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Glycolysis

Glycolysis. Chapter 2.1. What’s the point?. The point is to make ATP !. ATP. Glycolysis. There are 2 main phases of glycolysis : Glycolysis I - activation phase, which uses ATP molecules

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Glycolysis

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  1. Glycolysis Chapter 2.1

  2. What’s thepoint? The pointis to makeATP! ATP

  3. Glycolysis • There are 2 main phases of glycolysis: Glycolysis I - activation phase, which uses ATP molecules • Glycolysis II - oxidative and phosphorylation reactions, which not only reduce glucose to pyruvate but also produce ATP molecules • C6H12O6 + 2ADP + 2Pi + 2 NAD+ -----> 2 pyruvate + 2ATP + 2(NADH + H+)

  4. Stage 1: Glycolysis • Occurs in cytoplasm • Anaerobic and does not require oxygen • Glucose is split into two 3-C molecules called pyruvate (pyruvic acid). • Transfers only 2.2% of free energy available in 1 mol of glucose to ATP.

  5. Glycolysis • Each step of the glycolytic pathway requires the use of a specific enzyme • This process occurs in the cytoplasm of the cell and does not require oxygen • Thus it is a part of anaerobic respiration

  6. Step 1 • The first step of glycolysis is “energy-requiring”. This energy is made available when an ATP molecule donates a phosphate group to glucose (G6P) in a phosphorylation reaction • The main products of this reaction are glucose-6-phosphate (G6P) and ADP

  7. Steps 2 & 3 Step 2: • The glucose-6-phosphate is converted to fructose-6-phosphate (F6P) Step 3 • A second ATP is used to transfer a phosphate group to the sugar • Now the molecule fructose -1,6-biphosphate (F1,6BP)

  8. Steps 4 & 5 • The backbone splits apart to form 3-carbon molecules of glyceraldehyde-3-phosphate (G3P) • One comes from a temporary DHAP molecule

  9. Step 6 • Each molecule of NAD+ reacts with a molecule of G3P • In this rxn, electrons (e- ) and protons (H+ ) are gained by NAD+ converting it to NADH (thus 2 NADH are formed) • Since NADH gained electrons (and hydrogen), it has been reduced

  10. Step 6 contd • Since G3P lost electrons (and hydrogen), it has been oxidized • As well, each G3P gains a phosphate group which was floating around the cytoplasm • This produces 2 molecules of 1,3-biphosphoglycerate (BPG)

  11. Step 7 • Each molecule of BPG donates a phosphate group to an ADP molecule producing 2 molecules of ATP • Such a transfer from a glycolysis intermediate to ADP is called substrate-level phosphorylation. • This step of glycolysis is energy releasing since ATP was made • This leaves 2 molecules of 3-phosphoglycerate (3PG)

  12. Steps 8 & 9 Step 8: • Each 3PG is converted into 2-phosphoglycerate (2PG) Step 9: • Each 2PG releases a water molecule leaving 2 molecules of phosphoendpyruvate (PEP)

  13. Step 10 - YAY • Each PEP performs a substrate level phosphorylation by donating a phosphate group to an ADP producing 2 more ATP • This leaves two 3-carbon molecules of pyruvate Net products of Glycolysis: • 2 ATP (2 in, 4 out) • 2 NADH • 2 pyruvate

  14. Glycolysis: From Glucose to Pyruvate • O is not a strong enough oxidizer to strip electrons from C-H bonds in glucose at room or body temperature. Enzymes required. • Glycolysis is a pathway of ten enzyme-catalyzed reactions located in the cytoplasm. It provides starting materials for both cellular respiration and fermentation.

  15. Glycolysis – Energy In ATP phosphorylates glucose Rearrangement Stick on another phosphate (phosphorylation)

  16. Split (F1,6BP) into two things, most important one G3P Take 2nd thing and rearrange into G3P too! Add a phosphate to get some NADH Take off phosphate and put it on ADP (-- ATP) Rearrange to get phosphate in diff place

  17. Steal some H2O to convert from 2PG to PEP • Take that last phosphate off and the process makes ATP

  18. GLYCOLYSISPRODUCTS 2 ATPs are used in steps 1 & 3 to prepare glucose for splitting. F 1,6-BP splits into DHAP and G3P. DHAP converts to G3P. 2 NADH are formed in step 6. 2 ATP are formed by substrate-level phosphorylation in both steps 7 and 10. 2 pyruvatesare produced in step 10.

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