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Molecular Cell Biology > Lecture #2 > Flashcards

Lecture #2 Flashcards

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AP® Biology flashcards
1
Q

what is mitochondrial DNA transcribed as?

A

a polycistronic unit

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2
Q

what do miRNAs act as?

A

post-transcriptional regulators and translational repressors

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3
Q

describe the expression of miRNAs

A

tissue-specific

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4
Q

describe the overall roles of miRNA:

A

both pathological and physiological

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5
Q

what are miRNAs coded from and processed by?

A

coded from nuclear DNA and processed by DNA polymerase II

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6
Q

what shape is pre-miRNA characterized by?

A

a hairpin loop

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7
Q

besides the cytosol, where is it proposed that miRNAs can also be found?

A

in mitochondria

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8
Q

what are the 6 potential ways that miRNAs can enter into the mitochondria?

A

through a specific motif at the 3’ terminal, through post-transcriptional modifications, with the help of PNPase, with the help of AGO2, through import inside of P bodies when in complex with AGO2, or by PUMILIO1 and AGO2 working in tandem

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9
Q

what was found to be associated with micromiRNAs when isolated from WT mouse cerebellum?

A

an interaction between mitomiRNA and AGO2

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10
Q

what cells have been shown to rely the most on mitochondria?

A

in neural cells

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11
Q

what are the three levels of mitochondrial quality control?

A

molecular, organelles, and cellular

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12
Q

what is a mirnome?

A

a library of all miRNAs present inside mitochondria of cerebella

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13
Q

what cells rely the most on mitochondria?

A

neurons

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14
Q

what two things are linked to transport across neurons?

A

both energy production and ion balance

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15
Q

what does ion balance directly control in neurons?

A

movement

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16
Q

what two areas of the body do mitochondrial dysfunctions affect?

A

neurons and muscles

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17
Q

what is mitophagy?

A

the fusion and fission events together with transport coupled with degredation of mitochondria

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18
Q

if mitophagy fails to recover damage, what occurs?

A

apoptosis is triggered via the release of cytochrome C

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19
Q

when apoptosis is triggered, where is the cytochrome C released from?

A

released from the inner membrane space to the cytosol

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20
Q

list the three ways in which the control of the mitochondrial proteome is not exerted in an autonomous way:

A

or proteins located on the outer mm, proteins containing disulphide bonds, and translocons that are engulfed and cannot import proteins from the outside

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21
Q

what is the degredation of proteins located on the omm called that is an exception from the typical autonomous degredation referred to as?

A

mitochondrial associated degradation

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22
Q

what is mitochondrial associated degredation of proteins located on the omm reminiscent of?

A

ER associated degredation (ERAD)

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23
Q

what is unique about each sub-compartment inside of mitochondria?

A

there is a specific quality control system for each compartment

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24
Q

what do proteases in the matrix always have?

A

presequences that travel by TOM40 -> TIM23 motor pathway, then cleaved and folded by Hsp60

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25
Q

if proteins brought into the matrix are folded improperly, what two proteases are involved in degredation?,

A

LON protease (LONP) and CLPXP protease

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26
Q

what is LONP?

A

a highly conserved serine-protease that degrades unfolded, damaged, or oxidized proteins

27
Q

due to the leakage of electrons from the respiratory chain, what are abundant in the mitochondria?

A

reactive oxygen species (ROS)

28
Q

what is the function of PTRM1 peptidase?

A

digests dipeptides into aa that are then transported outside to be recycled

29
Q

what are the two specific proteases located in the inner mitochondrial membrane?

A

m-triple A and i-triple A

30
Q

describe m-triple A and its position:

A

a hexameric complex arranged in which the catalytic chamber is directed towards the matrix space

31
Q

describe the i-triple A protease:

A

hexameric complex in which the proteolytic chamber is directed towards the intermembrane space

32
Q

m-triple A and i-triple A are integral to the membrane as well as their target proteins, so how can they decide what to degrade?

A

the presence of a hydrophobic domain outside the membrane

33
Q

what specifically are recognized by m-triple A and i-triple A on proteins tagged for degredation?

A

solvent exposed domains - if there is a mutation that alters the folding of the state of these proteins

34
Q

how do AAA proteases handle proteins that need to be degraded?

A

they exert a retrograde translocation of the protein - cut it and insert it in the proteolytic chamber for degredation

35
Q

what does AAA stand for?

A

ATPase Associated with different cellular Activities

36
Q

Describe the two roles of AAAs?

A

act like chaperones and proteases together - they can sense the protein folding state but can also degrade proteins

37
Q

when are subunits of AAAs generally mutated?

A

in neuron degenerative diseases

38
Q

what are the two key proteases of the intermembrane space?

A

HTRA2 and ATP23

39
Q

what is the function of HTRA2?

A

highly conserved and forms a trimeric complex - important for the degredation of oxidized proteins

40
Q

what is ATP23?

A

a metalloprotease

41
Q

what is organellar quality control based on?

A

mitochondrial dynamics

42
Q

what is molecular quality control based on?

A

control of proteostasis

43
Q

what are the three different states of mitochondrial network?

A

tubular, intermediate, and fragmented

44
Q

describe the tubular mitochondrial network:

A

mitochondria are elongated and highly interconnected

45
Q

describe an intermediate mitochondrial network:

A

mitochondria are still tubular however the tubulars are shorter and not as connected

46
Q

describe a fragmented mitochondrial network:

A

there isnt a network anymore and there are many individual structures

47
Q

In order to be healthy, what must mitochondria balance?

A

fusion and fission events - cells need to shift their mitochondrial network depending on cellular needs

48
Q

what is most often the cause of disease when mitochondria are involved?

A

excessive fusion or fission events

49
Q

primary defects in fusion and fission events are related to what diseases in children?

A

neurological diseases of early childhood

50
Q

in terms of generation, what makes mitochondria different than other organelles?

A

they are not generated de novo

51
Q

what happens in autophagy?

A

autophagosome engults organelles that are not functioning properly and by fusing with lysosomes, degrades them

52
Q

what is the final aim of autophagy?

A

to recycyle organelles and proteins

53
Q

what is the triggering event for mitophagy?

A

depolarization

54
Q

deploarization triggers a pathway in which what specifically happens?

A

specific proteins are exposed on the omm in order to recruit the the machinery for autophagy degredation

55
Q

before autophagy is triggered, what do mitochonria try to use instead?

A

the salvage pathway such as fusion / fission events or the reverse activity of the ATPsintase in order to prevent depolarization

56
Q

besides depolarization, what is another prerequisite for mitophagy?

A

fragmentation - autophagosome cannot englulf an entire network

57
Q

how does the reversal of ATPsynthase work to promote degredation of miotchondria?

A

ATPsynthase is able to comsume ATP in order to pump the protons back into the intermembrane space in order to re-establish the mitochondrial membrane potential

58
Q

what is the fastest way to assess the mitochondrial membrane potential?

A

TMRM

59
Q

what happens if ATPsynthase is blocked in healthy cells?

A

the amount of protons in the ims are increased and there is a high polarization

60
Q

what happens if ATPsynthase is blocked in unhealthy mitochondria?

A

the mitochondrial membrane potential goes down

61
Q

what are the two main players in fision and fussion events?

A

MFN1 and MFN2

62
Q

what mediates the fusion of the omm?

A

MFN1 and MFN2

63
Q

what complex mediates the fusion of the imm?

A

OPA1 (optic atrohpy 1)

64
Q

what disease is MFN2 mutated in?

A

Charcot-Marie-Tooth disease (peripheral neuropathy)

Molecular Cell Biology (10 decks)

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