26 - OxPhos Regulation

Question 1

A successful OxPhos must accomplish what key goals?

Answer 1

1) Transfer electrons from NADH and FADH2 — O2
2) Establish a proton gradient across the inner mitochondrial membrane
3) To synthesize ATP

Question 2

Electrons flow from the molecules with (LOWER/HIGHER) Eo (standard redox potential – energy) to that with the (LOWEST/HIGHEST) Eo. The difference in Delta Eo is associated with Delta G, which are inversely related.

Answer 2

Lower

Highest

Question 3

Electron transfer through the respiratory chain lead to the pumping of _____ from matrix to the inner-mitochondrial space.

Answer 3

H+

Question 4

Two factors constitutes a proton-motive force (pmf) to drive ATP synthesis by complex V. These factors are…

Answer 4

1) pH gradient

2) Membrane potential

Question 5

Who proposed the chemiosmotic hypothesis (1961/1978), making it a revolutionary idea at the time?

Answer 5

Peter Mitchell

Question 6

The chemiosmotic theory consist of 3 postulates. Postulate 1 – The mitochondrial electron-transport chain translocates ________ across the inner mitochondrial membrane as electron flows from one respiratory electron-transport chain complex to the next.

Answer 6

Protons

Question 7

The chemiosmotic theory consist of 3 postulates. Postulate 2 – ATP synthase uses the proton motive force (pmf) to drive the phosphorylation of ______.

Answer 7

ADP

Question 8

The chemiosmotic theory consist of 3 postulates. Postulate 3 – The inner mitochondrial membrane is _________ to H+ and OH- ions. If the membrane is disrupted, a pmf cannot be established, and ATP synthesis does not occur.

Answer 8

Impermeable

Question 9

ATP synthase is called complex _____ and is embedded in the inner membrane of the _________.

Answer 9

V

Mitochondria

Question 10

ATP synthase has a ball and stick structure. The _____ subunit is the stick and is embedded in the membrane and has a proton channel. The _____ subunit is the ball, and protrudes into the matrix side, it contains catalytic domains.

Answer 10

F0

F1

Question 11

The F1 subunit of ATP synthase is composed of what?

Answer 11

alpha-3
beta-3
gamma
delta
epsilon

Question 12

In the F1 subunit of ATP synthase, how are the alpha and beta subunits arranged?

Answer 12

Alternately in a hexameric ring

Question 13

In the F1 subunit, both alpha and beta subunits can bind nucleotides but only _______ are catalytically active.

Answer 13

beta

Question 14

In the F1 subunit, above the alpha and beta is a stalk made of what proteins?

Answer 14

gamma

epsilon

Question 15

In the F1 subunit, the _______ subunit has a long helical coil that extends into the center of the alpha-3 and beta-3 hexamer.

Answer 15

gamma

Question 16

ATP synthase molecules associate with each other to form ________, which come together to form ________.

Answer 16

Dimers

Oligomers

Question 17

ATP synthase oligomers stabilize the individual molecules to ________ forces required for catalysis, and maintains curvature in the inner membrane.

Answer 17

Rotational

Question 18

________ allow the proton gradient to be in close proximity to the ATP synthase.

Answer 18

Cristae

Question 19

This is an inhibitor that disrupts proton transport through the channel in ATP synthase.

Answer 19

Oligomycin

Question 20

Making and exporting one ATP costs about _____ hydrogens (protons).

Answer 20

4

Question 21

ATP and ADP are not permeable across the mitochondrial membrane, they need a carrier which is called…

Answer 21

ATP-ADP translocase

Question 22

ATP-ADP translocase reside in the outer and inner mitochondrial membranes and works with mitochondrial carriers. It was recently assigned as complex _____.

Answer 22

VI

Question 23

The flow of ATP and ADP is ________, this means ADP enters the matrix only if ATP leaves the matrix.

Answer 23

Coupled

Question 24

Reduced NADH cannot cross the mitochondrial membrane, so two shuttle systems are used which are…

Answer 24

1) Malate-aspartate shuttle

2) Glycerophosphate shuttle

Question 25

This shuttle operates in the heart, liver, and kidneys. It generates reduced NADH in the mito-matrix. From this, reduced NADH enters to the ETC at Complex-I.

Answer 25

Malate-aspartate shuttle

Question 26

This shuttle operates in the skeletal muscle and brain. It generates reduced FADH2 in the inner mito-membrane. Reduced FADH2 joins to ETC at CoQ.

Answer 26

Glycerophosphate shuttle

Question 27

Levels of _____ regulate respiration. Electrons flow through ETC only when _____ is phosphorylated to _____.

Answer 27

ATP
ADP
ATP

Question 28

Regulation by ADP levels called ________ control or _______ control.

Answer 28

Respiratory

Acceptor

Question 29

When the transfer of electrons is inhibited in OxPhos, what happens?

Answer 29

1) Decrease in the pumping protons
2) Decrease in the protein gradient
3) Inhibition of ATP synthesis

Question 30

Some organisms can uncouple OxPhos from ATP synthesis. Instead, it is used to generate ______ and maintain ______ ______ (hibernating animals).

Answer 30

Heat

Body temperature

Question 31

Uncoupling of OxPhos happens in this tissue, which is rich in mitochondria and get its color due to cytochrome and hemoglobin.

Answer 31

Brown adipose tissue

Question 32

The inner mitochondrial membrane contains uncoupling protein _____, also called ________.

Answer 32

UCP 1

Thermogenin

Question 33

UCP 1 transfers protons from the cytoplasm to the matrix side and energy is converted to _______ instead of ATP.

Answer 33

Heat

Question 34

UCP 2 and UCP 3 also uncouple OxPhos from ATP synthesis. They play a role in…

Answer 34

Energy homeostasis

Question 35

UCP (proton leak) in the production of heat is important for the thermogenesis in what tissue?

Answer 35

Brown adipose tissue