Oxidative Phosphorylation

Question 1

Where does ox pho occur?

Answer 1

In the inner membrane of the mitochondria; bc the outer membrane in porous and the inner is impermeable

Question 2

Reduced cofactors role in the electron transfer chain

Answer 2

NADH, NADPH, FADH; Electron carriers that donate their electrons to the electron transport chain on the matrix side

Question 3

Where do the reduced Cofactors need to go?

Answer 3

From the cytosol (intermembrane space to the matrix)

Question 4

Malate-Apartate shuttle system in matrix

Answer 4

Malate is converted to oxaloacetate by malate dehydrogenase and NAD+ —-> NADH + H+ to produce one additional NADH in the matrix

Question 5

Malate-Asp shuttle system in the cytosol

Answer 5

Oxaloacetate is converted to malate by by malate dehydrogenase and NADH + H+ —> NAD+; produces one fewer NADH in the cytosol

Question 6

What is the reason behind NADH having a higher concentration in the matrix than cytosol

Answer 6

NADH is too large to be efficiently transported into the matrix

Question 7

How do you move oxaloacetate back to the cytosol

Answer 7

By converting it to aspartate so it can be transported as Asp to be reconverted to Oxaloacetate

Question 8

Where is ATP produced

Answer 8

In the matrix

Question 9

How are ADP and ATP moved across the inner membrane?

Answer 9

Using an antiporter driven by inner membrane potential; the matrix contains ATP (4 negative charges) and the cytosol contains ADP (3 negative charges) that allow flow of ATP to be exported into the cytosol

Question 10

How is Pi imported into the matrix?

Answer 10

Via a symport driven by H+ gradient where there is lower H+ in the matrix

Question 11

Complex 1 NADH dehydrogenase

Answer 11

4 H+ are translocated into the cytosol for every 2 e- that pass through the complex

Question 12

Electron path in NADH dehydrogenase

Answer 12

2 e- are released as NADH is oxidized; those e- are transferred to FMN; FMNH2 then passes the e- (one at a time) to a series of iron clusters until they reach Q to form Q2

Question 13

What is NADH characterized as

Answer 13

A water soluble mobile 2 e- carrier

Question 14

Flavins

Answer 14

Prosthetic group that can carry 1 or 2 e-

Question 15

Fe-S Clusters

Answer 15

Cysteines and inorganic sulfur carry 1 e- from FADH2 to Q

Question 16

Ubiquinone is characterized as

Answer 16

A lipid soluble, mobile 1 or 2 e- carrier

Question 17

Where else can the cell get QH2

Answer 17

1. Sussinate dehydrogenase complex to produce FADH2
2. From fatty acid oxidation from the acyl-CoA dehydrogenase rxn
3. From Glycerol-3-Phosphate from the mitochondrial dehydrogenase reaction

Question 18

Complex 3 Cytochrome bc1

Answer 18

Ubiquinol (QH2) donates 2 e- to complex 3, reducing cytochrome c; 4 H+ are transloacted into the cytosol for every 2 e- that pass through the complex

Question 19

Cytochrome C

Answer 19

Mobile single electron carrier

Question 20

Cytochrome C

Answer 20

Mobile single electron carrier

Question 21

Complex 4: Cytochrome c oxidase

Answer 21

Cytochrome C proteins each donate 1 electron to complex 4, reducing the terminal electron acceptor O2.
2 H+ are transloaced into the cytosol for every 2 e- that pass through complex 4

Question 22

Cytochrome structure

Answer 22

Cytochromes are Proteins with heme group that are single electron carriers and 3 side groups on the heme

Question 23

Complex 1 reduction potential

Answer 23

-69.6

Question 24

Complex 3 reduction potential

Answer 24

-36.7 kj/mol

Question 25

Complex 4 reduction potential

Answer 25

-112 kj/mol

Question 26

What is oxidative phosphorylation regulated by

Answer 26

The availability of NADH and QH2

Question 27

Chemiosmotic Model

Answer 27

Combination of the H+ imbalance (due to e- transport) and the negative charges on the matrix side of the membrane results in an electrochemical gradient that factors H+ moving into the matrix

Question 28

F1

Answer 28

Soluble portion holding 3 alpha and 3 beta subunits each with synthase activity

Question 29

F0

Answer 29

Membrane spanning portion that includes a subunit where H+ enters and exits and a C ring

Question 30

C ring

Answer 30

Consists of 8-15 subunits that each bind an H+ to help rotate the ring

Question 31

Complex V (F1F0ATP Synthase)

Answer 31

H+ gradient is used to generate ATP where H+ move down their gradient by passing through ATP synthase; 1 ATP produced for every 4 H+ (no matter how many subunits are in the c-ring)

Question 32

Y subunit of complex V

Answer 32

Extends from F0 to F1 and rotates 120 degrees once enough strain has built up from the c ring rotation;

Question 33

Beta L confirmation

Answer 33

Loose; ADP+ Pi are bound

Question 34

Beta T conformation

Answer 34

Tight; ATP is formed

Question 35

Beta O conformation

Answer 35

Open; ATP is released

Question 36

What does one full rotation of the y subunit yield?

Answer 36

3 ATP (1 per each beta subunit)

Question 37

P:O ratio

Answer 37

Ratio of phosphorylations (ADP + Pi —> ATP) to oxygen atoms reduced (1/2 O2 + 2 H+ + 2 e- —>h20)

Question 38

How many H+ does NADH translocate?

Answer 38

Complex 1: 4 H+ Complex 3: 4 H+ Complex 4: 2 H+ Total = 10

Question 39

How many ATPs does NADH generate

Answer 39

10 H+ x (1 ATP/ 4H+)= 2.5 ATP (PO ratio)

Question 40

How many H+ does QH2 oxidation translocate?

Answer 40

Complex 3: 4 H+ Complex 4: 2 H+ Total = 6

Question 41

How many ATP does QH2 generate

Answer 41

6 H+ x (1 ATP/4H+)= 1.5 ATP (PO ratio)

Question 42

What does oxygen consumption indicate

Answer 42

That electrons are moving through the electron transport chain

Question 43

How does CN- target oxidative phosphorylation?

Answer 43

It blocks e- transport through complex IV therefore shutting down the entire e- transport chain and preventing the formation of the H+ gradient

Question 44

Role of Ventruicidin and oligomycin

Answer 44

They block the H+ channel in ATP synthase which causes the ETC to slow down as the H+ gradient gets too steep (doesn’t stop completely some H+ still leak)

Question 45

Role of succinate

Answer 45

May be added to mitochondria to generate QH2

Question 46

What does O2 consumption indicate?

Answer 46

Electron transport is working

Question 47

What does ATP synthesis imply?

Answer 47

That protons are moving through ATP synthase

Question 48

Uncoupling protons

Answer 48

Can uncouple oxidative phosphorylation and provide a path to bring H+ down their concentration gradient without passing through ATP synthase; free energy in this process generates heat and can denature proteins

Question 49

How many translocated protons does it take to make 1 ATP

Answer 49

4 H+ make 1 ATP