ch 11: cell-cell interactions Flashcards
what is the purpose of an extracellular layer of molecules?
provides structure and withstands tension and compression
what is the structure of the extracellular layer?
cross-linked network of long filaments of biomolecules embedded in a stiff surrounding material
how many layers to plants have to their cell walls, and what are their names?
- primary cell wall
- secondary cell wall
- middle lamella
what does the primary cell wall consist of?
cellulose and pectin
purpose of cellulose in the primary cell wall
provides structure and allows the cell to maintain its shape
how is the cellulose arranged?
in a crosshatch network (multiple layers)
pectin
gelatinious substance that keeps the cell wall moist
what are expansins?
they disrupt the hydrogen bonds in the primary cell wall to allow the cell to grow
what does cell expansion require?
constant rearrangement of bonds in the polysaccharide network
how is the secondary cell wall created?
mature plants secrete molecules to form it
where is the secondary cell wall located?
between the plasma membrane and primary cell wall
what is the secondary cell wall made of?
in leaves: waxes that protect against losing gases and water
in wood: lignin that withstands gravity and wind
in animal cells, what is their extracellular matrix made of?
proteins, glycoproteins, and proteoglycans
what does the extracellular matrix assemble into?
collagen or proteoglycans
collagen
glycoprotein that is a strong rope-like fibers
- more protein than carbohydrate
proteoglycans
gelatinous networks
- more carbohydrate than protein
middle lamella
made of gelatinous pectins and is continuous with the primary cell wall
what is the purpose of the middle lamella?
connects adjacent plant cells
what are the 2 types of membrane proteins connecting animal cells?
- anchoring or joining junction
- communicating junctions
what are the 2 types of anchoring/joining junctions?
desmosomes and tight junctions
what is the communicating junction called?
gap junctions
tight junctions
make water-tight seals that do NOT allow for transport
how do tight junctions form?
membrane proteins of adjacent cells bind to each other
desmosomes
provide stability, flexibility and secure adhesion
how do desmosomes form?
by anchoring adhesion proteins at the plasma membrane to the cytoskeleton of two adjacent cells
gap junctions
create continuous cytoplasms that allows water, ions, and small molecules (amino acids/nucleotides) to pass freely down their concentration gradient
are gap junctions specific?
no, it is just based on whether they can fit through the gap junction
do plants have gap junctions?
no
what do plants have in place of gap junctions?
plasmodesmata
plasmodesmata
communication channels between cells through cell walls
what organelle are the plasmodesmata connected by?
the smooth er of two different cells
how is transport allowed through the plasmodesmata?
the smooth er is surrounded by a phospholipid bilayer that allows molecules through
why are antibodies used to understand cell adhesion?
it shows that specific proteins on the cell surface of the tissue are involved in cell-cell adhesion
