L5 Cell ultrastruc

Question 1

LO2: expl why EM capab of finer resol than LM.

Answer 1

-lim resol prop to wl- resol incr as wl decr.
LM uses visb light wl 0.4 violet to 0.7 deep red. theroetic lim resol 0.2um while bact are 0.5um.
EM use e-. wl at 100000V accel= 0.004nm. smaller lim resol. SEM lim approx 10nm, TEM predic lim 2nm for biol specim. theroet lim 0.002nm.

Question 2

LO3: simp diag of cell, ultrastruc compon euk.

Answer 2

• endos, PM, golgi, peroxisome, cytosol, lysos, rer, muc, free polyribos, mito.
• prok no int mem, boichem procs compart. euk complex.

Question 3

LO4: how cell funcs by desc struc and func of cell compons and organelles:

Answer 3

…..

Question 4

MEM:

Answer 4

-Plip bilay in aq sol. amphipathic. rel imperm barr to water sol molecs. prots diss in bilay med funcs, some freely mob some att to cytoskel, tight junc stops leaving apical, phob part spans mem, often alpha helix.
-phillic head= choline-P-glycerol
phob tail 2x fa, cis doub bond=kink.
-cell coat/glycocalyx made of oligo and polysacc s/c on outs pm. att tp lip or prot. sug=specif. ruthenium red stains. often Rs trigg casc.

Question 5

PM.

Answer 5

• outer bound of cell. 9nm. gp and gl projec outw=glycocalyx.
• funcs: selec perm, transp mater along surf, endoc/exoc, intercell adhes and recog, sig transduc, compartm.

Question 6

ER:

Answer 6

• inside plasma netw. interconnec mems, vesics and cisternae, prob contin through cytop, encloses 1 lumen.
• RER- ribos att outer surf, lot in cell activ synth prot. ribos gen prot assoc with rer and destined for cell ext/lysos/cell mem incorp. ent cist space 1st. free ribos in cytop synth prot for cytosol.
• SER- no ribos. cisternae not as flat. us levs extens, scatt rnd cytop. func main lip biosynth and intracell transp eg steroid prod. in liv, mammary gl, ovary, testis, adren gl ster.

Question 7

LO1: define lim of resol.

Answer 7

• min dist at which 2 obj can be disting.

Question 8

GOLGI:

Answer 8

-stacks cisternae. vesics bud off rer, fuse convex cis face, mig to concave by bud and fuse.
FUNC: sort, conc, pack, modif prots synth by rer. eg glycosylat. pack in vesics- leave concave face to lysos or sec. sec vesics often condense (sec grans) and rel conetents at cell surf by exoc.
sig med divers to lysos. constant constit sec. sig med div to sec vesics for reg sec eg dig enzs.

Question 9

LYSOS:

Answer 9

-cont ac hydrolases pH 5. 40 hydrolytic enzs- nuclease, protease, glycosidase, lipase, Pase, sulphatase, Plipase. gen by golgi. 0.05-0.5um. lysos mem v glyosyl to protec mem. fixat prevs hydrolase esc and destr cell.
div shape- us dense spheric.oval. prim lysos id by enz content. prim fuse endocytosed mem bound vesics (phagos, endos), with autophagos (defunct organelles encirc by er), or with excess sec prod to form secondary lysos ( dig vacuoles eg phagolysos) in which contents deg. indig remn= resid bods.

Question 10

PEROXISOME:

Answer 10

-approx spheric. cont gran ma. sing mem. self replic, no genome of own. in all cells esp kidney tubules and liv parenchymal which detox to molecs in blood eg alc, phenols, formic ac, formald.
maj sites O util and h2o2 prod. catalases use h2o2 gen to oxid other S (above). half alc cons oxid to acetald by h2o2 to h2o.

Question 11

MITO:

Answer 11

-spheric/elong oval. 2x mem, inner folded to cristae us lamellar (tubul in ster synth).
FUNC: gen atp by oxid P. main S gluc and fa. ma conts enzs of TCA and fa cyc, D+RNA, ribos, Ca grans. inner mem- enzs for oxid reacs of ETC, imperm to small ions. outer mem perm to all molec under 5000Da. atp synthase inner mem. lot in liv and skel musc. 2000 per liv cell. wrap sperm tail.
has own genet info. dna, ribos, and div simil to bact, thought ori bact dev symb with primord euk. fem lineage, trace few wom.

Question 12

CYTOSKEL:

Answer 12

in all cells. maint/change shape. struc supp PM and organelles. movem organelles/PM/cytos constit. locom-amoeboid/flag/cilia, contractility eg musc.

• microfilam- 5-9nm. main cortic distrib. 2 twisted actin strings. dynam canassemb/disass. often edge epith. assoc atp (contractile). eg core of actin filam mvilli shape.
• intermed- 10nm. comm in epith. not dynam. tough supp netw cytop. also beneath inn nuc mem-nuc lamina. eg keratin, vimentin. comm in nerve and neuroglial cells. also epith where made of cytokeratin, form supp mesh in cytop and anch to PM at intercell junc-desmosome. CA lot keratin somew unus=epith ori. skin blist by mut keratin gene.
• mt- long hollow cyling. tubulin monom. where strucs are moved eg nerve fib, mitot spind, cilia, flag. 25nm. ori from centrosome-tubulin add/subtr. 9+2 arr in cilium/flag. v cons. 2mt mid, 9 doublets periph. 13 alpha and beta tubulin su polym= wall of hollow mt. att prots eg dynein and kinesin can att organelles and move strucs along mt’s eg chroms spind.