IAS19 Flashcards
unit membrane concept & plasma membrane staining
all cellular membranes have same underlying struc. & diff. functions
trilaminar shape, stained by osmium
plasma membrane lipid components structure & movement
PP amphipathic, polar hydrophilic head facing outward, 2 nonpolar phobic tails facing inward
move laterally, rotate or flipflop
cholesterol interspersed among PP, determines fluid nature of membrane (more cholesterol, more interaction w/ FA chain, more rigid)
plasma membrane other components
proteins
integral: part of membrane structure, cannot be removed w/o damaging the membrane
periphery: binds to either side of membrane, can easily be separated
carb: complex glycoproteins
fluid mosaic model
fluidity: PP has high mobility
deg. of fluidity inc. w/ temp (dist. of PP & energy), shorter FA tail, more double bonds, less cholesterol
mosaic: proteins dispersed thruout membrane
plasma membrane functions
C (BIR) SSCC compartmentalization: define boundaries, allows specialized activities to proceed w/o ext. interference & cellular activies to be regulated independently
scaffold for biochem activities
selective permeable barrier: allows some materials to pass but not others, allows nutrients to enter cell & wastes to exit
act as receptors to detect chem signals (trigger cellular activity cascade)
provide contact, adhesion & communication (cytoplasmic process exchange cellular components)
cell membrane permeability
barrier to most water-soluble substances, selective perme. to lipid solvent, high resistance to charged & large molecules
mitochondria & its membrane
provide energy & involved in apoptosis
double membrane: highly folded inner, smooth outer
ER generally
double membrane bound
membrane runs cont. w/ outer membrane of nuclear envelope, lumen cont. w/ nuclear lumen
ER types
rough: flattened sheets of membranes & tubules, ribosomes present for protein synthesis, span through whole cytoplasm, well-developed in protein synth. & secretory cells
proteins synthesized pass on to cisternae
smooth: no ribosomes, more tubular
for lipid synth.; detox in liver; Ca storage & release in muscles
golgi apparatus
for modification, packing & distribution of proteins & lipids for secretion / internal use
stacked membranous, flattened cisternae w/ vesicles
golgi faces & lumen
cis face receives transport vesicles budded from ER containing new proteins
lumen: protein & lipid modification, progression through transport vesicles budding off from each cisterna & fusing w/ the next
trans: mature proteins & lipids released as vesicles, contains condensing granules
lysosome
single membrane bound
contain enzymes to degrade phagocytosed materials
destruction of organelles
peroxisome
smaller ver. of lysosome
contain enzymes to break down long FA & amino acids forming H2O2 byproduct, contains catalase to neut. H2O2
common in liver for detox
nucleus stain & nuclear envelope
stain in H&E: blue / purple (acidic, -vely charge) (cannot see membrane w/ H&E)
envelope: double membrane, pores form by fusion of both membranes
pores allow diffusion of small molecules, active import of proteins & rna from & into nucleus
nucleoplasm
consist of DNA, nucleoproteins, etc.
contains chromatin (DNA & histones)
basophilic, heterogeneously stained
types of chromatin
heterochromatin: dark stained, dense packed chromatin less active at gene transcription, at nuclear periphery
euchromatin: the reverse
nucleolus
synthesis of rRNA, contains genes for encoding rRNA (chr 13 14 15 21 22)
process & assemble ribosomal subunits imported from CP -> transported out of nucleus
nucleolus regions
fc: fibrillar center, palely stained, inactivated genes for transcription
dfc: dense fibrillar component, darkly stained, nascent pre-rRNA transcription, rRNA early modification
gc: granular component, occupies most of nucleolus, ribosomal subunit assembly at diff. stages
cytoskeleton functions
microfilament, intermediate filament, microtubule (extend from centrosome to periphery)
1. maintains cell shape & used in locomotion
2. in cell division
3. guides intracellular traffic of organelles
4. provides mech strength
microfilament & function
actin as building block, globular monomer g-actin polymerize to form long helical filamentous polymer f-actin
polar, + end grows faster than - end
used in muscle contraction, locomotion, cytokinesis & structural functions
microfilament organization & contribution to movement
dynamically organised into bundles & networks, stabilized by interaction w/ diff. cross-linking proteins
some lie in cell cortex below plasma membrane, arranged in loose 3d mesh
in leading edge, microfilaments arranged in ||type bundles, spike-like protrusions formed by active polymerization of actin at tip of protrusion, allows movement & migration
microfilament in cytokinesis
interacts w/ myosin, contracts cells through contractile ring (bundle)
actin assembly in intestinal villi
actin filaments connected by actin-bundling protein fimbrin (CLP)
filaments extend down to apical cytoplasm to form network below microvilli bottom: terminal web, connected to microfilament core
stabilized by CLP filamin
intermediate filament structure
bundled fibrous proteins
2 helical monomers twist to form dimer
2 dimers interact anti|| to form tetramer
tetramers assembled end to end to form protofilament
intermediate filament function
3SA
stronger than actin filament, exhibits strain hardening during stress
-> structural / tension bearing role
maintain cell shape & scaffold to support cell framework
anchor organelles
types of intermediate filament
keratin (epithelial cell), vimentin (connective tissue, smooth muscle), neurofilament (neuron), nuclear lamin (in nuclear lamina in inner nuclear membrane)
keratin filament & defect
forms strong network within cells, connected w/ junctional complexes -> creating sheet of cells allowing to withstand phy force in cells
in mutation (no keratin production) -> cells fragile & prone to rupture in little mech. stress, skin blistering in epidermis & during dermis
microtubules structure
tubulin dimers (alpha, beta tubulin) -> polymerization in linear rows to form protofilament -> 13 protofilaments side-by-side to form hollow center
dynamic: elongation at + end by polymerization, shortening at - end by depolymerization
microtubules origination
microtubule organising center (MTOC)
microtubule assembly initiated & acts as anchor for one end
MTOC called centrosome in animal cell (2 centrioles near nucleus)
MTOC in cilia & flagella called basal bodies, extend microtubules & push out plasma membrane to form cilia / flagella
microtubule in mitosis
forms mitotic spindle to guide segregation of chromosome through shortening & extension
microtubule in IC organelle transport
axonal transport: motor proteins carry chem. components in vesicles down the axon w/ help of microtubules -> released at axonal end to synaptic cleft
kinesin moves toward + end
dyenin moves toward - end
agents that prevent microtubule function
colchicine, bind to microtubules to prevent polymerization
taxol, bind to microtubules to prevent depolymerization -> affect dynamic process of mitotic spindle required for chromosomal separation -> disrupt mitosis & cell division
both act as anti-mitotic drug to prevent cell proliferation
