Terminal Respiration

Question 1

what is a hexos

Answer 1

A sugar/sacharride containing 6C’s

Question 2

What can NAD+/FAD be classed as

Answer 2

Co-reactants - which are reduced by H- (hydride) ions containing high E electrons to form NADH/FADH2

Question 3

What can then happen with NADH/FADH2?

Answer 3

• Used in anabolism
• Pass their High E e- through series of carrier P to yeild lots of ATP (term resp, oxi phosp, e- trans chain). High E e- eventually combine with O2 and form H2O

Question 4

Where does oxidative phosphorylation occur in eukaryotes

Answer 4

Mitochondria

Question 5

What’s the puropose of the mitochondria in relation to oxidative phosphorylation?

Answer 5

Allows coupling of oxidation of carbon fules to ATP sysnthesis
utilises proton gradients to produce ATP

Question 6

Where must NADH/FADH2 be for terminal respiration

Answer 6

mitochondrial matrix

Question 7

Where is the majoriyt of NADH/FADH2 formed

Answer 7

in mitochondrial matrix (e.g. CAC and B-oxiation of FA

Question 8

Where else can NADH be formed

Answer 8

In the cytoplasm from glycolysis

Question 9

How do we move cytoplasmic NADH into the mitochondrial matrix?

Answer 9

Shuttle used to move reducing equivalents accross the mitochondrial membrane (as cytoplasmic NADH can’t cross), but FADH2 can pass it’s e- onto the ETC withing the mitochondria. Process called glycerol phosphate suttle - reversiable oxidative process

Question 10

Explain the glycerol phosphate shuttle

Answer 10

1. NADH can’t cross mitochondrial membranes
2. becomes oxidised to NAD+, reducing Dihydroxy acetone phospate to G3P
3. G3P passes these e- across the membrane onto FAD, forming FADH2
4. FADH2 can then be oxidised in the ETC

see sheet

Question 11

How much energy is released by the osidation of FADH2 relative to NADH

Answer 11

Per mol, less ATP is generated by oxidation of FADH2 than NADH in the ETC. This means an energetic price is paid for using cytostosolic reduced co-substrates in terminal respiration

Question 12

What does the ETC contain (name each)

Answer 12

4 complexes:
1. NADH-Q oxidoreductase
2. Succinate-Q reductase
3. Q-cytochrome c oxidoreductase
4. Cytochrome c oxidase

Question 13

What does complex 1 NADH-Q oxidoreductase do?

Answer 13

Oxidises NADH and passes high-E e- to ubiquinone to give ubiquinol (QH2). Pumps H+ ions into the intermembranse space

Question 14

What does complex 2 Succinate-Q reductase do?

Answer 14

Oxidises FADH2 and like 1 passes high-E e- to ubiquinone to give ubiquinol (QH2). Enzyme also part of CAC under guise of succinate dehydrogenase

Question 15

What is Ubiquinone (Q)

Answer 15

• Called Q10 in mitochondria (as has 10 isoprene repeats)
• AKA coenzymeQ10
• Dietary supplement - reduces free radicals so acts as antioxidant

Question 16

What does complex 3 Q-cytochrome c oxidoreductase do?

Answer 16

• Take e- from ubiquinol (QH2) annd passes them to cytochrome c (like heam)
• 1 Qh2 is oxidised to yeild 2 reduced cytochrome c moleules
• Pumps protons into intermembrane space

Question 17

What does complex 4 Cytochrome c oxidase do?

Answer 17

• Take e- from cytochrome c and pass them to O2
• e- channeled through Fe-Cu centre
• Pumps protons into intermembrane space

Question 18

Where do NADH and FADH2 come from?

Answer 18

• NADH: glycolysis, CAC, B-oxidation
• FADH2: B-oxidation, (and HADH via G3P shuttle)

Question 19

how is energy conserved from the breakdown of food molecules

Answer 19

Ultimately leads to oxidation of NADH, FADH2, ubiquinone and cytochrome c. Energy further conserved through proton gradient across inner mitochondrial membrane

Question 20

How is enery stored up in proton grads used?

Answer 20

1. Electron Motive Force - (actually proton motive force) - allows proton gradient to work
2. A molecular turbin has evolved to harness the E in the proton gradient - ATP synthase

Question 21

Define Chemisosmosis and proton-motive force

Answer 21

• As e- pass through complexes of the transport chain, protons move from matrix to outside of inner mitochondrial membrane - chemiosmosis
• This movement has particular spatial directionality, so is classed as “vectoral”. Ex of energy transformation.
• Protons on outside of membrane act as a store of Ep
• When they are “allowed” to flow back down their grad they release E - Proton motive force

Question 22

Explain the process of ATp synthesis

Answer 22

1. protons eventually flow down their conc grad back into the mitochondrial matrix
2. Only a relatively small number of sites exist on membrane where this happen
3. At these sites, multi-unit P called ATPsynthase (ATPase) is found
4. ATPase has mechanism to allow protons to pass through
5. As they flow, E stored in gradient used to Convert ADP+Pi to ATP
6. ATP then stores this Ep and uses it to dow work in cells

Question 23

What is the structure of ATP synthase like?

Answer 23

Has 2 parts:
1. F0 - membrane bound proton conducting unit (10 subunits)
2. F1 - protudes into the mitochoindrial matric and acts as catalyst for ATP syntheses - produces lots of ATP from P-motive force energy collected by F0

Question 24

How does ATP synthase work?

Answer 24

1. ADP+Pi enter B subunit
2. Rotation of F0 cylinder and y shaft causes **conformational ** changes in B subunits of F1
3. Catalyses ADP->ATP conversion and release ATP

Question 25

Explain the binding change mechanis of ATPase (briefly)

- not in course?

Answer 25

Sequential conformationsal changes of B subunit - 3 different binding pockets in 3 different states
By rotaion of F0 cylinder and y shaft all binding pockets run cyclic through the 3 states

Question 26

Why does NADH produce more ATP than FADH2 - stochiometry of oxidative phosphorylation

Answer 26

As e- pass through ETC, complexes 1,3,4 move total of 8H+ from matrix to outside of membrane. ATPase can produce 1ATP per 3H+ it moves back into the matrix across the membrane.

NADH feeds in at Complex 1 meaning e- pass through all 3 sites aloowing proton movement (Complex 1,3,4)
FADH2 feed in at Complex 2 so only 2 sites where protons move across the membrane are utilised,
Thus, 2.5mol and 1.5mol of ATP generated per mol of NADH and FADH2 respectively

Question 27

What are the products of respiration?

Answer 27

Food molecules completely broken down to CO2, H2O (and energy)
Some Ep from food molecules “saved” (after being transformed through reduced co-reactants and the terminal respiratory system) and is used to make ATP

Question 28

What is electron transport said to be coupled to?

Answer 28

ATP synthesis (coupled oxidative phosphorylation)

Question 29

What happens if e- transport is not couples to ATP synthesis?

Answer 29

If inner mitochondrial membrane becomes permeable to protons: proton grad not generated.
E- transport still occur (O2 reduced to H2O) but no ATP made.
Energy released from e- passing along the terminal respiratory system doesn’t make ATP bu is released as heat

Question 30

What diesase is caused from uncoupled e- transport and ATP synthase

Answer 30

Malignant hyperthermia - “leaky” mitochondrial membranes

Question 31

When could intentional uncoupling occur?

Answer 31

brown fat in newborn infants - cells have many mitochondria and if baby cold, nor-epinephrine triggers opening of channel protien called thermogenin which sits on inner mitochondrial membrane of brown fat cells - releases heat

Question 32

What does the proton gradient act as/do?

Answer 32

Store of energy and drives production of lots of ATP

Question 33

What 2 states can oxidative phosphorylation be?

Answer 33

Coupled or uncoupled

Question 34

What can coupling or uncoupling be a result off?

Answer 34

Intentionally or in disease states

Question 35

What is the final electron acceptor

Answer 35

Oxygen (forms 2 H20)

Question 36

2 parts of oxidative phosphorylation

Answer 36

• Electron transport chain - first 4 proteins
• Chemiosmosis - ATPsynthase part