the krebs cycle Flashcards
what is the krebs cycle
a series of biochemical steps that lead to the complete oxidation of glucose, resulting in carbon dioxide, water and quite large amounts of ATP
how are steps of the krebs cycle controlled
they are controlled and catalysed by specific intracellular enzymes
where do the krebs cycle steps take place
in the matrix of the mitochondrion
where is ATP produced in the krebs cycle
-produced in the stalked particles on the inner mitochondrial membranes in the presence of oxygen
the link reaction
reaction that links glycolysis to the krebs cycle
step 1 of the link reaction
the 3C pyruvate crosses into the mitochondria through the mitochondrial membrane from the cytoplasm
step 2 of the link reaction
-an atom of carbon is removed from pyruvate resulting in formation of carbon dioxide molecule and 2C joins with coenzyme A to form 2C acetyl coenzyme A
decarboxylation
when at atom of carbon is removed from pyruvate
what also happens when acetyl CoA is formed
pyruvate is oxidised losing hydrogens to NAD resulting in reduced NADH
dehydrogenation
pyruvate oxidised losing hydrogens to NAD
step 3 of the link reaction
reduced NAD used later in electron transport chain to produce ATP
-energy contained in acetyl CoA released in the krebs cycle
decarboxylases
enzymes that remove carbon dioxide
dehydrogenases
enzymes that remove hydrogen
equation for link reaction
pyruvate (3C) + CoA + NAD = acetyl CoA(2C) + CO2+ reduced NAD( NADH)
what do all reduced hydrogen acceptors do
channel hydrogen through the electron transport chain to produce ATP
1 stage of krebs cycle
-2C acetyl CoA combined with 4C compound to form 6C compound citric acid (citrate)
-at this point it has entered krebs cycle
step 2 of krebs cycle
-6C citric acid goes through cyclical series of reactions and compound if broken down to give original 4C compound
-2 molecules of Co2 removed in process and given off as waste product
step 3 of krebs cycle
-4C compound then combines with more 2C acetyl CoA and cycle begins again
what enters for every molecule of pyruvate that enters krebs cycle
-three molecules of reduced NAD (NADH), one of reduced FAD and one of ATP are produced
-the NADH and FAD enter electron transport chain
for each molecule of glucose that enters the glycolytic pathway what else enters
-the krebs cycle turns twice because the 6C glucose produced two 3C pyruvate molecules- each of which pass through krebs cycle
