1. Module 4 Respiration
Glycolysis

2. Learning Objectives Success Criteria To understand Glycolysis
State that Glycolysis takes place in the cytoplasm
(Grade D)
State that during aerobi c respiration in animals pyruvate is actively pumped into mitochondria (Grade C)
Outline the process of Glycolysis (Grade B/A)

3. Evolutionary perspective
Prokaryotes
first cells had no organelles
Anaerobic atmosphere
life on Earth first evolved without free oxygen (O2) in atmosphere
energy had to be captured from organic molecules in absence of O2
Prokaryotes that evolved glycolysis are ancestors of all modern life
ALL cells still utilize glycolysis
The enzymes of glycolysis are very similar among all organisms. The genes that code for them are highly conserved.
They are a good measure for evolutionary studies. Compare eukaryotes, bacteria & archaea using glycolysis enzymes.
Bacteria = 3.5 billion years ago
glycolysis in cytosol = doesn’t require a membrane-bound organelle
O2 = 2.7 billion years ago
photosynthetic bacteria / proto-blue-green algae
Eukaryotes = 1.5 billion years ago
membrane-bound organelles!
Processes that all life/organisms share:
Protein synthesis
Glycolysis
DNA replication

4. Glycolysis - occurs in cytoplasm
Breaking down glucose
“Glyco – lysis” (splitting sugar)
Ancient pathway which harvests energy
where energy transfer first evolved
transfer energy from organic molecules to ATP
still is starting point for ALL cellular respiration
but it’s inefficient
generate only 2 ATP for every 1 glucose
glucose      pyruvate 2x 6C 3C
Why does it make sense that this happens in the cytosol?
Who evolved first?
That’s not enough ATP for me!

5. GLYCOLYSIS (carbohydrate splitting)
First stage of aerobic respiration & anaerobic respiration.
Doesn’t need O2 – so this stage is anaerobic!
Occurs in the cytoplasm of all living cells

7. Glycolysis - phosphorylation
The first stage actually begins by phosphorylating glucose to hexose 1,6-bisphosphate.
Each glucose uses 2 molecules of ATP

8. Glycolysis - phosphorylation
Glucose ATP ADP Glucose 6 phosphate Fructose 6 phosphate Fructose 1,6-bisphospahte

9. Glycolysis - lysis
This stage involves the breaking of the hexose bisphosphate into two triose phosphate molecules.
The triose phosphate is an intermediate in many biochemical reactions.
The phosphate group allows the sugar to form stronger interaction with the next enzyme in the pathway.

10. Glycolysis – oxidation/ATP formation
Each Triose phosphate is oxidised to a 3 carbon molecule called Pyruvate
Each Triose Phosphate has hydrogen removed (oxidation) to reduce one NAD+ to NADH + H+
Each Triose Phosphate adds a phosphate to ADP reducing this to ATP (substrate level phosphorylation)
Note that each Triose phosphate releases enough energy for the formation of two ATP

11. Summary of glycolysis
Glycolysis takes place in the cytoplasm of the cell.
It does not require oxygen.
The hexose sugar (glucose) is converted into two 3C atoms compounds called pyruvate.
Two ATP are consumed but four are produced making a net gain of 2 ATP
Two NADH + H+ are produced which will yield more ATP when they are transferred to the mitochondria and oxidative phosphorylation.
Yield: 2 Pyruvate + 2 ATP + 2NADH + 2H+

12. The first stage of respiration: glycolysis
Boardworks A2 Biology
Respiration

13. Glycolysis Why is Glycolysis termed anaerobic?
NAD+ + 2H  NADH + H+ (oxidised form ) (reduced form) NB Rather then write NADH, examiners often simply refer to it as reduced NAD or reduced coenzyme
Glycogen
You start with glycogen.
2 ATP
4 ADP + 4Pi
4 ATP
Triose -phosphate
(3C x 2)
Pyruvate
(3C x2)
Glucose
(6C)
2H x 2
NAD
Reduced NAD
2 ADP
Nicotinamide adenine dinucleotide = So it gains electrons
You finish with Pyruvate
Why is Glycolysis termed anaerobic?
What is the NET production of ATP?

14. The sums The end products of glycolysis are pyruvate and reduced NAD
Energy is released during this reaction.
4 molecules of ADP + Pi converted to 4 molecules of ATP.
So net gain of 2 molecules of ATP
2 pairs of hydrogen atoms produced
2 Molecules of pyruvate.

15. Products of Glycolysis
2 reduced NAD (NADH + H+)
2 Pyruvate
2 ATP

16. THIS DEPENDS ON THE AVAILABILITY OF OXYGEN!!!
The Fate of Pyruvate!
THIS DEPENDS ON THE AVAILABILITY OF OXYGEN!!!

17. Task
Complete exam questions (SA)

18. Plenary
Make list of what is needed for glycolysis and what is produced Explain where oxidation occurs and substrate level phosphorylation

19. Learning Objectives Success Criteria To understand Glycolysis
State that Glycolysis takes place in the cytoplasm
(Grade D)
State that during aerobi c respiration in animals pyruvate is actively pumped into mitochondria (Grade C)
Outline the process of Glycolysis (Grade B/A)