Power Conversion in Mitochondria I

Question 1

What can flavins accept as part of a reduction process?

Answer 1

2H+ and 2e-

Question 2

What prosthetic groups do cytochromes contain?

Answer 2

heme

Question 3

What redox chemistry can hemes do?

Answer 3

Electron reduction going from Fe³⁺ to Fe²⁺

Question 4

What does the midpoint potential of hemes depend on?

Answer 4

the structure of heme and the local environment of proteins

Question 5

What kind of Fe do Fe-S centres contain?

Answer 5

Non-heme iron

Question 6

What redox chemistry do Fe-S centres do?

Answer 6

Electron reduction from Fe³⁺→Fe²⁺

Question 7

What role can Copper have in redox proteins?

Answer 7

• Can be single Cu
• Can be in a 2Cu cluster with S atoms

Question 8

What redox chemistry can ubiquinone do?

Answer 8

• Reduced in 2 sequential steps of electron transfer
• The 2nd step also allows 2H⁺ to be taken up

Question 9

What is the maximum distance redox centres can be apart to allow for electron transfer?

Answer 9

15Å

Question 10

what happens to electron transfer when redox centres are bound to protein?

Answer 10

They are capable of much faster electron transfer

Question 11

Which amino acids can accept or donate a H+ to become charged?

Answer 11

Glu, Arg, Asp, His, Lys

Question 12

What do pKa values of amino acids depend on?

Answer 12

Local enviornment and conformational changes to protein

Question 13

How can H+ move in ETC?

Answer 13

Can move from one amino acid to another along charged residues as electron move down electron wire, the energy is conserved and used to pump H+ against conc gradient

Question 14

How many core subunits does mitochondrial complex I contain?

Answer 14

46

Question 15

What are the 2 types of domains in mitochondrial complex I?

Answer 15

• Hydrophobic peripheral domain
• Membrane domain

Question 16

What is complex I also called?

Answer 16

NADH dehydrogenase

Question 18

What happens in the hydrophobic domain of complex I?

Answer 18

• NADH oxidised to NAD+ and H+
• 2 electrons passed onto FMN, then passed to 7 Fe-S centres
• Finally 2 electrons passed to Q forming QH₂

Question 19

What does the hydrophobic domain of complex I contain?

Answer 19

Redox cofactors

Question 20

Does the membrane domain of complex 1 contain redox centres?

Answer 20

No

Question 21

What happens in membrane domain of complex 1 ?

Answer 21

Pumps H+ across membrane of matrix into intermembrane space

Question 22

In membrane domain of complex 1 how many H+ are pumped per 2 electrons?

Answer 22

4

Question 23

What is the structure of membrane domain of complex 1?

Answer 23

• 3 conserved membrane subunits which are homologous to H+/Na+ antiporters
• Proton wire through centre of complex

Question 24

What likley forms H+ channel in membrane domain of complex 1?

Answer 24

Conserved essential polar and charged residues

Question 25

What kind of mechanism is used for proton pumping in complex 1?

Answer 25

Indirect mechanism

Question 26

How does proton pumping occur in complex I?

Answer 26

• electron movement produces energy, dirivng conformational changes
• these cause a shift in pKa of an amino acid and changes in structure to give outward facing conformation
• electrons passed down again resets protein