terminal respiration

Question 1

What do all metabolic pathways lead to the production of?

Answer 1

reduced reactants that act as electron carriers e.g. NADH & FADH2

Question 2

what is the mitochondria the site of?

Answer 2

oxidative phosphorylation in eukaryotic cells

Question 2

what do these carriers do?

Answer 2

they make reduced anabolic products or biosynthetic precursors

go through cycles of redox reactions to form ATP

Question 3

what 2 things do mitochondria allow??

Answer 3

the coupling of the oxidation of carbon fuels to ATP synthesis.

the utilisation of proton gradients to produce ATP (and lots of it).

Question 4

where do NADH and FADH2 have to be for oxidative phosphorylation to begin?

Answer 4

mitochondrial matrix

Question 5

what is a shuttle?

Answer 5

it is used to move reducing equivalents across the mitochondrial membrane

Question 6

what is the glycerol 3 phosphate shuttle/

Answer 6

it allows the NADH synthesized in the cytosol by glycolysis to contribute to the oxidative phosphorylation pathway in the mitochondria to generate ATP.

This happens when NADH reduces Dihydroxy acetone phosphate (DHAP) to Glycerol 3-phosphate (G3-P)

G3-P then passes its electrons to FAD → FADH2 in the mitochondrial matrix

Question 7

how is an energetic price paid through cytosolic NADH using the Glycerol phosphate shuttle?

Answer 7

Because NADH passes its electrons to FADH2

And the Oxidation of FADH2 yields less ATP than the Oxidation of NADH

Question 8

what is the electron transport chain?

Answer 8

A game of hot potato (using electrons) passing them around 4 complexes until it reaches O2 as the final electron acceptor to make H2O

While creating a proton concentration gradient (C1 & C3 & C4) between the matrix and the intermembrane.

Question 8

describe complex I - NADH-Q oxidoreductase (NADH D.H.):

Answer 8

oxidation of NADH:

Reduction of Flavin mononucleotide (FMN) → FMNH2

FMNH2 passes 2e- to ubiquinone (Q) → ubiquinol (QH2)

Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)

Question 9

describe Complex II - Succinate-Q reductase (Succinate D.H.) (Same in Krebs Cycle):

Answer 9

Oxidation of FADH2 → FAD

Reduction of (FMN) → FMNH2

FMNH2 passes 2e- to Q → QH2

Doesn’t pump H+

Question 10

describe Complex III - Q-cytochrome c oxidoreductase:

Answer 10

Oxidation of ubiquinol (QH2) → ubiquinone (Q)

Reduction of Cyt-c molecules

Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)

Question 11

describe Complex IIII - Cytochrome C oxidase

Answer 11

Oxidation of Cyt-c molecules

Reduction of 1/2 O2

Then 1/2 O2 + 2H+ = H2O

Pumps H+ ion into the intermembrane space (HIGH ENERGY TRANSITION TO LOW ENERGY)

Question 12

what is ubiquinone/ coenzyme Q10/ Q10?

Answer 12

a coenzyme present in the electron transport chain with 10 isoprene repeats.

It is a dietary supplement that reduces free radicals and acts as an antioxidant.

Question 13

what is chemiosmosis?

Answer 13

the movement of protons from the mitochondria matrix to the intermembrane of the mitochondria as electrons pass through the complexes of the transport chain.

When the protons flow back down their gradient into the matrix they release energy to do work which is usually stored in the form of ATP, it is known as {{c1::proton motive force}}

Question 14

what is ATP synthase?

Answer 14

a large multi-unit protein complex that allows protons from the mitochondrial intermembrane to pass through, releasing energy that is stored in the form of ATP (ADP + Pi → ATP).

This is the final step in metabolising the food molecules we eat into energy

• It can produce one ATP for every 3 H+ it moves back into the matrix across the membrane

Question 15

what are the 2 parts of ATP synthase?

Answer 15

F0 – membrane bound proton conducting unit

– 10 subunits
– Separate subunit connects F0 to F1

F1 – protrudes into the mitochondrial matrix and acts as the catalyst for ATP synthesis

– Produces lots of ATP from the proton motive force energy collected by F0

Question 16

what’s the importance of the conformational changes (Binding Change Mechanism) in ATP Synthase? and how are they produced?

Answer 16

Conformational changes in the beta subunits of F1 catalyse the ADP → ATP conversion and release ATP.

They are produced by the rotation of the F0 cylinder and gamma shaft.

Question 17

describe the typical enzyme reaction with ATP:

Answer 17

As long as ATP is still bound to the enzyme, it stays on a low potential energy.

However, detaching the ATP of the enzyme requires high energy.

Which comes from the proton motive force. (proton gradient)

It shows that the proton motive force drives the release of ATP and not the formation of ATP.

Question 17

Describe what is meant by ‘electron transport chain is uncoupled to ATP synthase’

Answer 17

The electron transport chain is uncoupled to ATP synthesis if:

• The inner mitochondria membrane becomes permeable to protons, so the proton gradient cannot be generated.
• If this happens the electron transport chain still works, with O2 being reduced to H2O, but no ATP is made.

Question 18

Why does an FADH2 molecule produce less ATP than NADH?

Answer 18

Because FADH2 feeds in at Complex II, so only two sites that move protons across the membrane are utilised. (1.5 mol of ATP)

Because NADH feeds in at Complex I, so three sites are utilised. (2.5 mol of ATP)

Question 18

Give an example of a disease where the ‘electron transport chain is uncoupled to ATP synthase’

Answer 18

A disease: Malignant hyperthermia

• It is a disease caused by ‘leaky’ mitochondrial membranes that uncouple electron transport and ATP synthase.

Question 19

what is the proton gradient responsible for?

Answer 19

the coupling of the oxidative process with the ADP phosphorylation process.

Question 19

what does norepinephrine trigger?

Answer 19

triggers coupling the oxidative process with the ADP phosphorylation process.