1. Respiration Things to cover: Structure and the mitochondria
What happens in:
Glycolysis (already done)
Link reaction
Krebs cycle
Oxidative phosphorylation (next lesson)

2. Learning Objectives Success Criteria
Produce accurate notes on the link reaction
Summarise in a diagram the key events in the Krebs cycle
Carry out an experiment and analyse the results to demonstrate the role of coenzymes in respiration
Describe what the link reaction is
Describe what happens during the Krebs cycle
Explain the role of hydrogen carrier molecules in the Krebs cycle

3. Quick 5 (they start easy and get harder)
Formula of Glucose
Name of the first stage of aerobic respiration
This can be divided into two phases; name them
The energy released by respiration is used in which condensation reaction
Name the Enzyme that catalyses this reaction

4. Review of last week’s learning
Complete the Glycolysis gaps task.
Easier – Ask me for a clue
Harder –Turn it over and draw it out on the back
Extension:
More Pi is used to generate ATP in the energy pay off phase than is added onto the substrate by the hydrolysis of ATP – where does the extra Pi come from?
The process of ATP formation in glycolysis is described as being by “substrate level phosphorylation” – suggest what this means

5. Glycolysis with gaps (level 2) Glucose (6 Carbon) __________
Fructose-6-phosphate
Hexose___________
( ___ carbon)
2 x Triose Phosphate (________)
2x intermediate compounds (3 carbon)
2x Pyruvate (3 carbon)
2 ADP +2 Pi
2ATP

6. Glycolysis steps Glucose (6 Carbon) Glucose-6-phosphate (6 carbon)
Fructose-6-phosphate
Hexose1,6-bisphospahe
2 x Triose Phosphate (3 carbon)
2x intermediate compounds (3 carbon)
2x Pyruvate (3 carbon)
ATP
ADP
ATP
ADP
2 x
2 x
Oxidased NAD
Reduced NAD
2 x
2 x
ATP + Pi
ATP
2 x
2 x
ATP + Pi
ATP

7. Glycolysis releases less than 25% of the chemical energy stored in Glucose.
Where is the energy originally from?
Where is the energy that is left

8. Tricarboxylic acid cycle

9. Respiration Part 2
The Link Reaction

10. Mitochondria

11. Glycolysis forms Pyruvate in the cytoplasm
Glycolysis forms Pyruvate in the cytoplasm. Pyruvate is a polar molecule.
The link reaction takes place in the mitochondrial matrix
Which structures would you expect to find in the membranes of the mitochondrial envelope and why ?

12. Link Reaction Basics
Connects Glycolysis to Krebs cycle (Respiration part 3)
Takes place in the mitochondrial matrix
Requires presence of oxygen (but does not use oxygen)
Overview:
Pyruvate is decarboxylated – a Carboxyl group is removed and forms CO2.
2Hydrogen are removed from Pyruvate and used to reduce NAD
Produces Acetate (2 carbon molecule) that binds to Coenzyme A.

13. Link Reaction Start Pyruvate (3 carbon compound) Step1
Pyruvate decarboxylase removes a carboxyl group
Formed =CO2
Step 2
Pyruvate dehydrogenase removes hydrogen atoms from the pyruvate
Hydrogen atoms are accepted by NAD+ which is reduced to NADH
Formed = NADH + Acetate (2 carbon compound)

14. Step 3
Coenzyme A (CoA) accepts the Acetate to form Acetyl Coenzyme A
This carries acetate into the Krebs cycle
2 Pyruvate + 2NAD++ 2CoA  2CO2+2NADH+2acetyl CoA Why is there two of everything? What is being oxidised, what is being reduced?

15. Krebs cycle Takes place in the mitochondrial matrix
Each step is enzyme controlled
Does not require oxygen but can not take place if oxygen is not present therefore it is an aerobic process
Respiratory substrates other than glucose can enter aerobic respiration at the beginning of the krebs cycle:
Fatty acids – broken down to acetates enter via CoA
Amino Acids – deaminated and changed to Acetate or pyruvate

16. Krebs cycle is:
Oxidation of Acetate (from the link reaction) to Carbon dioixde
Produces per acetate:
2 molecules of CO2
1 molecule of ATP (by substrate level phosphorylation)
3 NADH (Reduces 3 molecules of NAD+)
1 FADH (Reduces 1 molecule FAD+)

17. Step 1a:
Coenzyme A releases the Acetate group
Acetate (2 carbon compound) is joined to Oxaloacetate (4 carbon compound)
Makes a 6 carbon compound called Citrate (6 carbon)

18. Step 1b:
The citrate (6 carbon) is then shuffled using the enzyme aconitase to form Isocitrate (6 carbon)
This means that oxidative decarboxylation (the next step) can take place

19. Step 2a: Decarboxylation of isocitrate
Carboxyl group removed form isocitrate
Produces:
1x CO2
1 x 5 carbon compound (α-Ketoglutarate)

20. Step 2b: Oxidation of isocitrate
Dehydrogenation of isocitrate molecule
Hydrogen atoms removed by dehydrogenase enzymes
Hydrogen accepted by NAD+ which is reduced
Produces 1 x NADH

21. Step 3a: α-Ketoglutarate (5 carbon) is oxidised to Succinyl (4 carbon)
Decarboxylation of α-Ketoglutarate (5 carbon)
Produces:
1x CO2
1 x 4 carbon compound (Succinyl)

22. Step 3b: α-Ketoglutarate (5 carbon) is oxidised to Succinyl (4 carbon)
Dehydrogenation of Ketogluterate
Hydrogen atoms removed by dehydrogenase enzymes
Hydrogen accepted by NAD+ which is reduced
Produces 1 x NADH

23. Step 4: Succinyl converted to Succinate (4 carbon compound).
Succinyl (4 carbon compound) is converted to Succinate (4 carbon compound).
The energy released by this step is directly used in a condensation reaction to form ATP from ADP
This is substrate level phosphorylation
Produces
1x ATP

24. Step 5: Succinate (4 carbon compound) oxidised to Fumerate (4 carbon compound).
Dehydrogenation of Succinate
Hydrogen atoms removed by dehydrogenase enzymes
Hydrogen accepted by FAD+ which is reduced
Produces 1 x FADH

25. Step 5b: The secret step
Fumerate (4 carbon compound) converted to Malate (4 carbon compound)

26. Step 6: Malate (4 carbon compound) oxidised to Oxaloacetate (4 carbon compound).
Dehydrogenation of Malate (4 carbon compound)
Hydrogen atoms removed by dehydrogenase enzymes
Hydrogen accepted by NAD+ which is reduced
Produces 1 x NADH
(Oxaloacetate used in step 1 is regenerated – ready to accept another acetate)

27. The Products of the Link Reaction go to the Krebs Cycle and the ETC
So for each glucose molecule:
2 acetyl coenzyme A (go into the Krebs cycle)
2 Carbon dioxide (released as a waste products)
2 Reduced NAD (go to the electron transport chain)

28. Krebs Cycle II
Use the animation to further annotate your H/W from last lesson

29. Tricarboxylic acid cycle

30. The Krebs Cycle Acetyl Coenzyme A (2C) NAD Coenzyme A 2C Reduced NAD
Oxaloacetate (4C)
Citrate (6C)
(6C)
(4C)
NAD
(4C)
CO2
FAD
Reduced
NAD
Reduced
FAD
CO2
(5C)
(4C)
NAD
ADP + Pi
ATP
(4C)
Reduced
NAD

31. DeNa DeNa A Fa... Na
This little tune will help you to remember the Krebs Cycle.
Remember, respiration is all about releasing energy from your food.
Oxidation releases energy.
When a carbon compound is oxidised, coenzymes are reduced.
The coenzymes involved are: NAD and FAD.
Decarboxylation is the removal of CO2.
Remember this: 665 and five 4’s.

32. DENA DENA A FA... NA
DENA: Decarboxylation and production of reduced NAD
A: Production of ATP
FA... : Production of reduced FAD (The ‘...’ means a gap)
NA: Production of reduced NAD

33. The Krebs Cycle: DENA DENA A FA... NA
Acetyl Coenzyme A (2C)
NAD
Coenzyme A 2C NA
Reduced
NAD
Oxaloacetate (4C)
Citrate (6C)
(6C)
(4C)
NAD
(4C)
DENA
CO2
FAD
Reduced
NAD FA
Reduced
FAD
CO2
(5C)
(4C)
DENA
NAD
ADP + Pi
ATP A
(4C)
Reduced
NAD

34. Krebs Cycle Summary 2 CO2 molecules 1 ATP molecules (S.L.P)
Each Acetyl CoA entering the cycle results in:
2 CO2 molecules
1 ATP molecules (S.L.P)
4 pairs of H atoms (Later used in the E.T.C to produce ATP)
Used to reduce NAD and FAD. Three reduced NAD are produced and 1 reduced FAD per cycle.
NAD = Nicotinamide adenine dinucleotide
FAD = Flavine adenine dinucleotide

35. Krebs Cycle Summary 2 CO2 molecules 1 ATP molecules (S.L.P)
Each Acetyl CoA entering the cycle results in:
2 CO2 molecules
1 ATP molecules (S.L.P)
4 pairs of H atoms (Later used in the E.T.C to produce ATP)
Used to reduce NAD and FAD. Three reduced NAD are produced and 1 reduced FAD per cycle.
NAD = Nicotinamide adenine dinucleotide
FAD = Flavine adenine dinucleotide

36. How many times does the Krebs cycle “turn” for each molecule of glucose that enters respiration? Give a reason for your answer.
What are the products of the Link reaction and Krebs cycle for one molecule of glucose
Suggest which genes may be found on a mitochondria contain a DNA plasmid.

37. Tasks P55 text book read the text and answer the questions
Exam Questions

38. Glycolysis

39. Krebs Cycle