Biochem Lect 18-19 Flashcards
what are the two possible fates for pyruvate
it will either become lactate where lactate dehydrogenase reduces it by redox reaction in aneorobic reaction
or pyruvate can continue t become acetyl-CoA and that will require oxygen and mitocondria
how does pyruvate from glycolysis in cytoplasm get to mitochondria for citric acid cycle
by the pyruvate dehydrogenase complex which connects glycolysis and TCA cycle as it si large complex with 3 differenyt subunits and need 5 cofactors for catalysis: three ate prosthetic groups= thoamine pyrophosphate(TPP), lipoamide, and FAD
the rest two are coenzyme= coenzyme A and NAD+
how is pyruvate dehydrogenase complex reaction favourable
this reaction is oxidizing pyruvae and activtaing it, but thid id redox decraboxylation as it gives CO2 and NADH
the large negative delta G means it is facourable anf irreversible
what are the 5 steps reaction of PDC complex
each of the 3 subunits will catalyze different reactions but all 3 linked as they are coupled to each other, each subunit will do as its name
E1= decarboxylation as it is pyruvate dehydrogenase
E2= redox reaction as it is dihydrolipoyl transacetylase
E3= redoz reaction as it is dihydrolipoyl dehydrogenase
what is end product of PDC complex and how PDC complex regulated
end product is acetyl CoA from pyruvate
two ratios will regulate PDC: ATP/ADP or ATP/AMP and NADH/NAD+
high ATP and NADH inhibit PDC cycle
how is PDC controlled by feedback inhivition
also known as product inhibition
when acetyl CoA is high, that causes inhibition of E2
when NADH is high, that will inhibit E3
how is PDC regulated by covalent modification
PDC can also be phosphorylated
if it is phorphorylated by PD kinase, that inactivates the E1 complex which turns the whole complex off
if it is dephosphorylated by PD phosphatatse, that will activate E1 and turn on the complex
how is PDC complex allosterically regulated
by acetyl CoA, NADH, pyruvate, ADP and Calcium can also stimulate PD phosphotase and restore PDC activity
why is acetyl CoA an important and useful moelcule
because all different metabolic fuels can generate acetyl CoA, such as fatty acids, ketone bodym sugars, pyruvatem and ethanol
so it is the center for enrgy metabolism
what is general role of TCA cycle and how is it unique from glycolysis and PDC complex
this cycle is oxidizing fuel one, meaning it links breakdown of fuel molecule to ATP production in oxidative phosphorylation
it is the second phase of respiration where ATP geenration come from oxidative phosphorylation while breakdown of metabolite, such a glycolysis pathway, and PDC are first phase of respiration where it is oxidizing fuel
what is net reaction of 1 round of citric acid cycle
acetyl CoA+Pi+GDP+2H2O+3NAD++1FAD–> 3H++2CO2+3NADH+1FADH2+GTP+CoA
where does CO2 carbons originate
from oxaloacetate
which TCA intermediate can be made from amino acid
by transamination reaction, can make alpha-ketoglutamate from glutamate and oxaloactetae from aspartate
how is isocitrate converted to alpha-ketoglutarate in the TCA cycle
by enzyme isocitrate dehydrogenase and byproducts of this reaction are CO2 and protons
what is overview of TCA cycle
stage 1= known as oxidative decarboxylation where acetyl CoA, which is 2C molecule, combine with oxaloacetate, a 4C molecule, and form citrate which is 6C molecule and this starts TCA cycle
where the 2Cs are oxidized to CO2 and generate oxaloacetate in process
stage 2= regenerate oxaloacetate
this si where GTP is made by substrate level phosphorylatrion and 2 H2O molecules are needed by reactions
4 pairs of electrons are also used to reduce and form 3 NADH and 1FADH2 for oxidative phosphorylation
succinate dehydrogenase is membrane bound protein linking TCA cycle to oxidative phosphorylation
