Bio 28 ETC & OXPHOS

Question 1

Where are the protons concentrated in the mitochondria?

Answer 1

Intermembrane space

Question 2

Which membrane is permeable and which is not in the mitochondria?

Answer 2

Outer membrane is very permeable, inner is very much not.

Question 3

How many NADH and FADH2 are made per turn of the TCA cycle?

Answer 3

3 NADH plus 1 from PDHC

1 FADH2

Question 4

How many ATP are made from 1 NADH or 1 FADH2?

Answer 4

1 NADH->3 ATP

1 FADH2->2 ATP

Question 5

How are NADH and FADH2 produced during the fasting state?

Answer 5

During fasting, most cells switch over to Beta Oxidation of fatty acids which produces these molecules for the ETC.

Question 6

Describe the flow of electrons in the ETC.

Answer 6

NADH-> complex I
FADH2-> complex II
Ubiquinone transports form I & II to complex III
Cytochrome C transports from III to IV where they are transported to O2 to become water

Question 7

What transfers e- from complexes I & II to III, and what accepts the e- at III?

Answer 7

Ubiquinone or coenzyme Q

Cytochrome B is in III

Question 8

What transfers e- from complex III to IV and what accepts the e- in IV?

Answer 8

Cytochrome C

Cytochrome a&a3 are in IV

Question 9

What is the final e- accepter in the ETC?

Answer 9

Oxygen

Question 10

Which complexes transport protons?

Answer 10

I, III, IV

II does not because it does not span the membrane

Question 11

How do pyruvate, inorganic phosphate, ADP, and ATP cross the IMM?

Answer 11

The proton gradient is used to power the transport of these molecules across the membrane. All but ATP go into the matrix.
ADP/ATP transports well because the net charge on ATP is more negative than on ADP so the positive charge from the protons in the IMS pulls the neg ATP out.

Question 12

How is the ETC regulated?

Answer 12

Primarily through energy level. ATP allosterically inhibits complex IV.
Also by substrate concentration.

Question 13

What is the protein that makes the ATP in the mitochondria through oxidative phosphorylation?

Answer 13

Complex V or ATP synthase

Question 14

What are the two ETC inhibitors mentioned and how do they work?

Answer 14

Cyanide: binds to the iron (Fe3+) in complex IV and stops the transfer of e-

Carbon Monoxide: binds Fe2+ in complex IV and in hemoglobin (mostly in Hb though)

All decrease substrate utilization and decrease energy production.

Question 15

What is uncoupling?

Answer 15

ETC runs without producing any ATP. This happens because protons are allowed to leak back into the matrix without going through ATP Synthase.
Causes heat generation, use of substrates, no energy production.

Question 16

Give an example of a protein and chemical uncoupler.

Answer 16

Uncoupling Proteins: in brown fat cells, create channels for proton transport, found in babies and hibernating animals

2,4 dinitrophenol (DNP): transports a proton across the IMM

Question 17

What is the danger with DNP?

Answer 17

Causes the ETC to run and produce a lot of heat. Death can occur from hyperthermia.

Question 18

What happens to ETC, TCA, Glycolysis in fed state when energy levels are good?

Answer 18

ATP builds up in mitochondria, inhibiting further production of energy.
NADH/FADH2 build up in cytosol and slow TCA cycle.
Citrate builds up in mitochondria and overflows to cytosol which helps fatty acid synthesis and inhibits glycolysis.