Week 3 Flashcards
What is ATP?
Adenosine triphosphate
What do we get when we split ATP and move the terminal phosphate with hydrolysis?
Release of energy and ADP
What makes the hydrolysis of ATP energetically favourable?
- Relieves electrostatic repulsion between phosphate groups
- increased entropy
- the released phosphate ion is resonance stabilised
What is enthalpy?
- Chemical bond energy symbol H
- the enthalpy change is the sum of the energy used to break bonds and the energy released when new bonds are formed (triange H sign)
What is gibbs free energy change?
determines whether a reaction can take place considering both enthalpy and entropy changes. Δ G = Δ H − T Δ S
What determines the direction of a reversible reaction in the cell?
The value of ΔG and hence the direction of the reaction depends on concentrations of reactants and products
How can an energetically unfavourable reaction be achieved in the cell?
By coupling it to a favourable one. often to hydrolysis of ATP
What is OILRIG
Oxidation is loss (of electrons)
Reduction is gain
What is a redox carrier?
The reactions of the electron transport chain are redox reactions
What do spontaneous reactions look like?
Spontaneous reactions proceed downhill to create products with lower free energy than reactants
What are the 3 stages of cellular respiration?
1- Production of acetyl-CoA
2- Oxidation of acetyl CoA
3- Electron transport and chemiosmosis
What are flavoproteins?
Flavin nucleotide can accept either 1e- or 2e-
What is ubiquinone?
Coenzyme Q10. Electron carrier not bound to a protein complex. Freely diffusible in the non-polar interior of the IMM
What are cytochromes?
c1, c, a, a3.
Capable of absorbing visible light due to haem groups
What is NADH dehydrogenase?
Oxidises NADH from the TCA cycle, fatty-acid oxidation and glycolysis
- Reduces ubiquinone for the rest of the respiratory chain
- transports protons across inner mitochondrial membrane to support ATP synthesis
What does chemiosmotic coupling do?
Generates a proton motive force
What does chemiosmotic coupling do?
Generates a proton motive force
What is the rotary catalysis model in mitochondria?
in the ‘‘open state’’, ADP and phosphate enter the active site.
- the protein then closes up around the molecules and binds them loosely
- the enzyme then undergoes another change in shape and forces these molecules together, with the active site in the resulting tight state binding the newly produced ATP molecule with very high affinity
What are the causes of mitochondrial dysfunction?
- Impairment of electron transport and ATP-synthesis machinery -single enzyme disorder
- Inadequate number of mitochondria- impaired mitochondrial dynamics/biogenesis
- accumulation of damaged mitochondria- impaired mitophagy
What is a single enzyme disorder in mitochondria dysfunction?
Disruption of a single enzyme disrupts the energy production by the mitochondria
What is an example of a single enzyme disorder?
Complex 1 disorders.
range of symptoms and severity
50% fatal under 2 years
-mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes
What is heteroplasmy?
- Presence of <1 type of mitochondrial genome
- multiple copies of mtDNA per cell and not segregated like nuclear genome
What happens in mitochondrial fission?
- Cytosolic dynamin-related protein is phosphorylated
- Drp1 recruited to mitochondria and binds receptors
- Forms cuff around mitochondrion which constricts the organelle
- constriction severs both membranes
- generates new mitochondria
Explain mitochondrial fusion
Mitofusin 1 and 2 localise to the outer membranes and dock the two mitochondria together, fusing the outer membrane
- Optic atropy localised on the inner membrane, responsible for fusing the two inner membranes together
- sharing contents of mitochondria diltues any effect of damage
