Lecture 33: Oxidative Phosphorylation: ATP synthesis and regulation Flashcards Preview

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Flashcards in Lecture 33: Oxidative Phosphorylation: ATP synthesis and regulation Deck (23)
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1

What are the two main parts of ATP synthase?

F0-intergral transmembrane part
F1-knobby parts that sticks into the mitochondrial matrix

2

ATP synthase function parts

Rotor
Stator

3

Rotor

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

4

Stator

Comprised of:
-b2 subunits
-S subunit
-hexamer of a-b-subunits

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

5

How does ATP synthase work?

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

6

Y subunit works by

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

7

Types of conformations from ATP symthase

Open
loose
tight

8

Open conformation

dissociation of ATP and allow association of ADP and Pi

9

Loose conformation

ADP and Pi bound and reaction

10

Tight conformation

ATP bound

11

how many protons are used for each ATP synthesized?

3

12

Issues concerning transport of metabolites though the mitochondrion

-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

13

Solution to get ADP and Pi into the matrix

Adenine nucleotide transporter
Pi Transporter

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

14

Adenine Nucleotide transporter

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

15

Pi Transporter

Pi and H+ are moved together
-doesn't change the amount of charge
-does change pH

16

NADH movement into the matrix

Malate-aspartate shuttle is used

17

malate-aspartate shuttle

two antiports are involved:
-malate/a-ketogluterate antiport
-aspartate/glutamate antiport

-6 total reacotns

18

What does the malate-aspartate shuttle result in?

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

19

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

-oxidation of malate to oxaloacetate in matrix
-reduction of oxaloacetate to malate in cytoplasm

20

Glycerol phospahte shuttle

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

21

Hypoxia dangers

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

22

Reactive oxygens species (ROS)

radicals OH and O2

23

Mechanisms to avoid Hypoxia

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