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CDB > Mitochondria and Chloroplast > Flashcards

Mitochondria and Chloroplast Flashcards

1
Q

What are the mitochondrial protein complexes?

A
  • NADH dehydrogenase (Complex I;NDH)
  • succinate dehydrogenase (Complex II)
  • bc1 or cytochrome complex (Complex III)
  • cytochrome oxidase (Complex IV; COX)
  • ATP synthase
  • cytochrome c
  • lipid soluble ubiquinone
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2
Q

What topologies can mt genomes take?

A
  • circular
  • linear
  • maxicircles
  • minicircles
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3
Q

How does yeast mt splicing occur?

A
  • Type I splicing requires GTP and Mg and creates circular intron
  • Type II requires a hairpin and Mg and produces a lariat
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4
Q

How does animal mt transcription work?

A
  • Similar RNA polymerase to yeast but transcription intitated at one site
  • Translation stop codon not encoded but added via polyadenylation
  • The mt likely use altered codons which differ between species
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5
Q

How to higher plants use RNA editing to alter codon usage?

A
  • predominantly modify C to U

- Typansomes make more extensive use of RNA editing

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6
Q

What’s different with mt mRNA transcription?

A
  • Don’t have all tRNA genes, import from nucleus
  • Make use of wobble to recognise some codons
  • Sensitive to antibiotics
  • No evidence for mRNA import
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7
Q

What are plastids

A
  • Chloroplasts are plastids and are interconvertible. Originate from protoplastid
  • Chromoplasts, in flowers and fruits, red, yellow orange
  • Leucoplats, in mature plant cells(roots) drive synthesis of fatty acids, amino acids and cofactors
  • Amyloplasts in roots, seeds, storage, contain starch
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8
Q

What are the structures in chloroplast membranes?

A
  • Photosystem II, oxygen evolving complex
  • b6f cytochrome complex
  • Photosystem I
  • ATP synthase
  • plastocyanin (PC)
  • ferredoxin (Fd)
  • ferredoxin-NADP reductase (FNR)
  • ## Plastoquinone, lipid soluable
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9
Q

Do mt and chloroplast genomes vary in size?

A
  • mt vary significantly

- chloroplast not as much

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10
Q

What evidence indicates strong homology between chloroplast and Ecoli genomes?

A
  • Chloroplast genes can be expressed in ecoli
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11
Q

What polymerases does chloroplast have?

A
  • plastid encoded polymerase (PEP), similar to ecoli

- nucleaur encoded polymerase (NEP), similar to bacteriophage/mt

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12
Q

.

A

.

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13
Q

Do most genes in mt and chloroplast originate from nucleus or organelle?

A
  • Nucleus due to limited coding capacity
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14
Q

What ribosomes translate mt and cp proteins?

A
  • Free ribosomes
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15
Q

What signals do mt/cp directed proteins have?

A
  • presequence or transit peptide which guide it through membrane transport
  • no signal seq as they don’t arise in ER
  • no sequence similarity between species but tend to have; rich hydroxyl amino acids, positive charge, few acidic
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16
Q

Is the presequence necessary and sufficient for mt/cp protein import?

A
  • Yes, mature proteins not imported
17
Q

What are the TOM complexes made of?

A
  • tom20, receptor for presequence
  • tom22 organizer of TOM
  • tom40 outer membrane channel
  • tom70 receptor for hydrophobic carriers, transfers to Mitochondrial Import Complex( MIM)
  • MIM inserts alpha helical proteins into outer membrane
18
Q

What are the TIM complexes made of?

A
  • tim15 receptor for presequence
  • tim21 connects tim to tom
  • tim23 channel for precursor protein from TOM,
  • tim22 inserts proteins into inner membrane, carrier translocase
  • OXA inserts mt or imported proteins into membrane
19
Q

What is the mt inter membrane space?

A
  • Contains chaperons
  • Eukaryote specific
  • Mitochondrial intermembrane assembly (MIA) helps for disulphide bridges, no homolog
20
Q

How are nuclear proteins processed in mt matrix?

A
  • Mitochondrial Processing Peptide cleaves presequence
  • Hsp60 helps fold in mt
  • Hsp70 attached to tim23 as a heat shock protein which helps pull protein across membrane
21
Q

What is the SAM complex in mt import?

A
  • inserts beta barrel proteins into outer membrane
22
Q

How does plastid to cp biogenisis occur in higher plants(not genes)?

A
  • Chloroplasts genisis requires light, absence forms etioplast plastids
  • Regulation posttranslational, so transcripts present in dark
23
Q

How do chloroplast transcripts regulate nucleus transcription (retrograde signalling)?

A
  • tagetoxin and lincomycin nd chloramphenicol prevent nuclear expression of early seedling development
  • An example is etioplast exposure to light releasing haem and phytochromoilin which upregulate LHC gene in nucleus which causes chloroplast transiiton
24
Q

How can nuclear mt incompatibilities affect resistance to disease?

A
  • different peoples will have different resistances to different diseases and conditions

CDB (13 decks)

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