Cellular Respiration: Aerobic Respiration

Krebs Cycle Electron Transport Chain

and ATP Synthase

The Krebs Cycle• Occurs in the

mitochondria.• Produces high-

energy molecules (NADH and FADH2), CO2 and 1 ATP

• Also called the citric acid cycle

Step 1

• Pyruvic acid loses one carbon and two oxygen to form CO2 and Acetyl-CoA

• During this step high energy molecule of NADH is formed

Step 2

• Part of Acetyl-CoA combines with a 4-carbon compound to form citric acid

• During this step two high energy molecules are formed: one FADH2 and one NADH

Step 3

• Citric Acid loses one carbon and two oxygen to form CO2 and a 5-carbon compound

• During this step a high energy molecule of NADH is formed

Step 4

• The 5 carbon compound loses one carbon and two oxygen to form CO2 and a 4-carbon compound

• During this step one high energy molecule of NADH is formed and one ATP is formed

Overall Products of the Krebs Cycle

• How many CO2 are formed?

• How many NADH are formed?

• How many FADH2 are formed?

• How many ATP are formed?

Electron Transport Chain

• High energy electrons in NADH and FADH2 created during glycolysis and the Krebs cycle are used to pump H+ ions across the inner membrane of mitochondria to create a concentration gradient.

• Oxygen acts as a final electron acceptor combining with low energy electrons and H+ ions to form H2O

ATP Synthase

• The push of H+ ions flowing down their concentration gradient through an enzyme called ATP Synthase converts ADP into ATP ADP ATP

Total ATP formed from aerobic respiration from one molecule of glucose

• 2 ATP from glycolysis• 4 ATP from the 2 NADH

formed in glycolysis• 2 ATP from the Krebs

cycle• 24 ATP from the 8

NADH formed from the Krebs cycle

• 2 ATP from the 2 FADH2 formed from Krebs cycle