Cell Bio - Cell adhesion and signalling Flashcards
difference between planktonic and sessile bacteria
planktonic - freely existing in bulk solution
sessile - attached to a surface or within a biofilm
what does the extracellular matrix (ECM) consist of
network of proteins and polysaccharide chains that are manufactured by cells, secreted and modified outside the cell by several different enzymes.
what are the functions of the ECM
mechanical - tensile and compressive strength and elasticity
protection - buffering against extracellular changes and water retention
organisation - control of cell behaviour by binding of growth factors and interactions with cell surfaces
what secretes the matrix macromolecules
fibroblasts
what forms bones and cartilage
bones - osteoblasts
cartilage - chondroblasts
what are the main macromolecular components of the ECM
glycosaminoglycans
fibrous protein
non-collagen glycoprotein
structure of glycosaminoglycans (GAG)
GAGs are unbranched polymers of repeated disaccharide derivatives, including amino sugars, sulfated acetylamino sugars and uronic acids
what are the properties of GAG’s
Acidic and negatively charged
Attract positive ions (eg Na+) which attracts water causing gel formation
Comprise 10% of ECM mass but 90% of volume
GAGs (especially hyaluronan) provide compressive strength
Metabolically cheap bulking agent
what is hyaluronan
GAG
107kDa
spun out of the cell membrane
function of hyaluronan
used to hold together open spaces in the ECM that would otherwise be filled up with cells
structure of a proteoglycan
serine-rich protein decorated with hundreds of O-linked acidic or sulfated GAG’s
what is aggrecan
common proteoglycan in the ECM
Its core protein is decorated with around 100 chondroitin and 30 keratan chains.
what does aggrecan bind to
hyaluronan via adaptor proteins
what is the function of the primary cell wall in plants
flexibility allowing expansion and remodelling
composition of the primary cell wall
cellulose
hemicellulose
pectin
function of the secondary cell wall
rigid providing strength
composition of secondary cell wall
cellulose
hemicellulose
lignin
what accounts for 20% of primary cell wall dry weight
xyloglucan
what is the backbone of xyloglucan composed of
1,4-linked β-D-Glcp residues
what occurs to 1,4-linked β-D-Glcp residues
are substituted at O6 with mono-, di-, or triglycosyl side chains.
where does galacturonic acid occur (Gala)
homogalacturonan (HG)
rhamnogalacturonan (RG)
function of pectin demethylase
demethylates pectin
makes it available for crosslinking via Ca2+ bridges
what is an occluding junction
seals cells together forming an impermeable barrier
anchoring junctions
attaches cells to other cells or the ECM
communicating junctions
allows exchange of chemical/electrical information between cells
function of adheren junctions
important role in determining shape of multicellular structures
forms an indirect link between actin cytoskeletons
what do adhesion belts allow
reshaping of epithelial cells
form vesicles
function of desmosome junctions
indirectly link intermediate cytoskeletons
provides mechanical strength