Oxidative Phosphorylation

Question 1

what makes proton gradient so powerful?

Answer 1

concentration and voltage gradient both in same direction

Question 2

what is ATP synths?

Answer 2

synthesizes ATP from ADP and Pi

Question 3

what are the two portions of the ATP Synthase?

Answer 3

Membrane portion (Fo)

matrix portion (F1)

Question 4

what does the membrane portion do?

Answer 4

translocates H+

Question 5

what does the matrix portion do?

Answer 5

synthesizes ATP

Question 6

what is the effect of proton binding to Fo?

Answer 6

drives rotation of the “c” subunits, which makes γ rotate, which stimulates conformational changes in the F1 β subunits, making ATP.

Question 7

where is the F1 head piece located? what about the F0 pore?

Answer 7

matrix, composed of 6 subunits, alternating alpha and beta subunits, 1 pair is an alpha and beta so a total of three catalytic sites;
inner mitochondrial membrane

Question 8

what causes the conformational change of the ATP synthase?

Answer 8

the movement of protons into the FO portion of the ATP synthase, it causes a turret like motion which is connected by a stalk like portion or a gamma/epsilon subunit

Question 9

what are the sites located in the F1 head group? Does the headgroup move? how does the binding change mechanism work?

Answer 9

Three sites: one is empty, one contains ADP + Pi,
one contains ATP

no

energy favorable for the making of ATP, energy is needed to remove the ATP from its active site and this happens due to the turning of the gamma subunit while also forming ATP from ADP and Pi, empty site becomes loaded

Question 10

what is proton motive force due to?

Answer 10

membrane potential and proton concentration gradient

Question 11

What is the purpose of setting up the H+ gradient?

Answer 11

its set up by the proton gradient that drives ATP synthesis by ATP synthase phosphorylating ADP to ATP

Question 12

what is needed to ensure the proper functioning of the ETC?

Answer 12

1) all the components of ETC to create the proton gradient
2) ATP synthase to synthesize ATP
3) Oxygen – terminal acceptor of e- so that electrons can move through ETC
4) Reducing coenzymes (NADH and FADH2) to provide electrons
5) intact inner mitochondrial membrane for the H+ gradient.

Question 13

ATP synthesis is dependent on?which requires ____ as an electron source?

Answer 13

ETC; NADH/FADH2

Question 14

what does the formation of the proton gradient promote?

Answer 14

ATP synthesis

Question 15

during ATP synthesis, this requires O2 reduction to H2O T/F?

Answer 15

True

Question 16

why is proton transport through the ATP synthase important?

Answer 16

ATP synthesis is dependent on this

Question 17

in ATP synthesis, what happens to ADP?

Answer 17

its phosphorylated to ATP

Question 18

what are the effects when ATP synthesis controls the rate of ETC O2 consumption?

Answer 18

it decreases supply of NADH/FADH2

stimulates ETC to regenerate the H+ gradient

increases the rate of O2 consumption

depletes the inter membrane space of H+

ADP conversion to ATP

Question 19

where does NADH come from?

Answer 19

TCA, Glycolysis, Fatty acid oxidation

Question 20

what is ATP-ADP translocase?

Answer 20

Ensures steady supply of ADP for ATP synthase. Flow down their concentration gradients

Requires energy equivalent of one H+

H+ gradient drives Pi into matrix for synthase: 1 to 1 ratio

Question 21

the outer membrane is a voltage or chemical gradient?

Answer 21

voltage gradient

Question 22

why does ATP synthesis require an intact inner mitochondrial membrane with an H+ gradient?

Answer 22

The ETC makes the proton gradient. The ATP Synthase uses the gradient’s energy.
The ATP Synthase is the major pathway for H+ reentry into the matrix.

Any agent that allows H+ to pass into the matrix will “uncouple” the ETC (which generates H+ gradient) from ATP synthesis (which uses the H+ gradient) so ETC will continue but ATP production is affected and this is called uncoupling

Question 23

what is the effect of a minor H+ leak versus a major H+ leak?

Answer 23

Only a little H+ leak? Proton gradient sufficient to drive ATP, just slower.

Major H+ leak? Proton gradient not sufficient to support ATP synthesis at needed level.

Question 24

what is brown fat?

Answer 24

helps keep the body warm like babies and used to generate heat for baby

Question 25

how does brown fat work to generate heat?

Answer 25

signal detected from environment and this stimulates release of norepinephrine, this stimulates beta adrenegic receptor, G-protein, adenylate cyclase, cAMP/PKA which activates hormone sensitive lipase which releases free fatty acids from triglyceride which enter the mitochondrial matrix for oxidation leading to rise in ATP activating Thermogenin

Question 26

what is thermogenin?

Answer 26

this is also called uncoupled protein 1 and this is activated by the free fats and so the proton pore opens (based on need) and so protons are brought back to matrix which stimulates ETC but no ATP, but produces heat…free fats are oxidized in matrix, UCP1 loses activation, closes pore, H+ gradient re-established, normal ATP. If this is not coupled to ETC, it is dissipated as heat and so cell warms up becoming a warming mechanism

Question 27

what is an example of a harmful chemical uncoupler discussed in class? describe function and effects?

Answer 27

Dinitrophenol (DNP) was thought to be an ideal drug for weight loss.

Protonated DNP will “carry” a proton across the inner mitochondrial membrane, release it in the membrane where the pH is higher (less protons), this collapses the proton gradient

Thought process: uncoupler will decrease H+ gradient. ETC will be activated, which will consume more NADH and FADH2. This in turn will activate catabolic pathways – esp. Fatty Acid Oxidation. Goal – shrink adipose tissue over time.

Blindness, metabolic failure, death

Question 28

what are mitochondrial myopathies?

Answer 28

Deficiency in Oxidative Phosphorylation: TCA Cycle, ETC, ATP Synthase and most of the proteins are encoded by nuclear DNA and some named by Mitochondrial DNA

Question 29

what causes mitochondrial myopathies?

Answer 29

Protein synthesis or targeting errors of nuclear encoded proteins cause loss of function

Mitochondrial DNA errors or damage can cause loss of function (e.g., free radical damage)

Question 30

what are the effects of mitochondrial dysfunction?

Answer 30

TCA cycle deficiency (affects number of electrons through ETC), anoxia, ischemia, CO poisoning of the ET chain preventing electron flow and ATP synthesis and also genetic defects

Question 31

A patient is exposed to a toxin molecule that destroys the function of cytochrome c. Apart from cytochrome c, which Electron Transport Chain components will be oxidized and which will be reduced? (Answer oxidized or reduced)

Complex I
Complex II
Coenzyme Q
Complex IV

Answer 31

A-C reduced, then D is oxidized

Question 32

A patient is exposed to a toxin molecule that destroys the function of cytochrome c. How will the proton gradient across the inner mitochondrial membrane change over time?

A. No effect: the membrane is still intact
B. The proton gradient will increase continuously.
C. The proton gradient will decrease over time.
D. The ETC will be activated to try to restore the proton gradient.

Answer 32

C. The proton gradient will decrease over time.

Question 33

A patient is exposed to a toxin molecule that destroys the function of cytochrome c. How will this affect ATP synthesis by oxidative phosphorylation?

A. No effect: cytochrome c is part of the ETC, not Ox Phos
B. ATP synthesis will be inhibited.
C. ATP synthesis will be activated.
D. Glycolysis will be the main source of ATP generation.

Answer 33

B. ATP synthesis will be inhibited.

Question 34

A patient is exposed to a toxin molecule that destroys the function of cytochrome c. How will this affect glycolysis?

A. No effect: glycolysis is in the cytoplasm not the mito matrix.
B. Glycolysis will be activated initially, but inhibited in the longer term.
C. Glycolysis will no longer produce NADH to avoid inhibition.
D. Glycolysis will become an aerobic ATP generation pathway.

Answer 34

B. Glycolysis will be activated initially, but inhibited in the longer term.

Question 35

A patient is exposed to a mitochondrial uncoupler. How will this affect the function of her glycolysis pathway?

A. No effect: glycolysis occurs in the mitochondrial matrix.
B. Glycolysis will be inhibited.
C. Glycolysis will be activated.
D. Glycolysis will be dependent on cellular O2

Answer 35

C. Glycolysis will be activated.