Cell Integrity Flashcards
What is complex I of the Oxidative phosphorylation membrane proteins?
NADH -Q oxidoreductase / NADH dehydrogenase
What is complex II of the Oxidative phosphorylation membrane proteins?
Succinate- Q reductase / succinate dehydrogenase
Takes FADH
What is complex III of the Oxidative phosphorylation membrane proteins?
Q- cytochrome C oxidoreductase
What is complex IV of the Oxidative phosphorylation membrane proteins?
cytochrome C oxidase (Oxygen accepts final electron and becomes H2O)
What Mobile carriers are a part of the Oxidative Phosphorylation chain? And where are they in the chain?
Co-enzyme Q (ubiquinone) comes between II / I and III and Cytochrome C comes between III and IV
What is a redox potential?
The ability of a redox couple to accept or donate electrons is known as the reduction potential
What has a Negative E0 value and what does that mean?
A redox couple tends to donate electrons hence having more reducing power than hydrogen.
E.g. NAD+ and NADH = -0.32 V
What has a Positive E0 value and what does that mean?
Redox couple tends to accept electrons and hence has more oxidising power than hydrogen e.g. 1/2 O2 + 2H+ / H2O = +0.82
What are the F0 and F1 parts in relation to ATP synthase?
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
What is an Oxygen electrode used for?
Creates a current which is proportional to the oxygen concentration in the sample chamber. Can dissect various components of the e transport chain
What is the most common cause of failure of the oxidative phosphorylation chain?
Hypoxia/Anoxia - lack/loss of oxygen. ATP is limited to 250g at a time so needs to be recycled 300x. This can be compromised.
What is respiratory control?
Allows the body to adapt oxygen consumption to actual energy requirements.
Uptake of O2 by mitochondria is controlled by Inorganic phosphate and ADP
What poisons bind with ferric haem group in cytochrome oxidase?
Cyanide, Azide. Blocks final step of ETC by binding to ferric form of haem group in cytochrome oxidase. high affinity for Fe3+
Which poison as competitive inhibitor of succinate dehydrogenase?
Malonate, resembles succinate. slows down flow to e- from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate
What is Rotenone?
Isoflavone found in roots and seeds. Inhibits e transfer from Complex I to Ubiquione
What are the Oxygen Electrode equations?
O2 + 4H+ + 4e- → 2 H2O
4 Ag+ + 4Cl- → AgCl + 4e-
What antibiotic is produced by Streptomyces and acts as a poison?
Oligomycin
inhibits Oxidative phosphorylation by binding to ATP synthase, blocking flow of protons through enzyme
What is Dinitrophenol DNP?
A proton ionophore which can shuttle protons across the inner mitochondrial membranes. uncoupling OP from ATP production
How does DNP induce weight loss?
Increases metabolic rate and body temperature. Slimming dose and dose to kill was too close.
Mitochondria
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.
Overall reactions of co enzyme NADH FADH re-oxidation?
NADH + H+ + ½ O2 → NAD+ + H20
FADH2 + H+ + ½ O2 → FAD + H20
Each reaction has a ΔG of -223 and -170 kJ/mol respectively.
Oxygen electrode :?
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.
Facts about ATP requirements?
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).
