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A BIOL1024 Part 2 > Oxidative phosphorylation > Flashcards

Oxidative phosphorylation Flashcards

1
Q

What is oxidative phosphorylation basically?

A

Transferring NADH from the cytoplasm to the mitochondrial membrane

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2
Q

Is Transferring NADH from the cytoplasm to the mitochondrial membrane direct and why?

A

No as no NADH transporters on the inner mitochondrial membrane

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3
Q

Where is the [NADH] greater. Matrix or cytoplasm?

A

Matrix> cytoplasm

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4
Q

What transports the NADH into the matrix?

A

Malate-Aspartate Shuttle- where energy requirements are relatively low
OR
Glyercol-Phosphate Shuttle

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5
Q

How many ATP is made from NADH using the malate-Aspartate shuttle?

A

3 ATP per NADH

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6
Q

Describe the malate-Aspartate shuttle

A

Transporters for Aspartate out the matrix into the cytosol and malate into the matrix from the cytosol.

Cycle of Aspartate to malate ( which moves into matrix) the malate to aspartate ( which moves into the cytosol)

Aspartate<=> Oxaloactate<=> Malate
w/ Transaminase and alpha-ketoglutarate-> glutamate

AND Malate dehyrogenase and NADH + H+ -> NAD+

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7
Q

Describe the glycerol-phosphate

A

Electrons from NADH used to reduce Dihydroxyacetone phosphate to glycerol 3 phosphate via Cytoplasmic glyercol-3-phosphate dehydrogenase
DHAP can go into glycolysis

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8
Q

When is the Glycerol-phosphate shuttle and malate-Aspartate shuttle used?

A

Glycerol-phosphate shuttle is for metabolically active tissues eg neurons or muscles

malate-Aspartate SHuttle is for low energetic tissues eg liver

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9
Q

How many ATP is produced in glycerol-phosphate shuttle

A

Cycle produces FADH2 so 2 ATP per NADH

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10
Q

Compare the 2 shuttles.

What is their Net ATP ranges

A

G-P shuttle = 36 ATP

M-A shuttle= 38 ATP

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11
Q

Compare the 2 shuttles. How many ATP are gained from the conversion of glyucose to pyruvate and the reoxidation of the 2 NADH produced

A

G-P shuttle = 6 ATP

M-A shuttle= 8 ATP

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12
Q

What are the major sources of NADH/FADH2?

A

Glycolysis
TCA cycle
Beta-oxidation of fatty acids

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13
Q

Where is FADH2 made?

A

FADH2 is made on the inner membrane
Succinate -> fumarate
The succinate dehydrogenase sits in this membrane and is also a component of the electron transport chain

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14
Q

How does pyruavte enter the inter mitochondrial space

A

MPC

Mitochondrial pyruvate carrier

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15
Q

Are oxidative reactions exergonic or endogenic?

A

Exergonic

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16
Q

What reaction is coupled to the energy generated as electrons passed from NADH/FADH2?

What does this reaction generate

A

Coupled to transport of H+ from to mitochondrial matrix to the intermembranous space via the ATP Synthase which aids the production of ATP

this generates an electrochemical gradient across the highly impermeable inner membrane

17
Q

What does the electrochemical gradient consist of?

A

Electrochemical gradient has an electrical (charge separation) and a chemical (concentration gradient) component

18
Q

What is direct transfer of electrons to oxygen not used?

What happens instead?

A

This would produce too much energy to be used all at once.
So electrons are transferred from one acceptors to another, releasing some energy at each stage

the work is used to pump protons across the membrane and the electrochemical gradient is used to generate ATP

19
Q

What is the final acceptor on oxidative phosphorylation?

A

Oxygen

2H+ +2 e + 1/2 O2 -> H2O

20
Q

Describe the structure and function of a proton pump

A

Greater [H+] in the intermembranous space than the matrix

In the matrix there is a high affinity binding site with -Ve charges from aa side chains.
The opening and closing of the gates as well as the conformational change required to release the H+ from its site is driven by the energy of the electron transfer.
Now the affinity is low hence H+ release.

21
Q

How many complexes are in the ETC?

A

5

22
Q

Describe Complex I

What is its other names?
What is its role?
What is this accompanied by?

A

Also called NADH ubiquinone reductase or NADH-Q reductase
It oxidises NADH and transfers 2 electrons to the mobile carrier ubiquinone.

This is accompanied by the transfer of approximately 4 protons across the inner mitochondrial membrane.
Reduced ubiquinone, called ubiquinol (QH2), is free to move throughout the inner membrane.
QH2 next delivers its electrons to complex III (NOT complex II).

23
Q

Describe Complex II

What is its other names?
What is its role?

A

Called Q-cytochrome-c oxidoreductase
Complex III transfers the electrons between two mobile electron carrier.
It receives them from QH2 and transfers them to soluble cytochrome-c , located in the intermembraneous space.
1 electron is transferred to 1 cytochrome-c with the transfer of approx. 2H+. Thus there are a total of 4H+ transferred.

24
Q

Describe Complex IV

What is it also called?
What is its role?
What it is accompanied by?

A

Also called cytochrome oxidase
This transfers the two electrons from the cytochrome-c proteins to the mitochondrial matrix.
This is accompanied by the transfer of 2 protons to the intermembraneous space and reducing oxygen on the matrix side to produce H2O.

25
Q

The oxidation of one NADH results in the transfer of aprrox how many H+ to the intermembranous space

A

10 H+

26
Q

Where does the oxidation of FADH2 occur?
Which complexes?

What is this also known as?

A

Complex II,III,IV

Also known as succinate dehydrogenase or succinate-Q reductase.

27
Q

FADH2 to FAD produces how many ATP?

A

2 ATP

28
Q

Describe the structure of the ATP Synthase

A

Head is a heterohexamer made up of 3 Alpha and 3 beta subunits.

Central rotator stalk (gamma subunit) has a protrusion. As this rotates it moves the alpha and beta domains in a conformational change.

29
Q

What is the L and T and O state of ATP synthase?

A

L=loose state- binds ADP and Pi tightly

T=tight state- binds ATP more tightly than ADP

O = open state- can bind ATP or ADP loosly

30
Q

What is the role of the alpha and gamma subunits in ATP synthase

A

Alpha- can bind ATP but dont participate in catalysis.

Gamma- rotation interconverts the T L and O states of the 3 Beta subunits

31
Q

How does ATP synthase work?

A

H+ passage makes gamma subunit spin between T L and O state which binds ATP, stabilises transition state for phosphoanhydride bond formation and releases ATP

32
Q

What requires the energy in the synthesis of ATP?

A

It is not the synthesis of ATP but the unbinding that requires energy

33
Q

True or False

1) ATP cannot be stored only made on demand
2) ATP is the fuel within a cell and between cells
3) ATP is made all the time
4) ATP needs specific transporters?

A

1- true
2- false only within the cell
3- false only when it is needed
4- true

34
Q

What drives ATP/ADP movement?

A

It is the voltage gradient that drives ATP/ADP movement as -4 charge on ATP prefers to move out while the -3 ADP moves into the matrix.

35
Q

What happens when there is no demand for energy?

A

ATP not hydrolysed so ADP levels low

Low ADP means H+ cannot return to mitro. matrix and ATP stuck in the matrix

A BIOL1024 Part 2 (18 decks)

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