Molecular Fundamentals - Krebs Cycle

what can’t directly go to the Krebs cycle?

pyruvate

CoA has a large affinity for what?

carbons

what describes the transitional step before the Krebs Cycle?

pyruvate is converted to acetyl CoA by pyruvate dehydrogenase

what converts pyruvate to acetyl CoA so it can enter the Krebs Cycle?

pyruvate dehydrogenase with NADH and CoA-SH

where does the Krebs cycle take place?

in the mitochondria

what is the function of the Krebs cycle?

to produce ATP

acetyl CoA combines with oxaloacetate to form what?

citrate

what enzyme works to combine acetyl CoA with oxaloacetate to form citrate?

citrate synthase

what enzyme works convert citrate to isocitrate?

aconitase

conitase converts citrate into what?

isocitrate

what enzyme converts isocitrate to α-Ketoglutarate?

isocitrate dehydrogenase with NAD⁺

what are the products of isocitrate converting to α-Ketoglutarate via isocitrate dehydrogenase?

NADH and CO₂

what describes the process of oxidative decarboxylation?

removing carbon to produce CO₂

isocitrate is converted to what by isocitrate dehydrogenase?

α-Ketoglutarate

what enzyme converts α-Ketoglutarate to succinyl CoA?

α-Ketoglutarate dehydrogenase with NAD⁺

α-Ketoglutarate is converted to what by α-Ketoglutarate dehydrogenase?

succinyl CoA

what two steps are considered oxidative decarboxylation?

• isocitrate converting α-Ketoglutarate via isocitrate dehydrogenase 

• α-Ketoglutarate converting to succinyl CoA via α-Ketoglutarate dehydrogenase

what are the products of α-Ketoglutarate converting to succinyl CoA via α-Ketoglutarate dehydrogenase?

NADH and CO₂

succinyl CoA is converted to what by succinyl coA synthetase ?

succinate

what enzymes converts succinyl CoA to succinate?

succinyl CoA synthetase with GDP

succinyl CoA converting to succinate via succinyl CoA synthetase uses what to do what?

GDP → GTP → ADP → ATP (the formation of GTP → ADP removes CoA from succinyl CoA)

succinate is converted to what by succinyl dehydrogenase?

fumarate

what enzymes converts succinate to fumarate?

succinyl dehydrogenase with FAD

the process of succinate converting to fumarate via succinyl dehydrogenase involves what?

FAD converting to FADH₂

why is FAD/FADH₂ process used over NAD⁺/NADH process?

FAD removes 2 H⁺ at the same time while NAD⁺ only removes 1 H⁺ at a time

what enzyme converts fumarate to malate?

fumarase with the addition of H₂O

fumarase converts fumarate to what?

malate

what enzymes converts malate to oxaloacetate?

malate dehydrogenase with the NAD⁺

malatate is converted to what via malate dehydrogenase and NAD⁺?

oxaloacetate

what inhibits citrate synthase?

ATP, NADH, or succinyl CoA

what activates citrate synthase?

ADP

what inhibits aconitase?

rat poison (fluoroacetate)

what inhibits isocitrate dehydrogenase?

ATP

what activates isocitrate dehydrogenase?

ADP, Ca²⁺

what activates α-Ketoglutarate dehydrogenase?

Ca²⁺

what inhibits α-Ketoglutarate dehydrogenase?

NADH, succinyl CoA

one pyruvate molecule yields what after going through Krebs cyclet?

• 2 CO₂

• 3 NADH

• 1 FADH₂

• 1 ATP

citrate is used to form what?

fatty acids

α-Ketoglutarate is used for what?

amino acid synthesis and neurotransmitters

succinyl CoA is needed for what?

heme synthesis

malate is needed for what?

gluconeogenesis

oxaloacetate is needed for what?

amino acid synthesis

beriberi disease is what?

a deficiency of thiamin (B1)

what enzymes require thiamin (B1)?

pyruvate dehydrogenase and α-Ketoglutarate dehydrogenase

dry beriberi is when what is involved?

CNS

• evidence of symmetric peripheral neuropathy with motor and sensory changes

  • dimished reflexes

wet beriberi is when what is involved?

cardiovascular system 

• impaired myocardial energy metabolism and dysautonomia

• dilated cardiomyopathy

• tachycardia

• high-output congestive heart failure

• peripheral edema

arsenic can inhibit what enzymes therefore inhibiting the Krebs cycle?

pyruvate dehydrogenase and α-Ketoglutarate dehydrogenase

what are symptoms of arsenic poisoning?

• memory loss and other neurological conditions such as Parkinson disease

• apoptosis of cerebral neurons

• brain DNA damage leading to brain cell death