Lec 24, 25 Stem cell and nuclear transfer Flashcards
extracellular matrix
complex network of polysaccharides and proteins secreted by cells. A structural component of tissues that also influences their development and physiology
tissue
cooperative assembly of cells and matrix woven together to forma distinctive multicellular unit with a specific function
importance of the organization of tissues
tissue components have to be properly organized, wtih the right blood vessels, nerves, etc formed inside of them. There has to be functional coordination, many have to be constantly maintained and renewed, and cells have to be replaced in the tight number, and with the right type of cell. disorders in tissue renewal often underlie the development of cancer
cell wall
the structure in plants that supports, encloses, protects, and immobilizes the cells. A mechanically strong fibrous layer deposited outside the plasma membrane. (also present in bacteria, algae, and fungi
cellulose microfibrils
give plant cell walls their strength, these are long, thin polysaccharide fibers. They resist stretching, so their orientation governs the direction in which a growing cell can enlarger, which can control the direction the entire plant is able to grow in.
It is is synthesized on the outside of the cell by enzyme complexes in the plasma membrane. microtubules within the cell controls the shape and modelling of the cellulose fibers
Animal connective tissues
tissues such as bone, tendon, and the dermis. In connective tissues the extracellular matrix is abundant and carries the mechanical load
four types of tissues in animal cells
connective, epithelial, nervous, muscle
collagens
a family of fibrous proteins hat is a major component of the extracellular matrix and connective tissues. They provide tensile strength in animal connective tissues
fibroblasts
cell type that produces the collagen-rich extracellular matrix in connective tissues such as the skin and tendons
integrins
transmembrane proteins that enable cells to make and break attachments to the extracellular matrix, helping them crawl through a tissue
orientation of microtubules on the cytoplasmic side of the plasma membrane
connective
epithelium
sheet of cells covering an external surface or lining an internal body cavity
Different varieties: act as a protective layer, secrete substances, absorb nutrients, detect signals (like light or sound)
types of epithelial cells:
organization of epithelial cells
they are polarized (apical and basal surface) and rest on a basal lamina
Epithelial cell junctions
1) Tight junctions: seal neighboring cells together so that water soluble molecules can’t pass between them, also help preserve the polarity of the cell
2) Cytoskeleton-linked junctions that hold the epithelium together:
a) Adherens and desmosomes bind one epithelial cell to another
b) hemidesmosomes bind epithelial cells to the basal lamina
3) gap junctions: create small water-filled channels across between two membranes
plasmodesmata
cell to cell junction that connects one plant cell to another
tight junctions
totipotency
the ability to produce a fully formed, complex, multicellular organism–resides within a fertilized egg cell
Factors that contribute to the stability of tissue organization:
1) cell communication: each cell monitors signals from its neighbors and adjusts behavior accordingly. This helps make sure that new cells are produced and survive only when they are required
2) selective cell adhesion: different cells types have different binding proteins, so they tend to only stick to cells of the same type, or other things that they have a selective attachment to.
3) cell memory: some types of gene expression are passed on from cell to cell
differentiated cell
cell that has undergone a coordinated change in gene expression, enabling it to perform a specialized function
terminally differentiated cells
many differentiated cell types (ie red blood cells) are no longer able to divide, so they need a steady supply or replacement cells
precursor cells
a stock of proliferating cells that replace terminally differentiated cells
stem cells
relatively undifferentiated, self-renewing cells that produce daughter cells that can either differentiate into more specialized cell types or can retain the developmental potential of the parent cell.
