Mitochondria

Question 1

4 compartments

Answer 1

• outer membrane
• inner membrane
• intermembrane space
• matrix

Question 2

outer membrane

Answer 2

-permeable to molecules up to 10 kDa

Question 3

inner membrane

Answer 3

• impermeable
• molecules need a specific transporter/shuttle to pass through
• oxidative phosph proteins are located here

Question 4

matrix

Answer 4

-contains TCA cycle enzymes and mitochondrial DNA

Question 5

mtDNA

• size
• copies
• encodes

Answer 5

• different from genomic DNA
• small, circular (17kb)
• up to 10,000 copies per cell
• encodes 13 oxphos proteins, 2rRNAs and 22tRNAs

Question 6

majority of mitochondrial proteins are…

Answer 6

• encoded for in genomic DNA
• synthesized in the cytosol
• have to be transported into the mitochondria

Question 7

mitochondrial import of proteins is carried out by

Answer 7

• TOM (outer membrane)

- TIM (inner membrane)

Question 8

targetting region of mitochondrial proteins

Answer 8

-typically N-terminal

Question 9

energy requirement of proteins getting into the mitochondria

Answer 9

• energy dependent process

- proteins must be unfolded upon entry and refolded once inside

Question 10

TOM proteins

Answer 10

transport proteins from the cytoplasm through the outer membrane

• TOM70: transports proteins that are destined to be integral membrane proteins in the inner membrane of the mitochondria
• TOM20: transports proteins that are destined to reside in the matrix
• TOM40: this is the actual channel protein which the mitochdria bound proteins pass through (lives in the outer membrane)

Question 11

TIM proteins

Answer 11

-responsible for getting mitochondrial proteins through the inner membrane

Question 12

Step 1 of oxidative phos

Answer 12

• called the respiratory chain

- a series of redox couples that transfer electrons from donors (NADH, succinate) to the final acceptor, oxygen

Question 13

step 2

Answer 13

• transfer of protons from the matrix into the intermembrane space, creating a membrane potential between matrix and intermem space.
• this is called a proton gradient
• this is done via energy created from the respiratory chain

Question 14

what complexes push electrons into intermembrane space

Answer 14

1,3,4

Question 15

step 3

Question 16

F0 complex

Answer 16

• part of complex 5 of oxphos

- proton channel in the mitochondrial inner membrane

Question 17

F1 complex

Answer 17

-contains 3 ATP synthesizing active centers (faces mitochondrial matrix)

Question 18

mechanics of F0F1 ATP synthesis

Answer 18

• F0 lets in protons creating a mechanical force that produces a confirmational change in active centers on F1
• these confirmational changes promote ATP synthesis

Question 19

oligomycin

Answer 19

-inhibitor of ATP synthase

Question 20

coupling

Answer 20

• interdependence of the rates of the respiratory chain (e transfer/oxygen consumption) and the rate of ATP synthesis
• this means that if one is inhibitted, it will directly inhibit the other

Question 21

two main factors in the rate of ATP synthesis

Answer 21

• availibility of substrates of complexes 1 and 2 (NADH and succinate) (uncommon)
• availability of ADP for ATP synthase (very frequent)

Question 22

uncoupling

Answer 22

• loss of coupling between respiratory chain and ATP synthase
• happens if protons are allowed back into the matrix without going through ATP synthase (through a different proton channel)
• membrane potential is abolished, respiratory chain is working at full steam, and ATP synthase isnt generating any ATP
• this will produce heat instead of ATP

Question 23

how to test coupling

Answer 23

treat cells/mitochondria with oligomycin and measure oxygen consumption
-if it is decreased then mitochondria is coupled

Question 24

uncouplers

Answer 24

• FCCP, dinitrophenols, UCP1/thermogenin

- brown fat contains mitochondria and burns calories at maximal rates

Question 25

uncoupled mitochondria and obesity

Answer 25

• uncoupling forces respiratory chain to burn calories at a maximal rate without doing work
• this could be useful against obesity, however, heat production could be a harmful side affect

Question 26

ANT

Answer 26

• adenine nucleotide translocase
• transports newly synthesized ATP from the mitochondrial matrix into the cytosol and ADP from cytosol into the mitochondrial matrix

Question 27

inhibitors of ANT

Answer 27

• altractyloside

- bongkrekic acid

Question 28

mitochondrial permeability transition

Answer 28

• loss of the impermeability of inner mitochondrial membrane
• caused by the permanent opening of the ANT pore caused by eg excess of calcium
• triggered through calcium dependent binding of matrix protein cyclophilin D to ANT
• can be inhibited by a non-specific CypD inhibitor (cyclosporine A)
• MPT happens in the cardia and neuronal cells during times of ischemia
• MPT causes collapse of the mitochondrial membrane potential (stopping ATP synthesis), destruction of the mitochondrial outer membrane and release of pro-apoptotic molecule from the intermembrane space