IAS19

Question 1

unit membrane concept & plasma membrane staining

Answer 1

all cellular membranes have same underlying struc. & diff. functions
trilaminar shape, stained by osmium

Question 2

plasma membrane components & movement

Answer 2

PP amphipathic, polar hydrophilic head facing outward, nonpolar phobic tail facing inward, held tgt by hydrophobic interactions
move laterally, rotate or flipflop
cholesterol interspersed among PP, determines fluid nature of membrane (more cholesterol, more interaction w/ FA chain, more rigid)

Question 3

fluid mosaic model

Answer 3

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

Question 4

plasma membrane functions

Answer 4

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:
barrier to most water-soluble substances, selective perme. to lipid solvent, high resistance to charged & large molecules
act as receptors to detect chem signals (trigger cellular activity cascade)
provide contact, adhesion & communication (cytoplasmic process exchange cellular components)

Question 5

mitochondria & its membrane

Answer 5

provide energy & involved in apoptosis
double membrane: highly folded inner, smooth outer

Question 6

ER generally

Answer 6

double membrane bound
membrane runs cont. w/ outer membrane of nuclear envelope, lumen cont. w/ nuclear lumen

Question 7

ER types

Answer 7

rough: flattened sheets of membranes & tubules, ribosomes present for protein synthesis, 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

Question 8

golgi apparatus

Answer 8

for modification, packing & distribution of proteins & lipids for secretion / internal use
stacked membranous, flattened cisternae w/ vesicles
cis face receives 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

Question 9

lysosome

Answer 9

single membrane bound
contain enzymes to degrade phagocytosed materials
destruction of organelles

Question 10

peroxisome

Answer 10

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

Question 11

nucleus stain & nuclear envelope

Answer 11

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

Question 12

nucleoplasm

Answer 12

consist of DNA, nucleoproteins, etc.
contains chromatin (DNA & histones)
H&E staining dark purple (basophilic)
heterogeneously stained

Question 13

types of chromatin

Answer 13

heterochromatin: dark stained, dense packed chromatin less active at gene transcription, at nuclear periphery
euchromatin: the reverse

Question 14

nucleolus

Answer 14

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

Question 15

nucleolus regions

Answer 15

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

Question 16

cytoskeleton functions & types

Answer 16

microfilament, intermediate filament, microtubule (extend from centrosome to periphery)
1. maintains cell shape & used in locomotion
2. in cytokinesis
3. guides intracellular traffic organelles
4. provides mech strength

Question 17

microfilament & function

Answer 17

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 & structural functions

Question 18

microfilament organization & contribution to movement

Answer 18

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

Question 19

microfilament in cytokinesis

Answer 19

interacts w/ myosin, contracts cells through contractile ring (bundle)

Question 20

actin assembly in intestinal villi

Answer 20

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

Question 21

intermediate filament structure

Answer 21

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

Question 22

intermediate filament function

Answer 22

stronger than actin filament, exhibits strain hardening during stress
-> structural / tension bearing role
maintain cell shape & scaffold to support cell framework
anchor organelles

Question 23

types of intermediate filament

Answer 23

keratin (epithelial cell), vimentin (connective tissue, smooth muscle), neurofilament (neuron), nuclear lamin (in nuclear lamina in inner nuclear membrane)

Question 24

keratin filament

Answer 24

forms strong network within cells, connected w/ junctional complexes -> creating sheet of cells allowing resistant mechanical stress
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

Question 25

microtubules structure

Answer 25

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

Question 26

microtubules origination

Answer 26

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

Question 27

microtubule in mitosis

Answer 27

forms mitotic spindle to guide segregation of chromosome
microtubules attach to centromere -> shortening & extension brings chromosomes to epipolar membrane

Question 28

microtubule in IC organelle transport

Answer 28

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

Question 29

agents that prevent microtubule function

Answer 29

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