ETC & Ox Phos

Question 1

Only ~35% of the E released from the oxidation of NADH is captured by the synthesis of 2.5 ATP molecules. The rest of the free E is released as

Answer 1

heat

Question 2

Summary of ETC & OxPhos:

Answer 2

1. ETC: Electrons are stripped from NADH or FADH₂ and passed along the electron transport chain until transferred to O₂ –> H₂O
   
   1. ​Meanwhile, H+ are pumped across the IM out of the matrix into the cytosol
2. Ox Phos: H+ ions are allowed back into the matrix via ATP synthase
   
   1. The potential E of dissipating this ion gradient is captured to power the synthase –> ATP produced from ADP

Question 3

Cytochromes types A, B, and C each have different ___.

Cytochrome electron carriers have ____ in their center, which is important because___

Answer 3

Each have different protoporphyrin ring structures

All have iron (Fe) which goes between the 2+ (reduced) and 3+ (oxidized) states to carry electrons

Question 4

Iron-sulfur proteins

Answer 4

Fe is coordinated to the protein through cystein sulfur-containing side groups. Fe cycles between the +2 (reduced) and +3 (oxidized) states

Question 5

Ubiquinone (coenzyme Q) carries ___ electrons, so it has 3 redox states: __, ___, and __.

Answer 5

carries 2 electrons

Ubiquinone (Q)

Semiquinone (QH)

Ubiquinol (QH₂)

Question 6

What is the order of the protein complexes of the ETC?

Answer 6

I - NADH dehdyrogenase

II - succinate dehydrogenase

III - ubiquinone cytochrome c oxidoreductase

IV - cytochrome oxidase

Question 7

What happens at complex I

Answer 7

NADH dehydrogenase turns NADH to NAD+

4 H+ pumped out of matrix

Question 8

Complex II of ETC

Answer 8

Succinate dehydrogenase- entry point for FADH₂

FADH₂ it produces from CAC is transferred into the ETC through iron/sulfur proteins

No H+ pumped

Question 9

Complex III of ETC

Answer 9

Ubiquinone/CoQ is a lipid-linked carrier that receives e- from Complex I or II and transfers it to…

Complex III, which contains heme and iron/sulfur protein e- carriers.

4H+ are pumped out of the matrix

Question 10

After complex III, electrons are transferred to ___ and then to ___, which has heme & copper to transfer these electrons to O2 to create H2o.

In the process, __ additional H+ ions are pumped out of the matrix

Answer 10

Complex III > Cyt C > Cytochrome oxidase > O2

2 additional H+ are pumped out of the matrix

Question 11

Distingusih electron flow from NADH and FADH2

Answer 11

NADH skips Complex II : Complex I > CoQ …..

FADH2 skips Complex I : Complex II > CoQ…

Question 12

Different electron sources that enter Co enzyme Q

Answer 12

NADH dehydrogenase (Complex I)

Succinate dehydrogenase (Complex II)

IMM G3P dehydrogenase (Glycerol-phosphate shuttle)

Acyl-CoA Dehydrogenase (FA-oxidation)

Question 14

Electrons from NADH in complex I provide enough E to pump a total of _ H+ out of the matrix

Electrons from FADH₂ in complex II provide enough E to pump a total of __H+ out of the matrix.

Generating a negative matrix and a positive intermembrane space.

Answer 14

NADH .. 10 H+

FADH₂ .. 6 H+

Question 15

Describe the ATP synthase complex

Answer 15

• F₀ is embedded in the membrane; its C₁₀ ring forms a pore in the membrane that lets H+ enter the matrix.
  
  • As H+ enters, they cause the ring to rotate in the lipid bilayer (electrochemical E is converted to mechanical E)
• F₁ spins when the ring does, causing the B subunit to bind ADP Pi and then synthesize ATP when it strikes the F₀ gamma subunit.

Question 16

It takes ~ __ H+ to spin the F1 subunit sufficiently to generate ox phos of ADP to ATP

Answer 16

4 H+

Question 17

Rotenone

Answer 17

broad-spectrum pesticide/insecticide that inhibits electron transfer between Complex I and CoQ

Everything downstream stays oxidized - no oxphos.

Question 18

Antimycin A

Answer 18

Fish poison

blocks cytochrome C oxidoreductase

Question 19

Cyanide or CO inhibit

Answer 19

cytochrome oxidase in complex IV

Question 20

Poisons that inhibit either the ETC or ATP synthase caues

Answer 20

heart attack because without ATP, the heart doesn’t pump and the lungs don’t fxn

Question 21

Aurovertin, Oligomycin, Venturicidin, and DCCD inhibit..

Answer 21

ATP synthase

Question 22

Chemical uncouplers

Answer 22

Allows H+ to re-enter the matrix without ATP synthase

The E is released as heat instead of proton motive force (can cause hyperthermia)

Question 23

DNP

Answer 23

An uncoupler.

In the acidic cytosol, it binds a proton that makes it neutral –> can penetrate IMM to enter matrix –> loses its proton, dissipating the proton gradient

Question 24

FCCP

Answer 24

similar to dNP

Question 25

Where does uncoupling occur naturally?

Answer 25

Brown fat in your shoulders and back have a bunch of cytochrome-containing mitochondria and expresses a natural uncoupler, thermogenin to generate heat.

Question 26

Regulation of oxidative phosphorylation

Answer 26

• Stimulated by ADP
• Inhibited by ATP (& lowkey lactic and pyruvic acid)
• Requires oxygen

Question 27

Ions and other polar molecules are transported across the inner membrane by

Answer 27

specific protein translocases that nearly balance charge during the transport process

Question 28

How do ATP and ADP enter the inner mitochondrial membrane?Co

Answer 28

ATP-ADP antiporter (type of cotransporter)

Maintains charge across the membrane

Question 29

Transporters that dissipate the overall positive H+ ion charge and the proton motive force:

Answer 29

• Pyruvate & H+ symporter into the matrix
• HPO₄^2- & H+ symporter into the matrix
• Ca²⁺ enters the matrix

THIS IS ANOTHER REASON WHY ATP FROM ETC AND OXPHOS IS LESSENED (2.5 and 1.5 instead of 3 and 2)

Question 30

Total net ATP yield from complete oxidation of glucose is

Answer 30

30 or 32, depending on the shuttle system used

Question 31

All o the electron transfer reactions in the ETC result in the translocation of protons from the matrix to the inner membrane space EXCEPT the one catalyzed by

Answer 31

Complex II

Question 32

What do we mean when we say that the processes of electorn transport and ATP synthesis are coupled?

Answer 32

If ATP synthesis does not occur, the H+ gradient becomes so steep that H+ cannot be translocated

Question 33

CO binds specifically to cytochrome a in Complex IV and disrupts its ability to transfer electorns. IF high conc of carbon monoxide are added to actively respiring mitochondria,

• CoQ will become more oxidized, while cytochrome c will become more reduced
• CoQ will become more reduced, while cytochrome c will become more oxidized
• both CoQ and cytochrome c will become more reduced
• both will become oxidized

Answer 33

• both CoQ and cytochrome c will become more reduced

Question 34

What will be the consequences of adding an uncoupler to actively respiring mitochondria?

Answer 34

Rate of electorn ransport will increase, but the extent of proton gradient and the rate of ATP synthesis will both decrease