Cell Integrity Flashcards
What is substrate level phosphorylation?
Production of ATP by the direct transfer of a high-energy phosphate group from an intermediate substrate to ADP
What is oxidative phosphorylation?
ATP is produced using energy derived from I the transfer of e- in an electron transport chain
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane
What are the overall reactions for the oxidation of NADH and FADH2 by oxygen in the mitochondria?
NADH + H+ +1/2O2 —> NAD+ + H2O
FADH2 + H+ + 1/2O2 —> FAD + H2O
What are the 4 membrane proteins in the ETC?
4 membrane proteins:
- complex I (NADH dehydrogenase)
- complex II (succinate dehydrogenase)
- complex III ( Q-cytochrome C oxidoreductase)
- complex IV (cytochrome c oxidase)
What re the two mobile carriers in the ETC?
Co-enzyme Q (ubiquinone)
Cytochrome C
How does the ETC work?
Complexes I, III and IV accept e- from the oxidation of NADH and FADH2 —> passed through the chain
As they pass they lose energy which is used to pump H+ into the intermembrane space
What happens in complex I?
NADH is oxidised (gives e- to the complex) and a H+ is pumped out
What happens in complex II?
FADH2 is oxidised and the complex takes an e- and passes it to coenzyme Q which picks up two protons and forms QH2
Why does NADH form 3ATP and FADH2 only 2ATP
FADH2 bypasses complex I so fewer protons are pumped into the intermembrane space
So fewer protons flowing through ATP synthase so less ATP generated
What is ATP synthase?
A sub unit protein that consistes of a F0 and F1 part
Where is F0 and F1 located?
F0 —> membrane bound
F1 —> projecting into the matrix space
How does ATP synthase work?
Protons flow into matrix —> drives rotational movement of F1
Altering affinities for ATP, ADP and Pi
—> conformational energy flows from the catalytic subunit into bound ADP+Pi to from ATP
Direction of proton flow dictates whether ATP is generated or consumed
What does an oxygen electrode do?
Measures O2 consumption
How does the oxygen electrode work?
O2 diffuses through the Teflon membrane and reduces water at the platinum electrode
Silver anode slowly oxidised to silver chloride by the KCl electrolyte
Resulting current is directly proportional to O2 conc. in sample chamber
How cane we analyse mitochondrial respiration with an oxygen electrode?
Place suspension of mitochondria in the chamber and start recording
Measure baseline respiration over a minute
Add ADP which will cause a lot of the O2 to be used up
Find the ratio of the amount of ADP phosphorylated to the amount of O2 consumption —> ADP-Oxygen index
After all ADP is used up —> restored basal respiration rate and O2 continuous to decrease until all used up
What is respiratory control?
Allows body to adapt O2 consumption to the actual energy requirements
What is a metabolic poison?
Molecule that interferes with either:
-floe of e- along the ETC
-flow of protons through ATP synthase
What do Cyanide and azide do?
Bind with high affinity to the ferric form of the haem group in the cytochrome oxidase complex
—> block flow of e- through the final step of the ETC
What does malonate do?
Closely resembles succinate —> competitive inhibitor
Slows down flow of e- from succinate to ubiquinone by inhibiting the oxidation of succinate to fumarate
What does dinitrophenol do?
Transports H+ across inner mitochondrial membrane
—> bypasses ATP synthase —> uncouples ATP production from proton pumping
—> increase metabolic rate and body temp
—> induces weight loss
What is non-shivering thermogenesis?
UCP-1 is activated in response to drop in core body temp
—> ATP synthase bypassed
—> much energy within the H+ gradient dissipated as heat
What does Rotenone do?
Inhibits transfer of e- from complex I or ubiquinone
What d’oies Oligomycin do?
Antibiotic
Binds to the stalk of ATP synthase
—> blocks flow of e- through the enzyme
