Glycolysis is the first stage of respiration, where glucose is broken down into two pyruvate molecules. It occurs in two steps: first, glucose is phosphorylated using ATP to form glucose-6-phosphate; second, the glucose-6-phosphate is oxidized to form two pyruvate molecules, producing a net gain of two ATP molecules. The pyruvate molecules then enter the mitochondria for the link reaction, where they are converted into two acetyl CoA molecules to enter the Krebs cycle, with carbon dioxide and NADH also produced.

1. Glycolysis

2. The first stage of respiration Glycolysis

3. Respiration Process of respiration is split into four parts By breaking it into four parts we will have less to learn at any one stage

4. Glycolysis is the first stage of respiration!

5. Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate

6. Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule

7. Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule Pyruvate is a triose (3-carbon) molecule

8. Glycolysis is the first stage of respiration! Glycolysis splits one molecule of glucose into two smaller molecules of pyruvate Glucose is a hexose (6-carbon) molecule Pyruvate is a triose (3-carbon) molecule Pyruvate is also known as pyruvic acid

10. Glycolysis takes place in the cytoplasm of cells.

11. Glycolysis takes place in the cytoplasm of cells.

12. It’s the first stage of both aerobic and anaerobic respiration.

13. It’s the first stage of both aerobic and anaerobic respiration. It doesn’t need oxygen to take place – so it’s anaerobic

14. It’s the first stage of both aerobic and anaerobic respiration. It doesn’t need oxygen to take place – so it’s anaerobic

15. There are TWO STAGES of GLYCOLYSIS – Phosphorylation and Oxidation

16. Glycolysis

17. Glycolysis 1 2 A B

18. Glycolysis 1 2 A B These arrows in diagrams just mean that A goes into the main reaction and is converted to B. A will normally release or collect something from molecule 1, e.g. hydrogen or phosphate

19. Stage One - Phosphorylation

20. Stage One - Phosphorylation Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate.

21. Stage One - Phosphorylation Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. The hexose phosphate is split using water

22. Stage One - Phosphorylation Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. The hexose phosphate is split using water ( hydrolysis )

23. Stage One - Phosphorylation Glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP to give a hexose phosphate. The hexose phosphate is split using water ( hydrolysis ) 2 molecules of triose phosphate and 2 molecules of ADP are created.

24. A triose phosphate is just a simple 3-carbon sugar with a phosphate group attached. Different books use different names!

25. What’s the point? Glucose can now no longer leave the cell.

26. What’s the point? Glucose can now no longer leave the cell. Molecules produced are much more reactive!

27. Stage Two - Oxidation

28. Stage Two - Oxidation The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate .

29. Stage Two - Oxidation The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate . Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD ( NADH + H + )

30. Stage Two - Oxidation The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate . Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD ( NADH + H + ) A coenzyme is a helper molecule that carries chemical groups or ions, e.g. NAD + removes H + and carries it to other molecules.

31. Stage Two - Oxidation The triose phosphates are oxidised (lose oxygen), forming two molecules of pyruvate . Coenzyme NAD + collects the hydrogen ions, forming 2 reduced NAD ( NADH + H + ) 4 ATP are produced, but 2 were used up at the beginning, so there’s a net gain of 2 ATP .

32. Next in Aerobic respiration….

33. Next in Aerobic respiration…. The 2 molecules of reduced NAD go to the electron transport chain (ETC), part 4 of respiration.

34. Next in Aerobic respiration…. The 2 molecules of reduced NAD go to the electron transport chain (ETC), part 4 of respiration. 2. The two pyruvate molecules go into the matrix of the mitochondria for the link reaction .

35. I bet your so excited you can not wait!

36. The Link Reaction

37. The Link Reaction The second stage of respiration

39. You are now in the matrix of the mitochondria!

41. Link Reaction – 2 nd stage of respiration

42. Link Reaction – 2 nd stage of respiration The Link Reaction converts Pyruvate to Acetyl Coenzyme A

43. Link Reaction – 2 nd stage of respiration The Link Reaction converts Pyruvate to Acetyl Coenzyme A The link reaction happens when oxygen is available.

44. Link Reaction – 2 nd stage of respiration

45. Link Reaction – 2 nd stage of respiration One carbon atom is removed from pyruvate in the form of CO 2 .

46. Link Reaction – 2 nd stage of respiration One carbon atom is removed from pyruvate in the form of CO 2 . The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A ( acetyl CoA ).

47. Link Reaction – 2 nd stage of respiration One carbon atom is removed from pyruvate in the form of CO 2 . The remaining 2-carbon molecule combines with coenzyme A to produce acetyl coenzyme A ( acetyl CoA ). Another oxidation reaction happens when NAD + collects more hydrogen ions . This forms reduced NAD ( NADH + H + ).

48. Link Reaction – 2 nd stage of respiration 4. No ATP is produced in this reaction.

49. Link Reaction – 2 nd stage of respiration The Link reaction happens Twice for every Glucose Molecule

50. Link Reaction – 2 nd stage of respiration The Link reaction happens Twice for every Glucose Molecule So for every glucose molecule used in glycolysis, two pyruvate and two acetyl CoA molecules are made.

51. So for each glucose molecule:

52. So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration)

53. So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration)

54. So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration

55. So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)

56. So for each glucose molecule: Two molecules of acetyl CoA go into Krebs cycle (part 3 of respiration) Two carbon dioxide molecules are released as a waste product of respiration Two molecules of reduced NAD are formed and go into the electron transport chain (part 4 of respiration)

57. Final thoughts…. Acetyl Co-what????? It IS very confusing, but you need to know it. Take your time and fet to grips with one stage at a time. Don’t worry if you can not remember all the details straight away. If you can remember where each stage starts and what the products are, you’re getting there!