citric acid cycle Flashcards
glycolysis process
glucose –> 2pyruvate
lactate is a product of
aerobic respiration
the citric acid cycle occurs during
aerobic respiration and is responsible for the generation of ATP and NADH and FADH
citric acid cycle is also known
kreb or TCA cycle tricarboxylic acid
the citric acid produces ….e- for oxidative phosphorylation
8 electrons -used to pump 36H+ across the mitochondrial inner membrane into the mitochondria space –> produces 9atp via ATP synthase
the citric acid cycle is an important course of precursors
-storage form of rules -bulding blocks of amino acids -building blocks of nucleotide bases -cholesterol, heme
occurs in the
mitochondrial matrix
purpose of TCA
to harvest high energy electrons from carbon rules and generate NADH and FADH2
what are the 2 carbon units that arrive to be oxidised
acetyl CoA
mitochondria
..
formation of Acetyl CoA
pyruvate +CoA +NAD+ –> acetyl CoA + CO2 +NADH
by product of the link reaction
carbon dioxide
which enzyme catalyses pyruvate to acetyl co A
pyruvate dehydrogenase complex
a specific carrier transports oyrivate into the
mitochondria from the cytoplasm (where glycolysis occurs)
during the link reaction pyruvate is
oxidatively decarboxylated t acetyl CoA -by pyruvate dehydoregnase
the link reaction is..
irreversible -loss of carbon is irreversible
pyruvate dehydrogenase
multi-enzyme complex giant -4-10 million daltons -can be seen using an electron microscope
chemical link reaction via pyruvate (pic)
- first pyruvate is decarboxylates and CO2 is released. then the complex is oxidised and loses 2 e-. Now the complex carries a positive charge and this means that CoA can be transferred –> acetyl CoA
pic of the citric acid cycle
pic
order of the citric acid cycle starting from when acetyl CoA joins oxaloacetate clare is knitting saskia some fleeces mostly orange
citrate isocitrare ketoglutarate succinyl CoA succinate Fumarate malate oxaloacetate
order of citric acid cycle
citrate isocitrate ketogluatarge succinyl coA succinate fumarate malate oxaloacetate
Oxaloacetate + acetyl CoA
-citrate synthase -adol condensation reaction followed by hydrolysis -citrylCoA and citrate
adol condensation reaction followed by hydrolysis with citrate synthase
ocaloacetate + acetyl CoA –> Citryl CoA + citrate
citrate loses water to form
cis-aconitate (intermediate) gains water to form isocitrate -both step of the reaction are catalysed by ACONITASE
aconitase
-an iron-sulfur protein -one of the iron atoms binds to the citrate -the iron facilitates the dehydration/hydration reactions
isocitrate –> NAD+ is reduced to form a NADH +H+
produces oxalosuccinate, then it is protonated and CO2 is lost producing ketoglutarate -isocitrate dehydrogenase
alpha ketoglutarate
key step in the production of nADH NAD+ and CoA joins ketoglutarate and Succinyl CoA is formed as well as CO2 and NADH
succinyl CoA joins with
Pi and GDP to form Succinate and CoA + GTP succinyl CoA synthetase
Succinate to fumarate
succinate dehydrogenase -key step in production of FADH
Fumarate to malate
fumarase
malate to oxaloacetate
malate dehydrogenase -key step in production of nADH
how is TCA regulated
concentration fo ATP and NADH
key control points are
-isocitrate dehydrogenase -alpha ketoglutatrta dehydrogenase
other control points
-pyruvate dehydrogenase irreversible loss of C) -isocitatrate dehydrogenase- inhibited by ATP and NADH -Ketoglutarate dehydrogenase- inhabited by ATP, succinyl CoA and NADH
isocitrate dehydrogenase
inhibited by ATP and NADH
ketoglutarate dehydrogenase
inhabited by ATP, succinyl CoA and nADH
overall picture of the citric acid cycle
Acetyl CoA + 3NAD+ + FAD +GDP +Pi –> 2CO2 + 3NADH + FADH2 + GTP +CoA
during the citric acid cycle there is still not a lot of
ATP or GTP generated
product yields
2 molecules of CO2 GTP 3NADH (6 electrons) FADH (2 electrons)
3NADH
6 electrons
FADH
2 electrons
summary of TCA
-generates NADH and FADH2 -utilised by ETC -together, the citric acid cycle and the electrons transport chain provides >95% of the energy used by aerobic cells -also generates vital metabolic precursors
pathways linked to the citric acid cycle
pic
arsenic inhibits the Citric acid cycle
arsenic and mercury inbits pyrvate dehydrogenase complex by inactivating the dihydrolipomide component of the transacetylase -leads to central nervous system pathologies
which enzyme is inhabited by arsenic and mercury
inhibits pyruvate dehydrogenase complex by inactivating the dihydrolipomide component of the transacetylase.
mad as a hatter
the strange behaviour of hat makers who sued mercury nitrate
lewisite
arsenic based chemical weapon in WW2 BAL (british anti-lewisite) was used as an antidote
