Carbohydrate & Krebs & ETC Flashcards
Explain the role of pyruvate dehydrogenase in glucose metabolism
Pyruvate transported across mitochondrial membrane then enzyme converts pyruvate to acetyl CoA – IRREVERSIBLE = key regulatory step – requires cofactors, can be allosterically regulated (high energy = off)
What happens when there is PDH deficiency?
Won’t pass pyruvate to the TCA = build up, need to replenish NAD+ = LDH activity increases = pyruvate to lactate = lactate acidosis
Briefly what is the TCA cycle?
Introducing a acetyl-CoA 2C + 4C = citrate 6C
recover reducing equivalents NADH FADH2,
prod GTP by substrate level phosphorylation,
release C from acetyl CoA as CO2,
Isomerisation,
Oxidative steps
Prod precursors for biosynthesis
NEEDS O2
How many TCA cycles from every glucose entering glycolysis?
2
What does TCA stand for?
Tricarboxylic acid cycle
What is the role of the TCA cycle in metabolism?
Removal of reducing power
Explain how the TCA cycle is regulated
enzymes catalysing reactions are allosterically regulated, isocitrate oxidised to alpha-ketoglutarate = irreversible = key regulatory step that removes reducing power, where CO2 is reduced = irreversible
What is oxidative phosphorylation?
oxidative phosphorylation is when ATP is generated from the oxidation of NADH/FADH2 and subsequent transfer of electrons and pumping of protons e.g. ETC
The TCA cycle supplies the biosynthesis of what?
Fatty acids, AA, Haem, glucose
Why will the TCA cycle not function in the absence of O2?
Prod a lot of NADH and FADH if no oxidation this pathway will stop
With regards to permeability what is the structure of the mitochondria?
Porous outer membrane, then intermembrane space, inner impermeable membrane contains the matrix
What is the role of oxidative phosphorylation in energy production?
To generate ATP from the oxidation of NADH/FADH2
Explain the process of the ETC
NADH passes the captured electrons to a ‘proton translocating complex’ in the inner mitochondrial membrane, as this occurs the electrons give up a little bit of energy to pass 2H+ through the inner mitochondrial membrane to the intermembrane space – the electrons are then passed to PTC2 with removal of 2H+ and then PTC3 with removal of 2H+ - finally the electrons are picked up by O + 2H+ to form H2O = creating a H+ gradient
What is the H+ gradient in the mitochondria also known as?
Proton motive force (pmf)
How is ATP produced in the ETC?
ATP synthase = uses the pmf – takes 2H+ back into the matrix which subsequently = ADP + P ATP
How can oxidative phosphorylation be inhibited?
Cyanide binds haem very strongly = prevents acceptance of e- by O2 in the final ETC – reducing the creation of pmf.
Stops transport of e- and ATP prod
Describe how, when and why uncoupling of oxidative phosphorylation occurs in some tissues
Whole process is dependent on the permeability of mitochondria – increase permeability = dissipates the pmf and stops ATP prod e.g. dinitrophenol, fatty acids
Uncoupling can occur in brown adipose tissue – stops electron transport but produces heat (babies, hibernating animals)
What is substrate level phosphorylation?
Substrate level phosphorylation is directly phosphorylating ADP with a phosphate and energy is provided from a coupled reaction e.g. in the krebs cycle and glycolysis
Compare substrate level phosphorylation and oxidative phosphorylation
Substrate level phosphorylation
directly phosphorylating ADP with a phosphate and energy is provided from a coupled reaction – can occur in absence of O2,
oxidative phosphorylation
ATP is generated from the oxidation of NADH/FADH2 and subsequent transfer of electrons and pumping of protons – cannot occur in absence of O2
Overall what is the net production of ATP?
32
A lot of energy is lost in ATP production as?
heat
