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MBOD Week 10 > Mitochondria and Oxygen Metabolism > Flashcards

Mitochondria and Oxygen Metabolism Flashcards

1
Q

How many total mitochondrial genes are there, and how many of these are encoded for by mDNA?

A

683 genes in mitochondria

13 genes come from mitochondrial genome

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2
Q

How do most (98%) of proteins enter the mitochondria?

A

Import machinery

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3
Q

what bacteria do mitochondria show a strong relationship to and why is this so?

A
  • alpha proteobacteria

- mitochondria were acquired through endosymbiotic event

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4
Q

T or F: the outer membrane of the mitochondria is fairly permeable.

A

True, it is porous to small molecules up to 5000 Da

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5
Q

T or F: the inner membrane is permeable to ions.

A

False, very impermeable to ions, especially protons

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6
Q

Where does cytochrome c reside?

A

in the intermembrane space

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7
Q

What important structures are held in the inner mitochondrial membrane?

A
  • Electron transfer complexes
  • ATP synthase
  • Carrier proteins to exchange metabolites between cytosol and matrix
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8
Q

Describe the structure of cristae.

A

Tubes and flattened sacs with limited connections to the portion of the inner membrane that lines the outer membrane

  • Small openings to the inner membrane space may limit diffusion of metabolites like ADP and ATP
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9
Q

T or F: the state of the cristae changes in response to physiological conditions.

A

True, in times of high energy consumption/ATP production they fuse to allow for easier diffusion of particles

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10
Q

What is the difference in state 3 and 4 respiration.

A

State 3 - active state of respiration, lots of ADP and O2 being used up

State 4 - Resting state respiratoin, little ADP and very little O2 being used up

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11
Q

What happens to the cristae in active state 3 and why?

A
  • There is is fusion of the cristae

- Fusion may open bottlenecks to diffusion and allow rapid exchange of metabolites with the cytosol

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12
Q

What protein has been linked to cristae morphology and why?

A
  • mitofillin
  • part of MINOS (mitochondrial inner membrane organizing system)

**These play a critical role in dynamic changes that take place in the mitochondrial structure during respiration

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13
Q

What happens when the gene coding for mitofillin is knocked out?

A

mitochondrial inner membranes appear like layers of an onion but they are not connected to each other or to inner boundary membrane

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14
Q

Explain how mitochondria are important in apoptosis.

A
  1. Bad, Bax, or Bid binds to mitochondrial receptor and causes the membrane to become leaky
  2. Cytochrome C leaks to the cytosol
  3. Cytochrome C unites with Apaf-1
  4. Cyto C + Apaf-1 recruit caspase 9

Note: caspases are cystein proteases that must be activated

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15
Q

T or F: the outer membrane of the mitochondria is similar to the outer membrane of the cell.

A

True

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16
Q

T or F: the protein to lipid ratio is about 1:1 by weight on the outer mitochondrial membrane

A

True

17
Q

Can BID cause changes in the shape of the cell cristae?

A
  • It has been indicated that it does

- Mouse liver treated with trucated BID showed a dramatic effect on the cristae

18
Q

What allows the outer membrane to be porous to small molecules?

A

Porin Channel proteins

19
Q

T or F: the inner membrane has a higher protein to lipid ratio than the outer membrane.

A

True, its 3:1

20
Q

What phospholipid is unique to the inner membrane and what does it do?

A
  • Cardiolipin - unique to the inner membrane

- Its associated with many of the membrane complexes and is required for optimal function

21
Q

What disease results from a defective cardiolipin biosynthesis gene?

A
  • Barth symdrome

- Results in defective mitochondria causing cardiomyopathy and muscle weakness

22
Q

How does the inner membrane get things like ADP and pyruvate from one side of the membrane to the other?

A
  • Antiporters
23
Q

What does ADP/ATP antiport depend on?

A
  • membrane potential

- charges on the substrates

24
Q

Why do diseases of mitochondrial origin often result in the production of reactive oxygen species?

A
  • mitochondrial enzymes work to reduce oxygen to water
  • If one of these enzymes functions incorrectly then one of the reduced intermediates of oxygen can be released causing damage to the cell
25
Q

What enzyme exists in the mitochondria to eliminate superoxide (ROS), what disease results from a defect in this enzyme?

A
  • superoxide dismutase

- Lou Gehrig’s disease (cytosolic form)

26
Q

What enzyme reduces H2O2 to water and O2?

A

Catalase (found in mitochondria and also in blood cells)

27
Q

Name two free radical scavengers that protect against the hydroxyl radical (ROS).

A

Vitamin C and E

28
Q

What would you expect to happen if the proton gradient in the mitochondrial membrane were to be uncoupled?

A
  • This proton gradient would dissipate
  • ATP would not be made to work in feedback inhibition
  • Heat would be generated
29
Q

How does heme get into RBCs?

A
  • Made in the mitochondria of RBCs before they loose all of their organelles
30
Q

How do ribosomes and proteins enter the mitochondria?

A
  • Mitochondria must import proteins (NOT THROUGH CARRIERS)

- doesn’t need to import RNAs because they are encoded for in the ribosome

31
Q

Where are porins located?

A

The outer membrane

32
Q

Where is cardiolipin located?

A

inner membrane

33
Q

Where is mitofilin found?

A
  • inner boundary membrane
34
Q

Where are mitochondrial carriers located?

A

On the inner membrane

35
Q

What is the job of MINOS and what lipid is MINOS dependent on?

A
  • MINOS binds cardiolipin
  • acts like a diffusion barrier
  • this ensures the protein composition of the inner boundary membrane is different from the cristae membranes
36
Q

Which membrane becomes leaky as a result of Bad, Bit, or Bax binding that allows cytochrome c to escape?

A

Outer membrane

MBOD Week 10 (5 decks)

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