Cell junctions and Extracellular matrix

cell junctions

hold multiple celled organisms together

extracellular matrix

glue that holds cells together

cell junctions

hold multiple celled organisms together

extracellular matrix

glue that holds cells together

epithelial tissue

• covering or lining tissue

• has basement membrane

• avascular

• close together = lots of cell to cell junctions

connective tissue

• deep to epithelial

• vascular

• spaced cells

• gaps filled with fibers and ground substance

tight junctions

seals gaps btw epithelial cells

adherens junctions

• connects actin filament bundle in one cell with the next cell

• made of cadherens

desmosome

connects intermediate filaments in one cell to those int he next cell (strong)

gap junctions

• allows passage of small water soluble molecules from cell to cell

• allows for communications btw cells

hemidesmosome

• anchor intermediate filament in cell to extracellular matrix

• EX: epithelial to basal lamina

cadherins

calcium + adhesion

Cadherins movement

• high Ca+ concentration - molecule becomes linear and binds

• lower Ca+ - molecule bends and cant bind

vinculin

can bind a bunch of actin filaments

catenins

link classical cadherins to actin cytoskeleton

how does tension effect adherens junctions

• makes then stronger

• they will form an adhesion belt to connect cadherins to strengthen tissue

tight junctions

• wrap around cells

• series of proteins that make a water proof seal around epithelial cells

tight junction proteins

• claudin

• occludin

example of tight junctions

found in the walls of the stomach and bladder

scaffold proteins

• can bind to claudin and occludin in the cell

• organize junctional protein complexes

gap junctions

• couple cells electrically and metabolically

• big in communication

• physically connect cytoplasm btw cells

gap junction composition

• made of 2 connexon

• 1 connexon is made of 6 connexin subunits

what is the plant equivalent to gap junctions?

plasmodesmata

plasmodesmata

• made by extensions of smooth ER which make holes in the cell wall

selectins

• big in cell to cell contacts

• expressed on surface of blood

• interacts with epithelial cells and sugars to slow down blood by making it leave the blood stream

CAM

call adhesion members

NCAM

neural. expressed in nervous tissue

ICAM

binds to integrins on white blood cells

extracellular matrix

made of proteins and glycosaminoglycan (GAG)

proteoglycan

• made of GAG and core protein

• found in cartilage

Collagen

• made of 3 alpha chains together in a triple helix with glycine facing inwards

Types of collagen

• fiber forming

• fiber associated

• network forming

• transmembrane

• proteoglycan core protein

elastin

• gives tissues their elasticity

• helps pump blood

fibronectin

• binds to integrins

• organize the matrix

basal lamina

made of laminin and type IV collagen

laminin

• made of 3 polypeptides twisted in a T shape

• polypeptides called alpha, beta, and gamma

matrix metalloproteases

breaks down proteins in the matrix and required metal ions to activate

TIMPS

regulates matrix metalloproteases

integrins

• link extracellular matrix to cell/cytoskeleton

• important in basal lamina

• can be regulated (turned on and off)

talin

• tension sensor at cell matrix junctions

• if pulled more vinculin recruited to reinforce the bond with binding actin

cell wall

made from cellulose microfibrils interwoven with a network of pectic polysaccharides

cellulose

• string of glucose with a special link

• pectin - interwoven and cross links cellulose

cellulose synthase

makes cellulose

microtubules

• determines the direction cellulose is laid

• the cellulose direction determines cell elongation