Glycolysis-Krebs PDF

Cellular Respiration Cellular respiration is a series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body. Cellular respiration includes both aerobic and anaerobic respiration but is often...

Cellular Respiration Cellular respiration is a series of chemical reactions that break down glucose to produce ATP, which may be used as energy to power many reactions throughout the body. Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat) The Stages of Cellular Respiration: A Preview Harvesting of energy from glucose has three stages – Glycolysis (breaks down glucose into two molecules of pyruvate) – The citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate Glycolysis occurs in the cytoplasm and has two major phases – Energy investment phase – Energy payoff phase Glycolysis occurs whether or not O2 is present Cellular respiration starts with glycolysis, which has two main phases: 1. Glycolysis I / Energy Investment Phase: uses ATP 2. Glycolysis II / Energy Payoff Phase: produces ATP molecules and pyruvate Oxidation of Pyruvate to Acetyl CoA Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle This step is carried out by a multienzyme complex that catalyzes three reactions  The citric acid cycle, also called the Krebs cycle, completes the break down of pyruvate to CO2 For one glucose molecules, there will be two rounds of Krebs cycle. This is because two molecules of Pyruvic acid are formed from one molecule of glucose during Glycolysis. The cycle generates 1 ATP, 3 NADH, and 1 FADH2 per turn The TCA Cycle Step 1: Acetyl CoA (two-carbon molecule) joins with oxaloacetate (a 4-carbon molecule) to form citrate (a 6-carbon molecule). Step 2: Citrate is converted to isocitrate (an isomer of citrate) Step 3: Isocitrate is oxidized to alpha-ketoglutarate (a five-carbon molecule) which results in the release of carbon dioxide. One NADH molecule is formed. Step 4: Alpha-ketoglutarate is oxidized to form a 4-carbon molecule. This binds to coenzyme A, forming succinyl CoA. A second molecule of NADH is produced, alongside a second molecule of carbon dioxide. Step 5: Succinyl CoA is then converted to succinate (4-carbon molecule) and one GTP/ATP molecule is produced. Step 6: Succinate is converted into fumarate (4-carbon molecule) and a molecule of FADH₂ is produced. Step 7: Fumarate is converted to malate (another 4-carbon molecule). Step 8: Malate is then converted into oxaloacetate. The third molecule of NADH is also produced. Products (1 turn) 1 ATP 3 NADH 1 FADH2 2 CO2