Chapter 15 Flashcards
Function of extracellular matrix?
provides structural support to cells and tissues and regulates cell bahviour
cell wall function?
determines cell shape and prevents cells from swelling and bursting
bacterial cell wall shapes ?
rod shaped, spherical, spiral shaped
two classes of bacteria?
gram positive and gram negative bacteria
difference b/w gram positive and negative bacteria?
gram-ve=thin cell wall
gram+ve=thick cell wall
main component of bacterial cell wall?
peptidoglycan
FtZ
cell division
MreB
cell elongation
main component of cell walls of eukaryotes?
polysaccharides
fungal cell walls and exoskeletons of anthropoids?
chitin
what is the cell wall of algae and higher plants made of ?
cellulose
what are the linkages between chitin and cellulose ?
beta 1—>4 linkages
highly branched polysaccharides H bonded to the surface of cellulose microfibrils, provide stability and mechanical strength ??
hemicellulose
branched polysaccharides with negatively charged galacturonic acids?
pectins(cross link cellulose microfibrils)
primary cell walls?
thin, flexible , contain equal amounts of cellulose, hemicellulose and pectins
secondary cell walls?
1-present b/w plasma membrane and primary cell wall after cell growth
2-lack pectin and are50-80% cellulose
are complex polymer of phenolic residues that gives strength and density to wood?
lignin
do cells maintain osmotic balance between the cytosol and extracellular fluids?
no
what builds up in the cell and eventually equalizes the osmotic pressure and prevents further influx of water and leads to rigidity of plant tissues ?
hydrostatic pressure/turgor pressure
which plant hormones activate proteins called expansins which weaken the Reginas of the cell wall allowing expansion?
auxins
where does all the water accumulate so the cell can’t expand without increasing the volume of the cytosol?
large central vacuole
what enzyme synthesizes cellulose from UDP glucose ?
cellulose synthase
what are laid down parallel to cortical microtubules under the plasma membrane?
microfibrils
what guides the movement of cellulose synthase and defines the orientation of the newly synthesized microfibrils?
microtubules
what defines the direction of cell wall growth and cell expansion and ultimately the shape of the entire plant ?
cortical microtubules
thin layers on which epithelial cells rest and surround muscle cells, dispose cells and peripheral cells ?
basal laminae
where is extracellular matrix most abundant ?
connective tissue
tendons?
high proportion of fibrous proteins
cartilage?
high level of polysacchrides
bone matrix?
calcium phosphate crystals
the major structural protein?
collagen
what is collagen made up of ?
triple helices(three polypeptide chains)
smallest amino acid?
glycine
what does the triple helix domains amino acid sequence consist of?
Guy-X-Y
what is formed in the ER by modification of proline in collagen polypeptide chains?
hydroxyproline
type 1 collagen forms _______ in which the triple helical molecules form regular staggered arrays.
collagen fibrils
procollagens?
assembly of fibrils occurs outside the cell from soluble precursor
what cross links b/w side chains of lysine and hydrooxylysine residues help strengthen the fibrils?
covalent cross links
Fibril associated collagens bind to collagen fibrils and link them to one another and to other matrix components. T/F
True
what type of collagen is basal laminae ?
type IV
what is present in organs that stretch and return to shape such as lungs ?
elastic fibres that are made of elastin
extracellular matrix gels are formed from polysaccharides called _______.
GAGs(glycosaminoglycans)-they are repeating units of disaccharides
what is the only GAG that is a single long polysaccharide chain?
hyaluronan
GAGs link to proteins to form?
proteoglycans
what is the major proteoglycan of cartilage that has about 100 chains of chondroitin sulphate attached to a core protein?
aggrecan
____ link matrix components to one another and to cell surfaces.
matrix adhesion proteins
what is the main adhesion protein of connective tissues?
fibronectin
basal laminae belong to which family?
laminin family
laminas are tightly associated with _____ and adhesion protein that also binds to type IV collagen.
nidogen
transmembrane proteins that attach cells to the extracellular matrix??
integrins
_____ were first identified by immunofluorescence and immunoelctron microscopy of transmembrane glycoproteins at points of cell adhesion to the matrix.
integrins
bundles of actin filaments are anchored to beta subunits of integrins via other proteins??
focal adhesions
they anchor epithelia cells to basal laminae?
hemidesmosomes
name cell adhesion molecules ?
selecting, integrins, immunoglobulin superfamily, cadherins
what do selectins do?
mediate transient interactions b/w leukocytes and endothelial cells
____ leave the circulation at sites of tissue inflammation by interacting with endothelial cells of capillaries.
leukocytes
example of heterophilic interaction?
binding of ICAMS to integrins
heterophilic interaction?
an adhesion molecule on one cell recognizes a different molecule on another cell
homophilic interactions ?
adhesion molecule on one cell binds to the same molecule on another cell
what links actin filaments of adjacent cells ?
adherens junctions
what links intermediate filament cytoskeletons of adjacent cells ?
desmosomes
____ in epithelial cell sheets from a seal that prevents free passage of molecules and ions b/w cells.
tight junctions
what acts as a glue to hold adjacent cells together?
middle lamella
adjacent plant cells communicate through cytoplasmic connections called?
plasmodesmata
