link reaction

why does link reaction need to occur

• end product of glycolysis is pyruvate

• pyruvate contains a substantial amount of chemical energy that can be used to produce more ATP

• when oxygen is available pyruvate will enter the mitochondrial matrix and aerobic respiration will continue

• pyruvate moves across the double membrane of the mitochondria via ACTIVE TRANSPORT

  • it requires a transport protein and a small amount of ATP

how does pyruvate enter the mitochondrial matrix

• from the cytoplasm by active transport

• link reaction= links glycolysis and Krebs cycle

what happens during link reaction

• pyruvate 3C is converted to acetate 2C/ acetyl coenzyme A

• CO2 is removed

• also produces some reduced NAD

where does the link reaction happen

• link occurs in the mitochondrial matrix

• pyruvate is actively transported across the outer and inner mitochondrial membranes and into the mitochondrial matrix

another name for link reaction

• oxidative decarboxylation

• decarboxylation refers to the fact it removes carbon and oxygen from each pyruvate molecule

stage 1 decarboxylation

• co2 is removed from pyruvate, changing it from a 3C molecule to a 2C

• this is done by pyruvate decarboxylase

• co2 then diffuses out of mitochondria

stage 2 oxidation/dehydrogenation

• pyruvate dehydrogenase then removes hydrogen from pyruvate

• this is accepted by NAD to from NADH

• this then leaves acetate instead of pyruvate

stage 3: bonding

• reaming 2C of acetate combines with coenzyme A to produce acetyl coenzyme A (acetyl coA)

• this delivers the acetyl group into the krebs cycle

reactants of link reaction

• 1 x pyruvate

• 1 x NAD

• 1 x Coenzyme A

products of link reaction

• 1 x acetyl coA

• 1 x reduced NAD

• co2

NO ATP PRODUCED

how many link reactions per glucose molecule

• 2 reactions per glucose molecule

word equation of link reaction

2 pyruvate ( 2 molecules of pyruvate from each molecule of glucose) + 2 NAD + 2 CoA—- 2 CO2 + 2NADH + 2 acetyl CoA

what is the 2 NADH released used in

• reduced NAD used to synthesize ATP in oxidative phosphorylation

• used in the electron transport chain

important to remember when asked to describe a single glucose molecule

• multiply everything by 2