Cell Integrity Flashcards
Where is the bulk of cellular ATP generated?
During oxidative phosphorylation in the inner membrane
Where does the Krebs cycle take place?
The matrix of the mitochondria
What is the equation for the re oxidisation of NADH?
NADH + 1/2 O2 + H+ —>
NAD+ + H2O
DG= -223 kJ/mol
What is the equation for the re oxidisation of FADH2?
FADH2 + 1/2 O2 + H+ —>
FAD + H2O
DG= -170 kJ/mol
How many and what type of electron carriers does the electron transport chain consist of?
4 membrane proteins
2 mobile
What are the four membrane proteins in the ETC?
Complex I
NADH dehydrogenase
Complex II
Succinate dehydrogenase
Complex III
Q-cytochrome C oxidreductase
Complex IV
Cytochrome C oxidase
What are the two mobile carriers involved in the electron transfer chain?
Co enzyme Q (ubiquinone)
Cytochrome C
What do complexes I II and IV do in terms of electrons?
Accept them, and in doing so a proton (H+) is pumped into the inter membrane space
What is the role of Succinate dehydrogenase (complex II)?
It is an enzyme of the TCA cycle and sits in the inner mitochondrial membrane. It uses FAD as a cofactor and communicates directly with coenzyme Q.
Electrons are passed from FADH2 to coenzyme Q it also picks up a pair of protons, regenerating FAD and forming QH2
Does FADH2 or NADH release more protons into the inter membrane space when re oxidised?
NADH
Where do NADH and FADH2 enter the electron transport chain?
NADH at complex I
FADH2 art complex II
What is the ability of a redox couple to accept/donate electrons called?
Redox potential
What does a negative standard redox potential (E0) imply
The redox couple has the tendency to donate electrons and therefore has more reducing power than hydrogen
What does a positive E0 imply?
The redox couple has the tendency to accept electrons and there has a greater oxidising power than hydrogen
ATP synthase is a multimedia enzyme consisting of two parts. What are these?
F0 : membrane bound
F1 : projects into the matrix
What does the oxygen electrode do?
Measures the oxygen concentration in a solution housed within a small chamber
What is the oxygen electrode made of?
The base is a Teflon membrane permeable to oxygen. Below this there is a compartment containing a platinum cathode (-ve) and a silver anode (+ve)
What happens when around 0.6 V is applied? (Include equations at the anode and cathode)
Oxygen diffuses through the Teflon and is reduced to water at the cathode:
O2 + 4e- + 4H+ —> 2 H2O
The circuit is completed at the anode which is slowly oxidised to AgCl by the KCl electrolyte:
4Ag+ + 4Cl- —> 4AgCl + 4e-
The resulting current is proportional to the oxygen concentration
Rough how many grams of ATP do humans possess at a time?
250g
It is recycled ~300 times a day
What is respiratory control?
The control of the uptake of oxygen by mitochondria due to the concentrations of ADP and Pi
What are metabolic poisons?
Molecules that interfere with either the flow of electrons along the ETC or the flow of H+ through ATP synthase
How do cyanide and azide act as metabolic poisons?
They bind with high affinity to the ferric form of the harm group in the cytochrome oxidase complex plucking the final step of the ETC
How does Malonate act as a metabolic poison?
It’s shape closely resembles that of succinate so it acts as a competitive inhibitor of succinate dehydrogenase. It slows down the flow of electrons from succinate to ubiquinone
How does rotenone act as a metabolic poison?
It’s an isoflavone found in the roots and seeds of some plants. It inhibits the flow of electrons from complex I to ubiquinone
How does oligomycin act as a metabolic poison?
It is an antibiotic produced my streptomyces that binds to the stalk of ATP synthase blocking the flow of protons through the enzyme
How does dinotrophenol (DNP) act as a metabolic poison?
It is a proton ionophore which can shuttle protons across the inner mitochondrial membranes
