Cell junctinos are interactions between what?

(2 examples)

cells and a substratum (ECM)

or between cells

1. adhesive junction- link cells together or cells to extra cellular matrix

2. tight junctions- link cells together

3. gap junctions- provide cell-to-cell communication

procide strcutral integrity,

resist stress,

allow connected cells to form as a "unit"

Desomeoms form during ealy embyronic development

and maintain cell positioning therafter

homophilic

(which means:)

binds identical cadherins on the surface of an adjacent cell

1. small cytoplasmic region which associtaes with plaque regions

2. single TMD

3. large extracellular region that includes several repeat domains

interceullular- between cells (equivalent to the extracellular space)

intracellular- within a cell

used to observe the innner surface of the plasma membrane bilayer leaflet

can observe 'ridiges' foremd by paired rows of aligned integral membrane protiens.

it is a polarized cell with different functional domains in the plamsma membrane

Na/glucose pump in the apical pm

cell to cell junctional protiens in the lateral pm.

two pm from adjacent cells joined by tightly packed hollow cylinders/particles called connexons (7 nm diameter)

cylainders alighed forming direct hydrophilic channels between the opposing cells

5-1000 connexons per gap junction plaque

Circular assembly of six identical intergral membrane protein subunits- connexins

Which of the following strucutures help form the blood brain barrier by restricting the movement of extraceulluar material between adjacent cells?

a) gap junctions

b) tight junctions

c) desmosomes

d) focal adhesion

e) adherens junction

desmoplakin and plakoglobin

bind to cadherins and tonofilaments

small cytoplasmic domain

single TMD

large exracellular domain

occludins and claudins

are transmembrane junctional proteins.

[Ca²⁺ ]  which mediates the conformational changes in connexin subunits

1. provide rigidity/strength- maintain cell shape and allow cells to withstand turgor pressures

2. extracellular metabolsim- site of cell wall enzymes

3.protection from pathogens (mechanical injuries)

4.mediate cell to cell interaction/adhesion and signaling between cells

5. serve as a permeability barrier- gases, water, ions, hormones, surgar, and amino acids diffuese freely thrhough cell walls.

1. structual proteins- cellulse fibrils- rigid, fiber like shape (provide strength). like collagen and elastin in ECM
2. polysaccharides- pectins- a matrix in which structural proteins and adhesive molecules are embedded. like proteoglycans in ECM
3. adhesive molecules- hemicellulose (branched polysaccharides) extensins (glycoproteins). like fibronectins and laminins in ECM.

All surgarsr are negatively cahrged.

They bind/trap wter molecules to yield matrix with gel like to very rigid consisentcy

1. cell adhesion - cross-linking to other pectins and other cell wall components and thus allows adjacent cell walls to bind together

2. determine cell wall porosity- increase in pectins means decrease in porosity of cell wall

3. pectin fragments serve as signialing molecules when cell wall is damaged physically by a pathogen- initate a plant defence responce (via receptor at plasma membrane)

4. gel-forming capacity- add pectins to fruit juice to make jams and jellies

Glycoprotein's poly peptide chain is rich in?

Describe how this amino acid bind to pectin molecules.

True of False

are all the various compents sectreted from cell at pm into the extraceullar space at random?

False

all of the various componetns secreted from cell at pm into the extracelllular spaceu in a coordinated,stepwise manor.

ER - extensins and other cell wall proteins

Golgi- pectins, hemicellulose, and protein modifications (such as sugar additions to extensins)

plasma membrane- cellulose

the middle lamella

composed of mostly "sticky" pectin (matrix polysaccharide)

the Primary cell wall

forms while cells are still growing

new microfibrils are depostied outside of the cell- in the extracellular space

new microfirils are thne 'anchord' (connected) to other cell wall components.

secondary cell wall.

occurs in only certain plant cells that require a thicker, more rigid cell wall.

The secondary cell wall consitst of how many layers of cellulose?

Each layer consisting of bundles of microfibrils arranged in paralel to from?

three layers

larger macrofibrils

desmotubule- tubular membrane strucutre loacted within the channel opening

annulus- ring of cytosol continuous between adjacent cells, and servers as a 'filter' to allow only small molecules to pass through from cell to cell

protein particles- globular and spoke-shaped protiens attached to pm and desmotuble membrane

1. structural support
2. postion membrane bound organeels wihtin the cytosol
3. serve as 'highways' for movement of materials to specific parts of the cell
4. cell movement
5. cell division

single celled- movement 'crawling' due to changes in teh cell shape or specialzed locomostion organelles

multi-cellular- certain cells capable of idnependent movement/locaomtion; skeletal muscle contration- due to sliding of actin filiaments

contctile ring is in animal cell and consists of actin microfilament that encricle the cell and serve to physciall "pinch" the cell in two,

while the phragmoplast is in plant cells and consists of actin microfilaments and microtubules and serves in building (positioning) a new cell wal between the separated nuclei of a dividing cell

microtubles (MTs)

microfilaments (MFs)

intermediate filaments (IFs)

microtubles- tubulin

microfilaments- actin

intermediate filaments- keratin

1. axonemal MTs- highly organized, stable found in subceullualr strucutres assoicated with cell movement

2. cytoplasmic MTs- loosely organized dynamic network loacted throughout the cytosol  (orgniazes cell shape, orientation of cellulose microfibrils, chromosome movement, cellular highway)