Lecture 22

Question 1

what does the electron transport do

Answer 1

makes a proton gradient across the inner membrane

Question 2

what does the mitochondria convert reduction potentials too

Answer 2

proton gradient then into ATP

Question 3

protons per complex 1, 3,4

Answer 3

1- 4
Q-4
4-2

Question 4

what does electron microscopy suggest about the complexes

Answer 4

they are “supercomplexes” referred to as a respirasome

Question 5

what is coupled with the proton gradient

Answer 5

ATP synthesis

Question 6

E- cant flow if the pH gradient is what

Answer 6

too steep

Question 7

what to chemical uncouplers do?

Answer 7

dissipate the proton gradient
ex: 2,4 DNP
FCCP
CCCP

Question 8

DNP (dinitrophenol)

Answer 8

• Powerful “slimming” drug
• >100,000 people treated in 1930’s
• Converts fat directly into heat.
• Very narrow therapeutic window.
• Slight overdose causes catstrophic loss of energy in the body.
– Excessive sweating, extreme thirst, cataracts, irreversible damage to heart, liver, lungs.
– Ultimately paralysis, death.
• First drug to be banned by FDA – 1938.

Question 9

what inhibits the ATP synthase

Answer 9

oligomycin and venturicidin

Question 10

How much ATP is made?

Answer 10

• Every NADH that enters complex I yields about 2.5 ATP
• Every FADH2 that enters complex II yields about 1.5 ATP

These numbers can change depending on how UNCOUPLEDthe mitochondria are.

Question 11

Mitochondrial uncoupling

Answer 11

• Brown Fat generates heat
– Hibernating animals.
– Newborn infants.
– Lots of mitochondria in fat tissue makes it brown.

Question 12

How is the energy in the proton gradient

captured to make ATP?

Answer 12

**AT.P Synthase **

Question 13

Like an electric motor, ATP synthase.

Answer 13

stationary parts and rotating parts

Question 14

γ-subunit

Answer 14

coiled-coil inserts into the central cavity of the α3β3 complex γ-subunit coiled-coil is asymmetric

Question 15

Stator + αβ-subunits

Answer 15

do not rotate

Question 16

what drives the rxn

Answer 16

Protonation and Re-ionization of a
glutamate in c-ring subunits

• The c-ring rotates next to the a-subunit
• The a-subunit & c-ring provide a path for H+ to
cross the membrane
• 2 half-channels in the a-subunit & glu residues in c-ring subunits

Question 17

what drives the conformational changes

Answer 17

Rotation of the γ-subunit drives Conforma@onal Changes in the αβ subunits Interconvert between Tight, Loose, and Open conformations

Question 18

how many atps does one full rotation of y subunit produce?

Answer 18

3

The β-subunits are the catalytic subunits.
Substrate binding sites are at the α/β subunit interface
The γ-subunit rotates, the αβ-subunits do not.

Question 19

ATP Synthase: The movie

Answer 19

As it rotates, the asymmetry of γ-subunit coiled-coil
drives sequential conformational changes in the α3β3 complex between Tight, Loose, and Open conforma@ons, synthesizing ATP from ADP and Pi

The γ-subunit is tightly coupled to the c-ring. A path for protons across the membrane is provided by channels in the a-subunit and the protona@on and reionization of glutamate residues in the c-ring subunits.

Question 20

The ATP synthase is BIG, it dimerizes and helps fold?

Answer 20

cristae

Question 21

How much ATP is made

Answer 21

• How many protons pumped per NADH?
• 10 protons
• How many protons per ATP synthase cycle?
• 8 protons / 3 ATP = ~2.7 protons / ATP
• for 10 protons (1 NADH) expect even more ATP

• Co-transport systems that move ADP & Pi into the mitochondrial matrix and ATP out use some of the energy stored in the proton gradient

Question 22

experimental atp produced

Answer 22

Every NADH that enters complex I yields about 2.5 ATP

Every FADH2 that enters complex II yields about 1.5 ATP

Question 23

Glucose to lactate yields ATP

Glucose to CO2 yields ATP

Answer 23

2 ATP

32 ATP

Question 24

Pyruvate to Acetyl CoA
(per mole pyruvate)

ATP, NADH, FADH2?

Answer 24

ATP= 0
NADH= 1
FADH2= 0

Question 25

citric acid cycle (per mole pyruvate)

ATP, NADH, FADH2?

Answer 25

ATP= 1
NADH= 3
FADH2= 1

Question 26

Total/mole pyruvate

ATP, NADH, FADH2?

Answer 26

ATP= 1
NADH= 4
FADH2= 1

Question 27

Total/mole glucose mitochondria

ATP, NADH, FADH2?

Answer 27

ATP= 2
NADH= 8
FADH2= 2

Question 28

Glycolysis (per mole glucose) cytoplasm

ATP, NADH, FADH2?

Answer 28

ATP= 2
NADH= 2
FADH2= 0

Question 29

ATP, NADH, FADH2?

Answer 29

ATP= 0
NADH= 1
FADH2= 0

Question 30

Overall total/mole glucose

Answer 30

ATP= 4
NADH= 10
FADH2= 2

Question 31

Key concepts for Oxidative Phosphorylation

Answer 31

• Respiratory chain pumps protons across the inner mitochondrial membrane.
• Uncouplers and inhibitors of ATP synthase can influence oxygen consumption.
• ATP synthase functions as a rotary motor with three active sites and a ring that moves as it binds and releases protons.