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6.2

6.2. Radjewski AP Biology. Cellular Respiration. Catabolism (break down) of organic molecules within cells Key ways cells get energy 4 steps Glycolysis Formation of Acetyl CoA ( pyruvate oxidation) Krebs Cycle (Acetyl CoA oxidation) Electron Transport/ Chemiosmosis

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6.2

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  1. 6.2 Radjewski AP Biology

  2. Cellular Respiration • Catabolism (break down) of organic molecules within cells • Key ways cells get energy • 4 steps • Glycolysis • Formation of Acetyl CoA (pyruvate oxidation) • Krebs Cycle (Acetyl CoA oxidation) • Electron Transport/Chemiosmosis • Occurs in a bunch of small steps to allow for more energy to be made

  3. Glycolysis • Takes place in the cytosol in the cytoplasm • All organisms have cytoplasm, so all organisms can do glycolysis • 10 steps • Glucose is oxidized releasing stored energy • To break down glucose, cells need to invest 2 ATP’s (endergonic)

  4. ATP is required because glucose has covalent bonds, which are strong. The phosphate from the ATP’s are basically being added to glucose in these steps.

  5. The 6 carbon molecule is broken in half, creating two 3C sugars.

  6. Later steps are exergonic and release energy, forming ATP and NADH. ATP is made through substrate level phosphorylation

  7. Glycolysis Ins/Outs • Requirements: 1 glucose, 2 ATP, 2 NAD+,4 ADP, 4 Pi • Products: 2 Pyruvates, 4 ATP,2 NADH, 2 ADP, 2 Pi • Net ATP Production is 2ATP • In the presence of oxygen, further oxidation can occur.

  8. Formation of Acetyl CoA (Pyruvate Oxidation) • Takes place in the mitochondria matrix • Pyruvate gets oxidized to a 2C acetate molecule and CO2 • Then Acetate is bound to Coenzyme A (CoA), forming acetyl coenzyme A or Acetyl CoA • It is a carrier of acetyl groups • Vitamin B • Exergonic reaction (released NADH) and decarboxylation occurred (release of CO2)

  9. Formation of Acetyl CoA (Pyruvate Oxidation) • Requirements: pyruvate, NAD+, Coenzyme A • Products: Acetyl CoA, NADH, CO2 • The main role of Acetyl CoA is to donate its acetyl group to the 4C compound oxaloacetate, forming a 6C compound, citrate

  10. Krebs Cycle • Citric Acid Cycle • 8 steps • 2C Acetyl CoA combines with 4C oxaloacetate to form 6C citrate • Citrate changes to its isomer isocitrate in step 2 (water was added and released) • In step 3, isocitrate undergoes decarboxylation to form 5C alpha-ketoglutarate. • This releases CO2 and forms NADH

  11. Krebs Cycle • In step 4, alpha ketoglutarate undergoes decarboxylation to form 4C succinyl CoA • NADH is formed and CO2 is released • In step 5, succinyl CoA loses it’s CoA to form succinate • This is a coupled reaction where GDP + Pi forms GTP, which then transfer its high energy phosphate to form ATP

  12. Krebs Cycle • In step 6, succinate undergoes dehydrogenation to form fumarate • This forms FADH2, which is similar to NADH • In step 7, fumarate adds water forming malate • In step 8, malate undergoes dehydrogenation forming oxaloacetic acid (which started the cycle!) • NADH was made!

  13. Krebs Cycle • Requirements: Acetyl CoA, 3 NAD+, 1 GDP, 1Pi, FAD, Water, CoA, Oxaloacetate • Products: 3 NADH, Water, 2 CO2, 1 ATP, FADH2 • So far, we only made 3 ATP (2 from glycolysis, and 1 from Krebs) This isn’t a lot. How do we make all the energy?

  14. Electron Transport Chain • Occurs on the cristae of the mitochondria • NADH and FADH2 are oxidized and it is exergonic • The protons get pumped through proton channels on the cristae and go through chemiosmosis • Remember this creates a proton gradient and then they go back through ATP synthase, driving the reaction to create ATP from ADP and Pi • The electrons pass through proteins and then add to oxygen (with protons)

  15. Oxidative Phosphorylation

  16. Oxidative Phosphorylation • Requirements: NADH, FADH2, Oxygen • Products: Yields a lot of ATP and H20 • For each NADH or FADH2, 2-3 ATP molecules are formed

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