AEROBIC RESPIRATION – THE FOUR STAGES
1. GLYCOLYSIS - occurs in the cytoplasm.
• Two ATP is hydrolysed into 2 ADP AND 2 Pi.
• Glucose is phosphorylated and made more reactive.
• Then hydrolysed into two triose phosphate molecules.
• Each triose phosphate is oxidised and loses hydrogen each to NAD.
• NAD gains the hydrogen and becomes two reduced NAD.
• Two ATP molecules are regenerated back.
• Each triose phosphate molecule converts into two pyruvates.
Therefore, the end products are:
• 2 ATP
• 2 Pyruvates
• 2 reduced NAD.
2. LINK REACTION – occurs in the matrix of the mitochondria.
• The two pyruvate molecules produced during glycolysis are actively
transported into the mitochondria’s matrix.
• Each pyruvate molecule loses one carbon dioxide and one hydrogen.
• Forms two molecules of (2 carbon) acetates.
• NAD gains the hydrogen molecule to become a reduced NAD.
• Each acetate combines with a coenzyme A to produce a compound
called Acetyl coenzyme A.
The overall equation:
• Pyruvate + NAD + Co A = Acetyl CoA + reduced NAD + CO₂
3. KREBS CYCLE – occurs also in the matrix of the mitochondria.
• The Acetyl CoA (2 carbon) from the link reaction links with a four-carbon
molecule (oxaloacetate) to form a six-carbon molecule (citric acid).
• The citric acid is oxidised as it loses hydrogen to NAD.
• NAD gains the hydrogen and becomes reduced NAD.
• 3 NAD for each pyruvate, so three reduced NAD.
• The citric acid also loses 2 CO₂ to form a four-carbon molecule.
• The four-carbon molecule loses hydrogen to FAD.
• FAD gains the hydrogen and forms a reduced FAD.
• ATP is produced, then the process repeats again.
1. GLYCOLYSIS - occurs in the cytoplasm.
• Two ATP is hydrolysed into 2 ADP AND 2 Pi.
• Glucose is phosphorylated and made more reactive.
• Then hydrolysed into two triose phosphate molecules.
• Each triose phosphate is oxidised and loses hydrogen each to NAD.
• NAD gains the hydrogen and becomes two reduced NAD.
• Two ATP molecules are regenerated back.
• Each triose phosphate molecule converts into two pyruvates.
Therefore, the end products are:
• 2 ATP
• 2 Pyruvates
• 2 reduced NAD.
2. LINK REACTION – occurs in the matrix of the mitochondria.
• The two pyruvate molecules produced during glycolysis are actively
transported into the mitochondria’s matrix.
• Each pyruvate molecule loses one carbon dioxide and one hydrogen.
• Forms two molecules of (2 carbon) acetates.
• NAD gains the hydrogen molecule to become a reduced NAD.
• Each acetate combines with a coenzyme A to produce a compound
called Acetyl coenzyme A.
The overall equation:
• Pyruvate + NAD + Co A = Acetyl CoA + reduced NAD + CO₂
3. KREBS CYCLE – occurs also in the matrix of the mitochondria.
• The Acetyl CoA (2 carbon) from the link reaction links with a four-carbon
molecule (oxaloacetate) to form a six-carbon molecule (citric acid).
• The citric acid is oxidised as it loses hydrogen to NAD.
• NAD gains the hydrogen and becomes reduced NAD.
• 3 NAD for each pyruvate, so three reduced NAD.
• The citric acid also loses 2 CO₂ to form a four-carbon molecule.
• The four-carbon molecule loses hydrogen to FAD.
• FAD gains the hydrogen and forms a reduced FAD.
• ATP is produced, then the process repeats again.
