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MCB 2050 > Mitochondria and Chloroplasts - Chloroplasts > Flashcards

Mitochondria and Chloroplasts - Chloroplasts Flashcards

1
Q

what are chloroplasts

A

semi-autonomous plant cell organelle

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2
Q

what are chloroplasts involved in

A

photosynthesis
fatty acid and amino acid biosynthesis
nitrogen and sulfur assimilation

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3
Q

how are chloroplasts often highly mobile

A

they move along cytoskeleton elements via molecular motors

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4
Q

what kind of organelle is a chloroplast

A

double membrane bound

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5
Q

what does the chloroplast envelope consist of

A

outer and inner membranes

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6
Q

what does the outermembrane contain

A

porins that are not as permeable to ions/small molecules as mitochondria

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7
Q

qualities of inner membrane

A

highly impermeable, contains various transports

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8
Q

what are thylakoids

A

3rd membrane system

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9
Q

thylakoid morphology

A

flattened membranous discs arranges in stacks or between stacks

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10
Q

grana thylakoid

A

thylakoid in stack

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11
Q

stromal thylakoid

A

thylakoid between stacks

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12
Q

what are thylakoid membranes

A

site of ATP synthase
maintain H+ gradient in thylakoid lumen

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13
Q

thylakoid lumen

A

aqueous interior of thylakoid with high [H+]

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14
Q

what is the stroma

A

aqueous interior - space inside envelope and outside of thylakoids

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15
Q

what does the storm contain

A

enzymes involved in carb synthesis and plastid genome

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16
Q

what is the plastid genome in stroma

A

circular
encodes ribosomal proteins, some Ps proteins
ribosomes

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17
Q

how are chloroplasts often connected

A

via stromules

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18
Q

what are stromules

A

long, stroma-filled membrane tubules
branched and dynamic

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19
Q

what do stromules allow for

A

efficient metabolite transfer and communication

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20
Q

what do stromules do rapidly

A

extend and contract

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21
Q

how do chloroplasts multiply

A

fission

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22
Q

what is chloroplast fission

A

divide in synch in response to environmental stimuli and/or developmental signals

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23
Q

example of developmental signals that get a response by fission

A

at the end of G1 - organelle duplication prior to S phase

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24
Q

what are the 2 sets of protein machineries involved in chloroplast division

A

FtsZ and PD

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25
what do FtsZ and PD both form
ring-like structures either on inside or outside of chloroplast envelope
26
what do the rings formed by FtsZ and PD do
tighten and pinch organelle into 2 daughter chloroplasts
27
what kind of machinery does FtsZ have
internal machinery on stroll side of inner membrane
28
what does FtsZ include
FtsZ1 and FtsZ2
29
what are FtsZ1 and FtsZ2
soluble stromal proteins homologs of bacterial division protein FtsZ
30
what do FtsZ1/2 spontaneously assemble into
long, filamentous polymers at midway point (equator) on inner membrane surface
31
what do FtsZ1/2 form
FtsZ-ring at future chloroplast division site
32
what is the initial positioning of the FtsZ proteins at equator mediated by
soluble stromal proteins: ARC3 MinD MinE
33
what is mediated by ARC6
linkage of Z-ring to inner membrane at chloroplast division site
34
what is the integral inner membrane-spanning protein localized to in dividing chloroplast
the equator
35
what does the stromal-facing domain of ARC6 do
links to and stabilizes FtsZ-ring
36
what can disrupt the fission process
mutation in ARC6 gene - results in formation of 1-2 giant chloroplasts
37
what does ARC6 control
tightening of FtsZ-ring
38
what does ARC6's interaction with Z-ring signal the start of
chloroplast constriction process
39
what does the IMS-facing domain of ARC6 bind to
Plastic Dividing (PD) machinery in chloroplast outer membrane
40
what does PD machinery include
PDV1 and PDV2
41
what are PDV1 and PDV2
hetero-dimeric, integral outer transmembrane proteins recruited to midway point in dividing chloroplast via ARC6
42
what do PDV1 and PDV2 also bing to
ARC5
43
what is ARC5
cytoplasmic, soluble dynamin-related GTPase protein
44
what does ARC5 assemble into
spiral-like structures to from PD-ring
45
what does the PD-ring do
wraps around outside of chloroplast - tightening via GTP-hydrolysis causes constriction of outer envelope
46
what work together for division
FtsZ and PD machineries
47
how do the 2 daughter chloroplasts get formed
through concerted action of both internal Z-ring and external PD ring
48
what do all chloroplast proteins possess
unique targeting sequences
49
what do the specific sequences of amino acids serve as
zipcodes
50
what do the amino acid zip codes mediate
protein targeting from cytoplasm to chloroplast surface protein targeting from cytoplasm to specific sub chloroplast compartment
51
what do most stromal-destined proteins possess
stromal import sequence
52
where is the stromal import sequence located
proteins N-terminus
53
what is the stromal import sequence enriched in
hydroxylated residues and small hydrophobic resides
54
does a amphipathic alpha-helix get formed by stromal import sequence
no
55
when does the stromal import sequence get cleaved
following protein import into stroma
56
what is the stromal import sequence responsible for
targeting nascent stromal protein to cytoplasmic surface of chloroplast subsequent translocation across out and inner membranes
57
what is the Toc complex
multi protein complex that includes receptor subunits, transmembrane channel and various accessory proteins
58
why is GTP involved in binding stromal import sequence to Toc receptor
there is energy requirement for import
59
when are Toc and Tic complexes adjacent to each other
contact sites
60
how does precursor protein translocation occur across both membranes
sequentially - unlike mitochondria NOT mediated by [H+] electrochemical potential
61
how does Hsp93 act as a molecule motor
undergoes ATP dependent conformational changes that pulls protein into storm and prevent backsliding
62
what does Hsp93 assist with
protein folding
63
what doe molecular chaperone proteins in stroma ensure (Hsp93)
cleaved, mature protein properly folded
64
what are TOC and TIC complexes also involved in
import or insertion of other chloroplast proteins
65
how do all nuclear-encoded chloroplast proteins access chloroplast
through Toc and/or Tic complexes
66
what does folded protein import in pH dependent pathway reply on
energy from proton (change in pH) gradient between stroma and lumen
67
which [H+] is larger in pH-dependent pathway
[H+] thylakoid lumen is larger than [H+] stroma

MCB 2050 (11 decks)

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