Cell Integrity

Question 1

What is complex I of the Oxidative phosphorylation membrane proteins?

Answer 1

NADH -Q oxidoreductase / NADH dehydrogenase

Question 2

What is complex II of the Oxidative phosphorylation membrane proteins?

Answer 2

Succinate- Q reductase / succinate dehydrogenase

Takes FADH

Question 3

What is complex III of the Oxidative phosphorylation membrane proteins?

Answer 3

Q- cytochrome C oxidoreductase

Question 4

What is complex IV of the Oxidative phosphorylation membrane proteins?

Answer 4

cytochrome C oxidase (Oxygen accepts final electron and becomes H2O)

Question 5

What Mobile carriers are a part of the Oxidative Phosphorylation chain? And where are they in the chain?

Answer 5

Co-enzyme Q (ubiquinone) comes between II / I and III and Cytochrome C comes between III and IV

Question 6

What is a redox potential?

Answer 6

The ability of a redox couple to accept or donate electrons is known as the reduction potential

Question 7

What has a Negative E0 value and what does that mean?

Answer 7

A redox couple tends to donate electrons hence having more reducing power than hydrogen.
E.g. NAD+ and NADH = -0.32 V

Question 8

What has a Positive E0 value and what does that mean?

Answer 8

Redox couple tends to accept electrons and hence has more oxidising power than hydrogen e.g. 1/2 O2 + 2H+ / H2O = +0.82

Question 9

What are the F0 and F1 parts in relation to ATP synthase?

Answer 9

F0 - membrane bound part, F1 - projects into the matrix space. rotation of enzyme drives transition states. energy flows from catalytic subunit into bound ADP and Pi to promote the formation of ATP

Question 10

What is an Oxygen electrode used for?

Answer 10

Creates a current which is proportional to the oxygen concentration in the sample chamber. Can dissect various components of the e transport chain

Question 11

What is the most common cause of failure of the oxidative phosphorylation chain?

Answer 11

Hypoxia/Anoxia - lack/loss of oxygen. ATP is limited to 250g at a time so needs to be recycled 300x. This can be compromised.

Question 12

What is respiratory control?

Answer 12

Allows the body to adapt oxygen consumption to actual energy requirements.

Uptake of O2 by mitochondria is controlled by Inorganic phosphate and ADP

Question 13

What poisons bind with ferric haem group in cytochrome oxidase?

Answer 13

Cyanide, Azide. Blocks final step of ETC by binding to ferric form of haem group in cytochrome oxidase. high affinity for Fe3+

Question 14

Which poison as competitive inhibitor of succinate dehydrogenase?

Answer 14

Malonate, resembles succinate. slows down flow to e- from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate

Question 15

What is Rotenone?

Answer 15

Isoflavone found in roots and seeds. Inhibits e transfer from Complex I to Ubiquione

Question 16

What are the Oxygen Electrode equations?

Answer 16

O2 + 4H+ + 4e- → 2 H2O

4 Ag+ + 4Cl- → AgCl + 4e-

Question 17

What antibiotic is produced by Streptomyces and acts as a poison?

Answer 17

Oligomycin

inhibits Oxidative phosphorylation by binding to ATP synthase, blocking flow of protons through enzyme

Question 18

What is Dinitrophenol DNP?

Answer 18

A proton ionophore which can shuttle protons across the inner mitochondrial membranes. uncoupling OP from ATP production

Question 19

How does DNP induce weight loss?

Answer 19

Increases metabolic rate and body temperature. Slimming dose and dose to kill was too close.

Question 20

Mitochondria

Answer 20

Mitochondria have an outer membrane (which limits the size of the organelle) and an inner membrane (folds that project inward called cristae). The reactions of oxidative phosphorylation take place in the inner membrane, in contrast to the Krebs Cycle reactions which occur in the matrix. Numerous folds within the cristae increase the surface area upon which oxidative phosphorylation can take place.



Question 21

Overall reactions of co enzyme NADH FADH re-oxidation?

Answer 21

NADH + H+ + ½ O2 → NAD+ + H20
FADH2 + H+ + ½ O2 → FAD + H20
Each reaction has a ΔG of -223 and -170 kJ/mol respectively.



Question 22

Oxygen electrode :?

Answer 22

The base of the chamber is formed by a teflon membrane permeable to oxygen. Underneath this membrane, is a compartment containing two electrodes, a Platinum (Pt) cathode and a silver (Ag) anode.

A small voltage of around 0.6 volts is applied between the anode (+) and cathode (-). Oxygen diffuses through the teflon membrane and is reduced to water at the platinum cathode:

O2 + 4H+ + 4e- → 2 H2O
The circuit is completed at the silver anode, which is slowly oxidised to AgCl by the KCl electrolyte.

4 Ag0 + 4Cl- → AgCl + 4e-
The resulting current is therefore proportional to the oxygen concentration in the sample chamber.

We can use the oxygen electrode to dissect various components of the electron transport chain.

Question 23

Facts about ATP requirements?

Answer 23

A sedentary male of around 70 kg (154 lbs) requires about 8,400 kJ for a day’s worth of activity, which equates to 83 kg of ATP.

Each of these ATP molecules has a lifespan of between 1-5 mins.

Humans possess only about 250 g of ATP at any given moment with each ATP molecule recycled approximately 300 times per day.

Consequently, any interruption to the process of oxidative phosphorylation /ATP synthesis, means that a cell rapidly becomes depleted of ATP and is likely to die.
The most common cause of a failure of oxidative phosphorylation is simply a lack of oxygen e.g. hypoxia (diminished), anoxia (total).

Depending on the cell type and their metabolic requirements, death will be within a few minutes (neurons) or a few hours (muscle).