Terminal Respiration

Question 1

Where is the only site of oxidative phosphorylation in eukaryotes?

Answer 1

The mitochondria

Question 2

Where do NADH and FADH have to be for oxidation in the terminal respiratory system?

Answer 2

Mitochondrial matrix

Question 3

How does the NADH and FADH that is formed in the cytosol reach the mitochondrial matrix?

Answer 3

• The glycerol phosphate shuttle is used to move reducing equivalents across the membrane
• Cytoplasmic NADH cannot cross the membrane but FADH can pass on its electrons on to the electron transport chain within the mitochondria.

Question 4

How does the e’s of NADH get across the membrane of the mitochondria is it cannot cross the membrane?

Answer 4

Glycerol 3 Phosphate can cross the membrane and passes its e’s to FADH

Question 5

What is the generation of ATP of FADH compared to NADH?

Answer 5

Less

An energetic price is paid for using cytosolic reduced co-substrates in terminal respiration

Question 6

What is the name of complex I?

Answer 6

NADH-Q oxioreductase

Question 7

What is the name of complex II?

Answer 7

Succinate-Q reductase

Question 8

What is the name of complex III?

Answer 8

Q Cytochrome C oxioreductase

Question 9

What is the name of complex IV?

Answer 9

Cytochrome C oxidase

Question 10

What happens at complex I?

Answer 10

• NADH is oxidised and e’s are passed to ubiquinone to give uniquinol (QH2)
• H ions are pumped into the intramembrane space

Question 11

What happens at complex II?

Answer 11

-FADH2 is oxidised and e’s are passed to ubiquinone to give ubiquinol

Question 12

What is uniquinone?

Answer 12

Dietary supplement believed to reduce free radicals and thus acts as an anti-oxidant

Question 13

What happens at complex III?

Answer 13

• Passes the e’s form ubiquinol to cytochrome C
• 1 ubiquinol is oxidise to yield 2 reduced cytochrome C molecules
• Pumps protons into the intermembrane space

Question 14

What happens at complex IV?

Answer 14

-Takes e’s from cytochrome c and passes them to molecular O2 to form H2O
-e’s channelled through Fe-Cu centre
Pumps protons into the intermembrane space

Question 15

What does the conservation of energy from the breakdown of food molecules ultimately lead to?

Answer 15

The oxidation of NADH,FADH2, ubiquionone and cytochrome C

Question 16

How is energy further conserved?

Answer 16

By the setting up of a proton gradient across the inner mitochondrial membrane

Question 17

How is the energy stored up in the H gradient used?

Answer 17

• The EMF acts as a proton motive force and allows the proton gradient to work
• A molecular turbine has ebeolved to harness the energy in the proton gradient-ATP synthase

Question 18

What is chemiosmosis?

Answer 18

As e’s pass trough the complexes of the transport chain protons move from the matrix to the outside of the inner mitochondrial membrane

Question 19

Why is the movement of protons across the mitochondrial inner membrane classed as vectoral?

Answer 19

It has a particular spatial directionality

Question 20

Why is the movement of protons across the mitochondrial inner membrane class as an energy transformation?

Answer 20

• The protons on the outside of the membrane act as a store of potential energy
• When these protons are allowed to flow back down their gradient they release energy to do work known as the proton motive force

Question 21

What happens at the sites where protons flow down their concentration gradient back to matrix of the mitochondria?

Answer 21

A large multi-unit protein complex called ATP synthase is found.

• It has a mechanism which allows protons to flow through it.
• As they flow through ATPase, the energy stored in the gradient is used to make ATP from ADP and Pi

Question 22

What are the 2 parts of ATPase?

Answer 22

• F0

- F1

Question 23

What is F0 ?

Answer 23

It is a membrane bound protein conducting unit made of 10 subunits

Question 24

What does F1 do?

Answer 24

• It protrudes into the mitochondrial matrix and acts as the catalyst for ATP synthesis.
• It produces lots of ATP from the proton motive force energy collected by F0

Question 25

How is the reaction ADP>ATP catalysed/

Answer 25

• ADP and Pi enter a B subunit

- The F0 cylinder and the y shaft forces conformation changes in the B subunits of F1 that catalyse the reaction

Question 26

What does the proton gradient force do in relation to ATP?

Answer 26

Drives its release

Question 27

What happens in the binding change mechanism?

Answer 27

-Protons moves from positive side of the membrane to the negative side#
-Sequenctial conformational changes of B subunit
B subunit that binds ADP+Pi
-B subunit that binds ATP
-B subunit that doesn’t bind ATP

Question 28

Electron transport and ATP synthesis are said to be coupled but how do they become uncoupled?

Answer 28

• If the inner mitochondrial membrane becomes permeable to protons, the proton gradient cannot be generated-
• If this happens the elctron transport can still occur with O2 being reduced to H2O but no ATP is made

Question 29

What happens to the energy created by the transfer of e’s along the terminal respiration system?

Answer 29

Released as heat

Question 30

What is malignant hyperthermia?

Answer 30

A disease caused by leaky mitochondrial membranes that uncouple electron transport and ATPsynthase

Question 31

When is intentional uncoupling seen in humans?

Answer 31

• In the brown fat of newborns.
• Brown fat contains lots of mitochondria
• If a baby becomes cold, norepinephrine triggers the opening of a channel in a protein called thermogenin

Question 32

When is intentional uncoupling seen in plants?

Answer 32

• Arum lily to attract insects

- Skunk cabbage to mel the snow that covers it