Oxidative Phosphorylation and Respiratory control

Question 1

ATP is created in oxidative phosphorylation by:

Answer 1

movement of protons back into the mitochondrial matrix through complex V (also called the ATP synthase).

Question 2

Two essential functions of electron transport:

Answer 2

1. Pump protons out of mitochondrial matrix

2. Reoxidize NADH and FADH2 to NAD and FAD, respectively

Question 3

3 Components of Chemiosmotic hypothesis by Peter Mitchell that shows how mitochondria make ATP in oxidative phosphorylation:

Answer 3

a. Intact inner mitochondrial membrane
b. Electron transport creates a proton gradient
c. ATP is made by movement of protons back into the mitochondria

Question 4

Coupling of electron transport and oxidative phosphorylation at a practical level means that the mitochondrial inner membrane remains impermeable to ____. Except for those that enter via the ____.

Answer 4

• Protons

- ATP synthase

Question 5

The ATP synthase consists of a turbine-like structure containing 3 sites called:
Also talk about their function

Answer 5

• Loose (L): Holds ADP and Pi in preparation for ATP formation
• Tight (T): Causes ADP and Pi to join and form ATP
• Open (O) :Releases ATP formed in T and binds ADP + Pi

Question 6

What causes rotation/conformational changes from (L to T to O to L) of ATP synthase that results in ATP formation.

Answer 6

Movement of protons

Question 7

If you poke a hole in the mitochondrial membrane (using DNP or an uncoupling protein, such as found in brown fat) what happens?

Answer 7

Protons can leak back in without making ATP. Generate heat AND burn up energy sources (like glucose and fat).

Question 8

What is DNP?

Answer 8

DNP is a dangerous compound that killed people who tried to use it to lose weight by making holes in mitochondrial matrix. Caused NAD to increase, stimulated citric acid cycle, burned sugars/fats to make ATP since wasn’t making them from protons.

Question 9

When mitochondria are tightly coupled, metabolic/ respiratory control exists. What would happen is oxidative phosphorylation stopped?

Answer 9

Electron transport will stop if oxidative phosphorylation stops, since the protons don’t come back in and the proton gradient gets very high, stopping the pumping of protons. When electron transport stops, NADH accumulates and the citric acid stops.

Question 10

What happens if one stops electron transport with cyanide?

Answer 10

oxidative phosphorylation will stop very shortly because the proton gradient is lost when no protons are being pumped.

Question 11

This molecule cannot cross the inner membrane of the mitochondrion, as there is no protein to move it:

Answer 11

NADH

Question 12

____ make it into the mitochondria by means of shuttles.

Answer 12

Electrons

Question 13

Insect muscles contain this shuttle that transfers electrons from NADH to FAD in complex II, making FADH2

Answer 13

glycerol-3phosphate/DHAP

Question 14

Mammalian systems use what system to convert oxaloacetate to malate (carrier of electrons) that then get transported by a transport protein?

Answer 14

a malate aspartate system

Question 15

Once inside the matrix (via a transport protein) malate tranfers electrons to what? What does this create?

Answer 15

Transfers electrons to NAD+ which creates NADH.

Question 16

What complex is ADP critical for?

Answer 16

Complex V (ATP synthase)

Question 17

How does ADP make its way to the mitochondrion?

Answer 17

Via the ATP/ADP translocase, which is an antiport moving ATP out of the mitochondrion as ADP is moved in.

Question 18

Photosynthetic fish by using Bacteriorhodophsin (which moves between cis/trans and uses Vit A to pump protons out):

Answer 18

If bacteriorhodopsin is put on a transparent fish, and light is shone onto it, then the bacteriorhodopsin would pump protons to help the proton gradient allowing it to make ATP from light instead of food.

Question 19

Brown fat contains a protein called Uncoupling Protein that can do what?

Answer 19

insert itself into the mitochondrial inner membrane and allow protons to flow into the matrix, bypassing complex V

Question 20

Why does the uncoupling protein do this?

Answer 20

To generate heat. This may be important in keeping cells of the central nervous system warm.