Lecture 3 Flashcards
Explain the key role of pyruvate dehydrogenase in glucose metabolism.
Pyruvate dehydrogenase is a key site of regulation into the TCA cycle.
The enzyme is involved in the production of acetyl CoA which is used in the TCA cycle.
The reaction is irreversible and is hence regulatory.
Describe the roles of the tricarboxylic acid cycle (TCA cycle) in metabolism.
Takes place in the Mitochondria.
Acetyl is converted to 2CO2
The cycle is oxidative and so required NAD+, FAD
Some energy produced as ATP/ GTP
Lots of precursors/ intermediates for biosynthesis are produced.
Harvests high energy electrons.
Explain how the TCA cycle is regulated.
The cycle is regulated by energy availability. i.e. ATP/ADP ration and NADPH/NAD^+ ratio.
Different stages are regulated by enzymes and by the extent of the activation of those enzymes.
Describe the key features of oxidative phosphorylation.
Electrons are transferred from NADH and FAD2H to molecular oxygen.
The energy released is used to generate a proton gradient (proton motive force (pmf)).
Energy from the dissipation of the proton motive force is coupled to the synthesis of ATP from ADP.
Regulation of oxidative phosphorylation.
When ATP is high and so ADP is low there is no substrate for ATP synthase (the enzyme involved in the production of ATP) so no ATP is synthesised this stops the inward flow of H+ into the mitochondrial matrix this increases the concentration of H+ in the intramitochondrial space and so further H+ translocation stops and hence electron transport.
Explain the processes of electron transport and ATP synthesis and how they are coupled.
Electrons are transferred through series of carrier molecules to O2 with the release of energy (about 30% of the energy goes to move the e- across the inner mitochondrial membrane the rest is lost as heat).
ATP is synthesized by adding a phosphate group to ADP.
The energy released from electrons transferred is used top create a proton gradient (pmf).
The energy from the dissipation of the proton motive force is coupled to the synthesis of ATP from ADP.
Describe how, when and why uncoupling of these processes occur in some tissues.
Uncouplers increase the permeability of the mitochondrial inner membrane to protons.
this dissipates the proton gradient and hence reducing the pmf by providing an alternate return for the protons to return to the matrix. Producing heat.
Brown adipose tissue uses this to keep warm.
