chapter 11 cell-cell interactions

laminins

ECM crosslinking proteins not to be confused with laminas

ECM and cytoskeleton are directly linked

ECM strengthened by connections to transmembrane proteins actin protein filaments in the cytoskeleton bind to intern proteins integrins bin to ECM proteins such as fibroconectins and laminas

cell walls in plants

all plants cells are surrounded by cell wall- fiber component that is the basis for paper, thread, wood.

gap junctions does what (vague)

allow a lot of signaling between cells

fundamentals of cell adhesion proteins

anchor in the plasma membrane form selective attachments w other adhesive proteins on surface of adjacent cells linked to cytoskeleton

2 classes where hormones are received

at plasma membrane inside the cell

intern proteins

bind to ECM proteins including laminins which in turn bind to other components of ECM

microfibrils

bundles of cellulose strands "steel rods"

how do cells communicate with each other?

cell cell gaps

reception (vague)

cell picking up hormones

selective adhesion

cells adhering to other cells of the same tissue type

proteoglycan

composed of a core protein and glycans- sugar part (polysaccharides) used to help absorb water veyr hydrophilic

epithelial tissue

composed of sheets of cells cover organs line body cavities

extracellular layer composed of

cross linked network of long fibers (rods) embedded in stiff surrounding materials

our cells have defined shape, how is this achieved?

cytoskeleton but ALSO -extracellular layer

cell cell gaps/ gap junctions

direct connections (pores) between cells in a tissue allows cells to communicate work together only works with cells that are right next to each other

where does collagen get wound to be secreted?

endoplasmic reticiulum (ER)

connections between animal cells

epithelial tissue

although animal cells DO NOT make a cell wall, they do form a fiber composite outside their PM called

extracellular matrix

the combination of compression and tension resistant elements ________

fiber composites of cell wall are particularly rugged.

animal tissues have gap junctions that connect cells by

forming channels channels allow the flow of small molecules between cells

plasmodesmata

gaps in cell wall where pm, cytoplasm, and smooth ER of two cells connect

turgor pressure

helps hold the plant upright in a turgid cell: water enters by osmosis vacuoles swells and pushes against cell wall forces plant upright/structure

fibroconectins

high molecular weight glycoprotein of the ECM that binds to receptors called integrins

how do distant cells communicate?

hormones

characteristics of gelatinous polysaccharides

hydrophilic, keeps cell moist gelatinous components are synthesized through rough ER and Golgi and are secreted into extracellular space

enzyme linked receptors

tigger the activation of a series of proteins inside cell

cell-cell attachments

tight junctions desmosomes gap junctions

cells must be attached but also communicate

tight junctions seal cells together desmosomes connect the cytoskeletons of cells gap junctions act as channels between cells

fundamental problem: collagen is ________ to fit into a transport vesicle how is larger cargo like collagen accommodated in vesicles?

too big coat forms on top and then long proteins come down to accommodate rest of the collagen

lipid insoluble signals require

transduction- amplifies signal signal reception signal transduction signal amplification signal response

signal deactivation (step 4)

turning off signal is just as important as turning it one cells have automatic and rapid mechanisms for signal deactivation mechanisms allow the cell to remain sensitive to small changes in: concentration of hormone number and activity of signal receptors

selective adhesion in sponges sponge experiment

two sponges of diff species use chemical treatment to disassociate cells mix cells from two species hypoth: cells of same will adhere to each other results: cells of the same type have specific adhesion molecules or mechanisms

signal response (step 3 cell cell signaling)

ultimate response to cell cell signal varies but can: change which genes are being expressed in the target cell activate or deactivate a particular target protein that already exists in the cell

flaccid cell

water lost from cell, vacuole shrinks, cell loses shape

(plant cell wall) hydrophilic gelatinous polysaccharides are

"filler molecule" long chains of sugars linked together fills in between cellulose rods and helps form rigidity keeps the cell wall moist example- pectin: added to jam to thicken it

collagen means

"glue producing" 3 polypeptide chains wound around one another to form a fibril 1.5 nm

many types of structures connect epithelial tissue

- Tight junctions - Desmosomes

tissues are comprised of

-Groups of similar cells - Performing similar functions

expansins

-young plant cells secrete this protein into their cell wall. -expansions disrupt the H bonds that cross link the microfibrils in the cell wall, allowing them to slide past one another -turgor pressure forces the wall to elongate and expand, this results in cell growth

what percent of your body is collagen?

35% tendons ligaments skin makes skin more firm

what does signal reception look like? steroid

PM signal arrival- steroid hormone receptor in cytosol signal reception nucleus- direct signal response targets DNA

lignin

a complex polymer that forms a rigid network

ECM consists of

a ground substance of gelatinous polysaccharide a network of protein fiber * most common ECM protein fiber is collagen

kinase cascade to activate final response

a protein kinase is activated phosphorylation cascade results

g proteins

activated when dined to GTP deactivate when they hydrolyze the bound gtp to gdp trigger production of intracellular messenger

protein kinases

add a phosphate group to other proteins phosphorylation

animal cells attach selectively because

adhesion proteins different cell types have different adhesion proteins

cadherins

adhesion proteins in desmosomes

do animal cells have adhesion proteins on their surfaces? experiment

hypoth: selective adhesion is due to specific membrane proteins 1.isolate membrane proteins 2.produce antibodies 3.treat cells with antibodies and observe results/conclusion the protein that was blocked in experiment 2 (cadherin) is involved in cell cell adhesion

primary cell wall (plant cell wall) *compare primary cell wall in plant vs animal (possible test question)

in new plants, is composed of -long strands cellulose -bundled into microfibrils these two things form a crisscrossed network clearly seen on electron micrograph

laminas

intermediate filaments found in the nucleus

signal transduction

involved G proteins or enzyme linked receptors amplifies signal

direct linkage between the cytoskeleton and ECM

keeps individual cells in place helps adjacent cells adhere to each other breakdown can lead to metastasis of cancerous cells

collagen is ____ rigid than _____ in the plant cell wall

less rigid than cellulose collagen is more elastic

desmosomes

link the cytoskeletons of adjacent cells with intermediate filaments easily seen on electron micrograph

hormone

long distant messenger that carries info secreted from a cell circulates in body act on target cells far from the signaling cells

cellulose

long rigid structural component in cell wall that bundles together

function and chemical structure of hormones vary widely

may or may not be able to get across the membrane

the extracellular matrix (animals)

meshwork surrounding (directly attached) outside of cell fiber composite secreted in all cells provides structural support varies depending on cell type

microfibrils are cross linked with

other polysaccharide filaments called pectins

plASMA MEMBRANE

phospholipid bilayer with embedded proteins -may be integral or peripheral proteins the boundary of life (in and outside of cell) selectively permeable and controls flow of materials in and out of the cell

multicellularity

physical connections between cells

plants have special gap junction/ cell cell gap

plasmodesmata

SECONDARY PLANT CELL WALL (difference between plant and animal)

polysaccharide secreted between PM and primary cell wall structure varies from cell to cell depending on that cells function in cells that form wood, the secondary cell wall contains lignin

several second messengers work by activating

protein kinases

ECM ground substance (gelatinous polysaccharide) is ______

proteoglycans (the gel) compared to pectin in plant cell

cell-cell signaling

reception transduction response and desensitization

2012 nobel prize in chemistry

robert lefkowitz and brian kobilka

as plant cells mature and stop growing they may secrete an extra layer of material called

secondary cell wall

cell cell signaling occurs in 4 steps******

signal reception signal processing signal response signal deactivation

signal reception

signal receptors are bound by hormones and other cell cell signals identical receptions in diverse cells allow long distance signals to coordinate the activities

second messengers

small molecules diffuse rapidly throughout the cell amplify hormone signal

hormones are usually

small moles present in small concentrations have a large impact on organism as a whole

cells of multicellular organisms _____

stick to one another have specific distinct structure and function

ECM helps cells

stick together form protein-protein attachments link ECM directly to the cells cytoskeleton

tight junctions

stitch the two cells together to form a watertight seal clearly seen in electron micrograph

cell walls vs extracellular matrix

structure and function of cells cell wall for plants extracellular matrix for animal cells

extracellular layer

structure forms just outside the plasma membrane fiber composite -a cross linked network of strong filaments -surrounded by stuff ground substance helps define cells shape and either attaches it to another cell or acts like a defense against the outside world

plant also have hormones

they also have to respond from far way