Lecture 33: Oxidative Phosphorylation: ATP synthesis and regulation

Question 1

What are the two main parts of ATP synthase?

Answer 1

F0-intergral transmembrane part

F1-knobby parts that sticks into the mitochondrial matrix

Question 2

ATP synthase function parts

Answer 2

Rotor

Stator

Question 3

Rotor

Answer 3

comprised of:

• c subunits (10 to 14)
• E subunit
• Y subunit

all of these subunits rotate together when protons move one at a time from the P side to the N side

• always turns in the same direction
• is energized by the proton-motive force at each B subunit
• wholve revolution of rotor to produce One ATP

Question 4

Stator

Answer 4

Comprised of:

• b2 subunits
• S subunit
• hexamer of a-b-subunits

entire complex is fixed in the membrane and cannot rotate with the rotor

Question 5

How does ATP synthase work?

Answer 5

The c subunit complex rotates in the membrane as H+s move from the P to the N side of the inner membrane

Question 6

Y subunit works by

Answer 6

y subunit of the rotor rotates with the c subunits

• sticks into the center of the hexameter complex made up of the a-b-pairs
• assymetric and as induces a conformational change in the B-conformatoion as it rotates past a B subunit of each a-B pair

Question 7

Types of conformations from ATP symthase

Answer 7

Open
loose
tight

Question 8

Open conformation

Answer 8

dissociation of ATP and allow association of ADP and Pi

Question 9

Loose conformation

Answer 9

ADP and Pi bound and reaction

Question 10

Tight conformation

Answer 10

ATP bound

Question 11

how many protons are used for each ATP synthesized?

Answer 11

3

Question 12

Issues concerning transport of metabolites though the mitochondrion

Answer 12

• none of the molecules ADP, Pi, or ATP are freely diffusing through the inner membrane- NEEDS TO BE A WAY TO GET ADP AND Pi into the matrix and ATP out
  2) Two NADH molecules are made in the cytoplasm from each glucose during glycolysis. NADH cannot freely diffuse through the mmembrane SO NEEDS A WAY TO GET NADH INTO THE MATRIX

Question 13

Solution to get ADP and Pi into the matrix

Answer 13

Adenine nucleotide transporter
Pi Transporter

BOTH cost the cell the equivalent of one proton that would otherwisee would be available for ATP synthesis

Question 14

Adenine Nucleotide transporter

Answer 14

antiport translocase

• moves ADP^3- into the matrix and ATP^4- out of the matrix
• exchange is drive by the higher negative charge in the matrix thane the inter membrane space

Question 15

Pi Transporter

Answer 15

Pi and H+ are moved together

• doesn’t change the amount of charge
• does change pH

Question 16

NADH movement into the matrix

Answer 16

Malate-aspartate shuttle is used

Question 17

malate-aspartate shuttle

Answer 17

two antiports are involved:

• malate/a-ketogluterate antiport
• aspartate/glutamate antiport

-6 total reacotns

Question 18

What does the malate-aspartate shuttle result in?

Answer 18

the moment of one NADH equivalent from the cytoplasm into the matrix

Question 19

What are the two key reactions of the malate-aspartate shuttle

Answer 19

• oxidation of malate to oxaloacetate in matrix

- reduction of oxaloacetate to malate in cytoplasm

Question 20

Glycerol phospahte shuttle

Answer 20

Getting reducing equivalents into the matrix

• NADH is oxidized by dihydroyaceton phosphate to produce glycerol 3-phosphate in inter-membrane space
• Glycerol 3-phosphate on the inner membrane is oxidized and produces FADH2
• FADH2 in the membrane is oxidized to produce FADH2 in the membrane
• FADH2 feeds complex III

Question 21

Hypoxia dangers

Answer 21

low O2 concentration and pressure

1) respiration cannot occur because of lo2 pO2 and cells suffer ATP deficiency
2) without high enough O2 in complex III, there is accumulation of free radicals
- radical FADH- reacts with O2 to create a reactive oxygen species-radical O2- is extremely damaging to proteins and nucleic acids

Question 22

Reactive oxygens species (ROS)

Answer 22

radicals OH and O2

Question 23

Mechanisms to avoid Hypoxia

Answer 23

1) Glycolysis increase, but entry of pyruvate into the TCA cycle is inhibited, and ATP is produced anaerobically
2) Reduction in the citric acid cycle reduces electron flow through oxidative phosphorylation
3) A more effective Cox 4-2 subunit (part of complex IV) is mobilized