Tricarboxylic acid (TCA) cycle

functions of TCA cycle

• acceptor of acetyl-CoA produced from oxidation of fuel molecules

• generates electron carriers for the electron transport chain (ETC) to produce more ATP

acetyl-CoA

__ transports acetyl groups coming from fuel oxidation into TCA cycle

ETC

TCA cycle produces electron carriers used in the ___ to make 30-32 ATP molecules

acetyl-CoA production

pyruvate turned into acetyl-CoA via action of the pyruvate dehydrogenase complex 

• reaction NOT part of TCA cycle 

• preparatory step

• releases CO2

mitochondrial matrix

TCA cycle enzymes are located into the ____

cytoplasm

glycolysis and the pentose phosphate pathway both happen in the __ of the cell

pyruvate dehydrogenase complex

Connects glycolysis to the TCA cycle

• complex made of 3 enzymes: pyruvate dehydrogenase, dihydrolipoyl transacetylase, & dihydrolipoyl dehydrogenase

• reduces NAD to NADH

• very large protein complex

advantages of multienzyme complexes

• short distance between catalytic sites = channel substrate from one site to another

• Channeling of substrate = less side reactions

• regulation of activity of one enzyme/subunit affects the entire complex

PDHC deficiency

• Can be genetic, from cofactor deficiency (not enough thiamine pyrophosphate (TPP)), or due to poisoning/intoxication

• leads to lactic acidosis and neurological disturbance

citrate synthase

step 1: acetyl-CoA and oxaloacetate form citrate

• via ___ enzyme

• uses H2O

aconitase

step 2: citrate made into isocitrate using dehydration-rehydration reaction

• via ___ enzyme

• reaction moves forward by removal of isocitrate

isocitrate dehydrogenase

step3: isocitrate turned into alpha ketoglutarate

• via __ enzyme

• reduces NAD to NADH

• releases CO2

alpha-ketoglutarate dehydrogenase cpmplex

step4: alpha-ketoglutarate turned into succinyl-CoA

• via __

• requires acetyl-CoA

• requires TPP (thiamine pyrophosphate)

• releases CO2

• reduces NAD to NADH

succinyl-CoA synthetase

step 5: succinyl-CoA turned into succinate

• via ___ enzyme

• make GTP

• release acetyl-COA

nucleoside diphosphate kinase

If enough GTP and not enough ATP, GTP can be used to make ATP using the ___ enzyme and ADP.

succinate dehydrogenase

step6: succinate made into fumarate

• via ___ enzyme

• makes FADH2

fumarase

step7: fumarate made into L-malate

• via __ enzyme

• uses H2O

malate dehydrogenase

step 8: L-malate made into oxaloacetate

• via ___ enzyme

• reaction moved forward by removal of oxaloacetate

NADH

___ is produced by the following reactions:

• isocitrate to alpha-ketoglutarate

• alpha-ketoglutarate to succinyl-CoA

• malate to oxaloacetate

FADH2

__ is made by the reaction turning succinate into fumarate

GTP

__ is made by the reaction turning succinyl-CoA into succinate

6, 2, 2

TCA cycle product per glucose (aka 2 pyruvate thus 2 acetyl-CoA)

• __ NADH

• __ FADH2

• __ GTP

That is WITHOUT the acetyl-CoA production step!

anaplerotic reaction

reactions replenishing the intermediates of the TCA cycle as other pathways might use them