Reactions of glycolysis

1. BIOCHEMISTRY
metabolism
Glycolysis
(bright sakaika)

2. objectives
By the end of this presentation you should be able to :
1. Define metabolism and its types
2. Define glycolysis
3. Describe and illustrate glycolysis pathway
4. Amount of ATP produced in glycolysis
5. Importance of glycolysis

3. Introduction
• Metabolism is a process where living organisms acquire and utilize (make use
of) energy for various body functions.
• Types
• Anabolism : involves the synthesis of complex molecules from
simpler molecules (energy is used) e.g synthesis of
glycogen from glucose
• Catabolism : is the breakdown of complex molecules to their
constituents (energy is produced) e.g food digestion

4. Glycolysis
• Glycolysis is a series of metabolic processes that metabolize glucose molecule into two
pyruvate molecules.
• Occurs in cytosol of the cell.
• it takes 10 steps of enzymatic reactions to degrade one molecule of glucose into two
pyruvates.
• Glucose is a 6-carbon molecule while pyruvate is made up of 3 carbon atoms

5. Glycolysis cont…
• High energy molecules are produced in glycolysis these are
i. ATP (adenosine triphosphate)
ii. NADH ( reduced nicotinamide adenine dinucleotide)

6. Stepsofglycolysis
The following is a series of reactions that take place in glycolysis

7. Step 1: phosphorylation of
glucose
• An enzyme hexokinase catalyzes the
phosphorylation of glucose to form
glucose-6-phoshate
• ATP is utilized forming ADP

8. Step 2: isomerization of G6P
• Glucose-6-phosphate is
isomerized to fructose-6-
phosphate by an enzyme
phosphoglucose isomerase

9. Step 3: phosphorylation of FBP
• Fructose-6phosphate gets phosphorylated to
form fructose-1,6-phosphate.
• This reaction is catalyzed by an enzyme
phosphofructokinase
• ATP is utilized and ADP is produced

10. Step 4: cleavage of
FBP
• A six carbon compound FBP
splits into two 3-carbon
compounds GAP and DHAP
by the help of an enzyme
adolase

11. Step 5:
isomerization
• Triose phosphate isomerase
catalyzes the isomerization of DHAP to
GAP.
• Only GAP can proceed in the
glycolysis so a ketose DHAP is
converted to an aldose GAP.

12. Note:
We started with one glucose molecule (6-carbon molecule)
In reaction 5 two trioses (3-carbon molecules) are
produced and each GAP molecule proceeds in a different
path
Two ATPs have been used

13. Lets now look at reactions that will produce energy

14. Step 6: oxidation of
GAP
• GAP gets oxidized by NAD+ and Pi
forming 1,3-bisphophoglycerate
• This reaction is catalyzed by
glyceraldehyde-3-phosphate
dehydrogenase
• NADH is produced by reducing
NAD+

15. Step 7: First ATP synthesis
• 1,3-BPG gets dephosphorylated to
form 3-phosphoglycerate
• ATP is produced

16. Rxn 8:
phosphoglycerate
Mutase
• Phosphoryl group of 3GP is
tranferred to a second
carbon forming 2-
phosphoglycerate.
• This reaction is catalyzed by
phosphoglycerate mutase

17. Rxn 9: dehydration
of 2GP
• Enolase catalyzes the
dehydration of 2-
phosphoglycerate to
phosphoenolpyruvate

18. Rxn 10: second ATP synthesis
• Pyruvate kinase catalyzes the
formation of pyruvate from
phosphoenolpyruvate.
• ATP is produced.

19. ATP
• From reaction 6, energy starts to be produced
1 NADH
2 ATP
• Remember from stage 5, 2GAP were produced and each one goes into a different
reaction
• Therefore at the end of each reaction we produced one pyruvate molecule and one
NADH and two ATPs
• Combining both reactions we have 2 pyruvates, 2 NADH and 4 ATPs

20. ATP cont..
• Recall we used 2 ATP molecules and produced 4
• So the overall ATP = 2
• 1 NADH = 2.5 ATP
• Therefore at the end we have
2 ATP + (2 × 2.5) ATP
= 2 + 5
= 7 ATP

21. Importance of glycolysis
• Production of energy
• It is quick
disadvantage
oHowever the energy produced is minimal

22. •Thank you
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