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Chapter 10A: Cell Architecture I - Coggle Diagram
Chapter 10A: Cell Architecture I
What gives structure and shape to living organisms
Extracellular deposits (lignin, bones)
Extracellular polysaccharide filaments (chitin, cellulose)
Extracellular "jellies" (pectin, glycosaminoglycans)
Extracellular protein fibers (collagen, elastin)
intracellular protein fibers (intermediate filaments, microtubules, microfilaments)
Fibers give strength
"Static fibers" are STABLE
collagen in animal connective tissue
cellulose in cell walls
"Dynamic fibers" can be assembled and disassembled very quickly
Tubulin
Actin
In many connective tissues, composition is mostly extracellular matrix plus a few cells
ex. epidermal layer and meniscal cartilage in knee
DOES NOT rip easily (bears stress of tension and compression)
"Static" fibers outside of cells (animals)
collagen
insoluble, high tensile strength
enriched in tendons, ligaments, cartilage, cornea
secreted by fibroblasts
ECM components are synthesized/secreted by fibroblasts
covalent crosslinks form within a collagen fibril (fibril is a component of a collagen fiber)
proteins within the single fibril are crosslinked together
lack of Vitamin C --> deficiency in collagen crosslinking (scurvy)
vitamin C is the cofactor for many enzymes
fibronectin and laminin (basal lamina)
cell attachment and cues for growth, differentiation, function
elastin
elastic
vascular wall, skin, lung
Cytoskeleton (fibers inside cells)
Cytoskeletal filaments are POLYMERS: fibers are held together by non-covalent linkages
DYNAMIC FIBERS
Actin filaments/microfilaments (smallest)
formed from actin subunits
non-covalently crosslinked actin fibers can be very stable and hold cell shape, generates huge surface area
ex. gut lining
actin fibers rearrangements allow cells to crawl
arrangements: stress fibers, lamellipodia, filopodia
Microtubules (biggest)
made of tubulin
have directionality (plus end and minus end)
(+) end: points OUTWARD in cell
(-) end: points toward cell middle
where cell assembly STARTS
Motor proteins can travel along microtubules (DRAG vesicles)
kinesins travel toward plus end (cell periphery)
dyneins travel towards minus end (centrosome near nucleus)
motor proteins use ATP hydrolysis to crawl along/pull filaments
myosin moves ACTIN filaments, transports vesicles and drives muscle contraction
microtubules are constantly growing and shrinking: "DYNAMIC INSTABILITY"
constnatly exploring the intracellular space
nearly instantaneous adjustments to changes
tracks to where things are needed
dynamic instability allow microtubules to quickly find and attach to chromosomes during cell division
form bundles that can be used to propel cells in cilia and flagella
Rapidly changeable fibers allow ADAPTABILITY
cell movement
ex. macrophage chasing down and engulfing a bacterium
cell shape change
ex. pores (stomata) opening and closing on a leaf
ex. muscle contraction
transportation routes within cell
ex. vesicle delivery to the right place in the cell membrane (following tubulin/actin tracks)
moving cell components
chromosomes during cell division
STABLE FIBERS
Intermediate filaments (length between microtubules and microfilaments)
link together to make a STURDY MESH inside cells
ex. keratin connected to the nuclear lamin
deposited as hair and nails
lots of strands attach together
inside many epithelial cells
defects on intermediate filaments --> human genetic diseases
no connections between cells
ex. rub hands together --> tends to rip (less physically resistant)