Molecular Biology - Cell Integrity Flashcards
Anoxia
Total lack of oxygen
NADH reoxidation
NADH + H+ + 1/2O2 -> NAD+ + H2O
FADH2 reoxidation
FADH2 + 1/2O2 -> FAD + H2O
Delta G for ATP hydrolysis
-31 ; so energy released from cofactors can generate several phosphoanhydride bonds
OxPhos takes place in
Inner membrane
Krebs takes place
Mitochondrial matrix
OxPhos adaptation
Folds within Cristal increase SA
How many complexes in ETC
4
Mobile carriers of electrons
Co-enzyme q and cytochrome c
How does ETC work
Complexes 1, 3, 4 accept electrons and protons from aqueous solution - protons are pumped into inter membrane space simultaneously
Complex 2
Uses FAD as a cofactor and communicates directly with coenzyme Q ; FADH2 passes on two protons (and electrons) to Coenzyme Q - regenerate FAD and QH2 is formed
Why are fewer ATP molecules regenerated from FADH2 compared to NADH
In NADH electrons pass through complex 1 so more protons are pumped into inter membrane space = more ATP
Negative redox potential
Redox couples has a tendency to donate electrons and so has more reducing power than hydrogen - GETS OXIDISED - REDUCING AGENT
Oxygen and water redox
H2 + 1/2O2 -> H2O
Transfer of electrons from one complex to the next
As electrons pass along they lose energy which is used to pump protons into intermembrane space
ATP molecule lifespan
Between 1-5 minutes
How much ATP do humans contain?
250g and each ATP molecule recycled 300 times
How much ATP does a sedentary human require per day?
83 kg
How quickly is cell death
A few minutes for neurons and a few hours for muscle
Transfer of electrons from one complex to another?
Energetically favourable
ATP synthase is made of?
F0 and F1 area
F0 = a, b and c
F1 = a, b and g
Each consists of three different subunits
Difference between FO and F1
FO is membrane bound and F1 is projecting into matrix space
ATP synthase actions
Can generate and consume H+
ATP synthesis = H+ comes into matrix - rotor turns clockwise and then ADP phosphorylation to ATP
ATP hydrolysis = H+ comes out from matrix and rotor turns other way for dephosphorylation of ATP to ADP
Cathode (platinum)
Negatively charged - H+ ions are attracted to it so oxygen is reduced to form H2O
Silver anode
Negatively charged ; attracts Cl- so silver undergoes oxidation to form silver chloride
Oxygen electrode graph
ADP is added before decline and then oxidative phosphorylation occurs before O2 is finally exhausted
Metabolic poison - cyanide
Bind with high affinity to ferric iron in complex IV ; blocks flow of electrons and thus ATP production
Malonate
Competitive inhibitor of succinctness dehydrogenase (complex II) ; slows down flow of electrons from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate
Where does succinate dehydrogenase reside?
Inner mitochondrial membrane - passes electrons to ubiquinone via FAD
Dinitrophenol
Able to move protons through bilayers and thus chemically uncouples substrate oxidation from ATP production
Non shivering thermogenesis
UCP-1 (uncoupling protein) activated as a response to low body temp
ATP synthase is bypassed and much of energy in H+ gradient is dissipated as heat
Rotenone
Strong inhibitor of mitochondrial complex I
Oligomycin
Blocks proton channel (FO subunit)
Substrate level phosphorylation
Direct transfer of a phosphate group in glycolysis/TCA to form ATP or GTP
Delta G for NADH/FADH2 re-oxidation
NADH is -220 which is more than -167 for FADH2 ; so NADH re-oxidation can create more phosphoanhydride bonds (ATP delta G is -31)
ETC mobile carrier co-enzyme q
UBIQUINONE
FADH2 path
Succinate dehydrogenase (complex two) then goes on to co-enzyme q etc etc ; bypasses complex 1 so fewer membranes pumped into intermembrane space - so less ATP made when they flow back in via ATP synthase
NADH
Bypasses complex II
Where else is FADH2 created?
Glycerol-phosphate shuttle
Beta oxidation
If electrons were being transferred and there was no proton gradient
ENERGY WOULD BE DISSIPATED AS HEAT
To make ATP
Protons have to flow back via ATP synthase into matrix and this drives rotation of F1 region
To consume ATP
Reverse direction of proton flow
Base of chamber that houses the oxygen electrode
Teflon membrane which is permeable to oxygen ; underneath this is a platinum cathode and silver anode
Oxygen electrode
Small voltage of 0.6 volts causes oxygen defuses and reduced at platinum cathode to water
Electrolyte
Potassium chloride
With nothing being added to mitochondrial suspension
Gentle decline as oxygen is steadily consumed
When ADP is added
Oxygen uptake increases rapidly because ADP/inorganic phosphate control uptake of oxygen - this is called respiratory control ; matched oxygen consumption with actual energy requirements
Cyanide and Azide (N3-) bind to
Haem group in complex 4 blocking flow of electrons
Malonate
Closely resembles succinate so comp inhibitor of complex 2 ; slows down flow of electrons (from FADH2 originally) from succinate to ubiquinone by inhibiting oxidation of succinate to fumarate
DNP
Bypasses ATP synthase - transporting protons through bilayer and uncoupling ATP production from proton pumping
What does DNP lead to?
Weight loss - increased metabolic rate/body temp since more protons have to be pumped so more fuel must be metabolised to make ATP
DNP as a dieting agent
Doses are slight between death and dieting so do not use
Where is non-shivering thermogenesis seen?
Newborn babies/hibernating animals ; UCP-1 bypasses ATP synthase ; much of energy within proton gradient is dissipated as heat
Rotenone
Inhibits transfer from complex 1 to ubiquinone
Malonate
Inhibits complex 2 to ubiquinone
Cyanide and azide
Block final step of ETC
Oligomycin
Antibiotic binds to stalk of ATP synthase - blocking flow of electrons so blocking ATP synthesis
DNP
Proton IONOPHORE
Metabolism of succinate
Produces FADH2 which bypasses complex 1
