Oxidative Phosphorylation

Question 1

Describe permeability of outer mitochondrial membrane.

Answer 1

Permeable to small molecules and small proteins.

Question 2

Describe permeability of inner membrane.

Answer 2

Impermeable to small and large molecules

Question 3

Where does oxidative phosphorylation occur?

Answer 3

Inner mitochondrial membrane

Question 4

Explain how you can have an electrochemical gradient with no membrane potential.

Answer 4

Negative membrane potential inside, positive membrane potential outside.

Question 5

What is the fastest way and preferred way for NADH to shuttle H+?

Answer 5

Take it straight to complex I of ETC from cytosol to mitochondrial matrix

Question 6

What is a slower, irreversible way for NADH to shuttle H+ to ETC?

Answer 6

NADH transfers H+ to glycerol 3-phosphate which then moves into the inner mitochondrial matrix where FAD takes the H+ and moves it to CoQ of the ETC.

Question 7

Describe the function of the first complex in ETC and its name.

Answer 7

NADH Dehydrogenase complex

Transfer electron from NADH to chain of iron-sulfur clusters. Reduces ubiquinone to ubiquinol. Then Ubiquinone or CoQ transfers protons to next complex.

Question 8

Describe function of third complex in ETC.

Answer 8

Cytochrome b-c1 complex - CoQ recycling and transfer of electrons to cytochrome C

Question 9

Describe function of fourth complex in ETC.

Answer 9

Cytochrome oxidase

• 4 electrons enter one at a time from cytochrome c
• Cu, protein side chains, Fe atom on cytochrome oxidase collect all the electrons
• O2 binds to the active site and is reduced
• 4 protons are pumped out of matrix back into intermembrane space

Question 10

How many H+ ions does it take to make 1 ATP?

Answer 10

About 3

Question 11

Describe protein transport conformations of cytochrome oxidase.

Answer 11

Conformation A - high affinity for H+, proton uptake
Conformation B - H+ binds to cytochrome oxidase
Conformation C - low affinity for H+, proton released to outside of cell

Question 12

What is the total aerobic energy yield from one molecule of glucose? Break down where the ATPs come from.

Answer 12

32 ATP total

Glycolysis (2 NADH, 2 ATP)
PDH complex (2 NADH)
TCA (6 NADH, 2 FADH2, 2 GTP)

Question 13

What is the total anaerobic energy yield from one molecule of glucose?

Answer 13

2 ATP total

Question 14

What binding-specificity does electron transport rely on for stability and energy efficiency?

Answer 14

Binding-specificity of mobile carriers with complexes I-IV

Question 15

Where is ubiquinone a free carrier?

Answer 15

Lipids

Question 16

Where is cytochrome C a free carrier?

Answer 16

intermembrane space

Question 17

How will a low NAD:NADH ratio affect respiration?

Answer 17

It will slow it b/c there is no reducing agent available

Question 18

How will a steep proton gradient affect respiration?

Answer 18

It will slow it b/c it will slow electron transfer

Question 19

How will a high ADP level affect respiration?

Answer 19

It will increase it

Question 20

What is an NADH dehydrogenase inhibitor of ETC?

Answer 20

Amytal rotenone

Question 21

What is a cytochrome b-c1 complex inhibitor of ETC?

Answer 21

Antimycin A

Question 22

What are some cytochrome c oxidase inhibitors of ETC?

Answer 22

CN, CO, azide

Question 23

What is an F1FoATPase inhibitor?

Answer 23

Oligomycin

Question 24

What is an ATP/ADP exchange inhibitor?

Answer 24

Atractyloside bongkrektate

Question 25

What are some uncouplers of respiration? How do they work?

Answer 25

FCCP, DNP (they collapse the H+ gradient) They collapse the proton gradient and thus allow protons to re-enter the mitochondrial matrix without energy being captured as ATP—the energy is released as heat and the process is called non-shivering thermogenesis. This prevents the synthesis of ATP but will normally increase respiration and electron transport.

Question 26

What is a reactive oxygen species and how does it form?

Answer 26

Electron transfer in the mitochondria occasionally allows oxygen to escape before it is fully reduced to water. Escape as a superoxide anion radical (-O2) can lead to the formation of H2O2 or the hydroxyl radical (ROS) which can induce DNA and protein damage.

Question 27

What do superoxide dismutase and glutathione peroxidase do?

Answer 27

Converts superoxide anion radical into intermediary H2O2 before glutathione peroxidase adds an H, making a water molecule.

Question 28

How are mitochondrial myopathies obtained?

Answer 28

They are maternally inherited defects in genes encoding mitochondrial tRNAs. Mitochondrial DNA mutates at a much faster rate than nuclear DNA, increasing chance of mitochondrial myopathies.

Question 29

How do mitochondrial myopathies present?

Answer 29

Muscle weakness and/or neurological symptoms

Question 30

What are the two categories for mitochondrial myopathies?

Answer 30

MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes) MERRF (myoclonic epilepsy and ragged red fibers)