Organelle Ecology - mitochondria

Question 1

how connected do mitochondria seem to be, based on microscopic evidence?

Answer 1

not really, very little recovery between mitochondria in FRAP imaging

Question 2

how does mitochondial division change across organisms

Answer 2

algal etc mitochondria- internal and external ring, presumably the primitive state as similar to bacterial division

yeast/animal mitochondria have ER constriction around the cell, and some internal constriction machinery (not a ring)

Question 3

yeast mitochondria division mechanism

Answer 3

external dynamin ring, tethered to the membrane by Fis1
fission ultimately triggered by GTP hydrolysis

Question 4

ERMD

Answer 4

ER-associated mitochondrial division

ER, mitochondria, and actin are bridged- constriction and division

Question 5

mechanism of mitochondrial fusion

Answer 5

mitofusin GTPases, known as Mfn1/2, act as linkage proteins and allow connection of the membranes

Opa1 causes ‘pore opening’, and allows a larger, single mitochondrion which shares cristae are formed

Question 6

importance of fusion and fission in controlling cell stress and damage

Answer 6

can either segregate or dilute mitochondrial damage, without needing to necessarily destroy the entire organelle

fusion can also be prevented if damage has led to a loss of membrane potential

Question 7

how do cells ensure all mitochondria have the same DNA?

Answer 7

mtDNA occurs in multi-copy nucleoids which are kinda everywhere along the mitochondrial network
mitochondria have different levels of DNA- heteroplasmy

heteroplasmy can be reduced slightly, and mixing ensured, by fission

Question 8

benefit of mitochondrial ‘networks’ over individual mitochondria

Answer 8

energy conducting ‘routes’- allows more efficient movement of energy, and means cells can be bigger basically

Question 9

why might mitochondria be a prerequisite for complexity, rather than vice versa?

Answer 9

genomes of mitochondria-containing cells have higher ‘power per gene’, despite slower respiration rate, as the mitochondria can lose a lot of genes and rely on the cell for safety/metabolites/etc

Question 10

note to self i am skipping all the maths stuff because i dont like it. but yeah its also here.

Answer 10

okay <3