1. Starter For some light relief..although biologically correct!!
Remember????
Remind yourself!

2. Glycolysis: True or False
Glycolysis produces a net gain of 4 ATP molecules
The co-enzyme NADH is oxidised during glycolysis
When coenzymes become reduced, they carry hydrogen molecules
Glycolysis takes place in the matrix of the mitochondrion
In glycolysis, glucose is converted in this order: glucose, triose phosphate, hexose bisphosphate then pyruvate
If you think they are false, you must write the correct version- and there are false ones!!!

3. Glycolysis produces a net gain of 4 ATP molecules- False: the net gain is 2 ATPs as 2 are used up
The co-enzyme NADH is oxidised during glycolysis- False: NAD is reduced during glycolysis to form NADH
When coenzymes become reduced, they carry hydrogen molecules- False: they carry hydrogen atoms, not molecules or ions
Glycolysis takes place in the matrix of the mitochondrion- False: it takes place in the cytoplasm
In glycolysis, glucose is converted in this order: glucose, triose phosphate, hexose bisphosphate then pyruvate- False: the correct order is glucose, hexose bisphosphate, triose phosphate, pyruvate

4. Cellular Respiration

5. The Start of the Krebs Cycle
Some History first…
The Krebs Cycle (also known as the Tricarboxylic Acid cycle – TCA cycle for short) is named after Sir Hans Krebs, a German – British scientist who pieced together the 8 series of reactions.

6. Glycolysis releases less than a quarter of the chemical energy stored in glucose, most of the energy remains stocked in the two molecules of pyruvate.
Pyruvate is the starting block for the Krebs Cycle

7. The Start of the Krebs Cycle
If oxygen is present, the pyruvate enters the mitochondrial matrix (via a transport protein), where the enzymes of the Krebs cycle complete the oxidation of the organic fuel
Cytosol
Mitochondria O- C O
Pyruvate
Transport Protein C O
CH3
What type of respiration will be occurring in this example?
AEROBIC RESPIRATION

8. The Link Reaction learning outcomes
State that the link reaction takes place in the mitochondrial matrix;
Outline the link reaction, with reference to decarboxylation of pyruvate to acetate and the reduction of NAD;
Explain that acetate is combined with coenzyme A to be carried to the next stage;

9. The Link Reaction The link reaction happens when oxygen is available…
For each glucose molecule used in glycolysis, two pyruvate molecules are made
But the link reaction uses only one pyruvate molecule, so the link reaction and the Krebs cycle happen twice for every glucose molecule which goes through glycolysis
The link reaction happens in the matrix of the mitochondrion

10. The function is to carry the acetate into the Krebs cycle
Pyruvate 3C
Decarboxylation- removal of a carboxyl group (which becomes CO2) by the enzyme pyruvate decarboxylase 1C
CO2
Dehydrogenation- the enzyme pyruvate dehydrogenase removes hydrogen atoms from pyruvate and NAD accepts it 2C
acetate
NAD
Coenzyme A
(CoA)
Accepts the 2C acetate
NADH 2C
Acetyl CoA
The function is to carry the acetate into the Krebs cycle

11. Tasks Summarise the link reaction
State the products of the link reaction for each glucose molecule

12. The Products of the Link Reaction go to the Krebs Cycle
So for each glucose molecule:
Two molecules of acetyl co enzyme A go into the Krebs cycle
Two carbon dioxide molecules are released as a waste product of respiration (decarboxylation)
Two molecules of reduced NAD are formed and go into the electron transport chain (dehydrogenation)

13. Exam Questions
Describe what happens in the link reaction (4)

14. Answers
The 3-carbon pyruvate is combined with coenzyme A (1) to form a 2-carbon molecule, acetyl coenzyme A (1). The extra carbon is released as carbon dioxide (decarboxylation of pyruvate) (1). The coenzyme NAD is converted into reduced NAD in this reaction by accepting hydrogen ions (dehydrogenation of pyruvate)

15. The Challenge: Whiteboards
Can you draw glycolysis and the link reaction….?