Important in cell crawling
- Intermediate Filaments (intermediate filament proteins) – give rigidity to tissues
What is the major cytoskeletal system involved in cell migration?
Microfilaments
How do integrins function in promoting cell migration?
Integrins link the cytoskeleton to other extracellular stuff and provide traction for the cell. They do not link to other cells, as do cadherins.
What is the extracellular matrix (ECM)?
The ECM is a complex of proteins on the outside of the cell that has roles in cell adhesion, cell migration, and epithelial sheet formation
What are the major ECM molecules?
- Collagen
- Proteoglycans
- Specialized Glycoproteins
- Fibronectin
- Laminin
- Integrins
- Basil Lamina
Collagen
Provides strength
Proteoglycans
absorb water and fill space
Fibronectin
cross linker, and can form structures
laminin
structural support, part of the basil lamina
Integrins
transmembrane, link the actin cytoskeleton to the extracellular matrix
Basal Lamina
- laminal layer that can separate two types of cells to serve as a filter, such as in kidneys.
- Layer of the ECM
- Can surround entire cell or be made into a layer under a layer of epithelial cells
- Made of integrins
Three major types of cell signals?
- Endocrine – secreted factors/hormones (act distant)
- Paracrine – secreted diffusible factors (act locally)
- Juxtacrine – ECM membrane proteins interact between cells (cells must be touching)
