Cell Surface and ECM

Cell surface

the outer boundary of a cell

plasma membranes

regulates entry and exit of materials, supports communication, and anchors to the cytoskeleton

cell wall

gives structure and protection to plants, fungi, and bacteria

Cell surface proteins

act as receptors, enzymes, adhesion molecules, and identifiers

glycolipids

lipid with carbohydrate chains; important for cell recognition and adhesion

cytoskeleton

network of proteins inside the cell providing support and shape

cell wall

rigid outer layer (plants, fungi, and bacteria) for structure and defense

extracellular matrix

network outside the cell that aids in adhesion and signaling

Surface area to volume ratio

small cells have a larger surface area compared to volume

SA:V decreases

as cells grow, ___________, limiting diffusionand efficiency

advantage of high SA:V

fast diffusion

active metabolism

efficient growth and thermoregulation

Cellular adaptations

modified shapes

specialized organelles

complex transport systems

Intercellular junctions

cells interact and communicate via ________ differing between plants and animals

plasmodesmata

channels through plant cell walls that connect cytoplasm between adjacent cells

tight junctions

impermeable seal

adherence junctions

strong adhesion

gap junction

direct communication between neighboring cells

desmosomes

composed of cadherin proteins linked to intermediate filaments

Cadherins

calcium-dependent adhesion molecules at cell to cell junctions

structure of cadherins

repeats

transmembrane domains

cytosolic tail

ECM of animal cells

complex network of proteins and carbohydrates located outside the plasma membrane

colagen

most abundant ECM protein, provides tensile strength

elastin

provides elasticity; allows tissues to stretch and recoil

fibronectin

glycoprotein linking integrins (receptorrs) to collagen; guides cell adhesion and migration

laminin

found in basal lamina; supports adhesion, differentiation, and migration

GAGs

long, unbranched polysaccharides

Proteoglycans

core proteins with GAG chains attached; regulate signaling and cushion tissues

basal lamina

thin ECM sheet under epithelial tissues

precollagen peptidase

removes terminal peptides outside the cell

Plasma fibronectin

helps attach platelets to fibrin during clot formation

ECM normal roles

development, angiogenesis, and immune function

cancer

altered ECM composition promotes tumor growth and metastasis

fibrosis

overproduction of collagen leads to tissue scarring and organ failure

arthritis

breakdown of ECM in cartilage causes joint damage

genetic disorders

collagen mutation cause Ehlers-Danlos syndrome (weak connective tissues