MODULE 12: Chapter 11.5 Flashcards
What regulates oxidative phosphorylation?
Cell’s need for ATP
This is indicated by the energy charge as a function of ATP, ADP, and AMP concentrations.
What happens to ADP levels when ATP is consumed at high rates?
ADP levels rise due to increased ATP hydrolysis.
Why is ADP a key control factor in oxidative phosphorylation?
It determines the rate of ATP synthesis and NADH oxidation.
What processes are activated by a low energy charge?
Citrate cycle and glycolysis.
What controls multiple steps in the citrate cycle?
Ratio of NADH to NAD⁺ in mitochondrial matrix.
What is required to maintain a high rate of oxidative phosphorylation?
Substrates for both the electron transport system and ATP synthesis.
What happens when ADP + Pi is added to a mitochondrial suspension lacking succinate?
O2 reduction and ATP synthesis increase only slightly.
What occurs when succinate is added to a mitochondrial suspension containing ADP + Pi?
Rates of O2 reduction and ATP synthesis increase dramatically.
What is the effect of cyanide on the electron transport system?
It blocks the flow of electrons through complex IV.
What happens to O2 consumption after cyanide is added?
The rate of O2 consumption decreases rapidly.
What is the result of adding oligomycin to a mitochondrial suspension?
Inhibits ATP synthesis and decreases O2 consumption.
What role does 2,4-dinitrophenol play in oxidative phosphorylation?
It acts as a chemical uncoupler, stimulating O2 consumption.
What is the consequence of 2,4-dinitrophenol on energy production?
Energy is wasted as heat.
Why was 2,4-dinitrophenol banned as a human consumer product?
It is poisonous and can lead to serious health issues.
What types of inhibitors disrupt oxidative phosphorylation?
- Direct inhibitors of ATP synthase (e.g., oligomycin)
- Inhibitors of electron transport (e.g., cyanide, azide)
- Chemical uncouplers (e.g., 2,4-dinitrophenol)
- Inhibitors of ATP/ADP translocase (e.g., atractyloside)
What is uncoupling protein 1 (UCP1) also called?
Thermogenin.
Where is UCP1 highly expressed?
In brown adipose tissue.
What is the primary function of UCP1?
To control thermogenesis by uncoupling electron transport from ATP synthesis.
What is the difference between brown and white adipose tissues?
- Brown adipose tissue has many mitochondria and smaller fat droplets
- White adipose tissue has large fat droplets and fewer mitochondria
What is nonshivering thermogenesis?
Heat production without muscle contraction.
What is Leber hereditary optic neuropathy (LHON) caused by?
Defects in complex I and complex III proteins.
Which cells are most affected by mitochondrial diseases?
Neuronal cells and skeletal muscle.
What is H–ubiquinone?
An oxidoreductase involved in the electron transport system.
Which complexes are associated with mitochondrial diseases?
Complexes I, III, and IV of the electron transport system.
