Intent to provide easy understanding to all subjects of METABOLISM & METABOLICS and GLYCOLYSIS Easy to understand short notes with illustrative diagrams to enhance quick understanding

1. GLYCOLYSIS
Glycolysis; Is a process of breaking down glucose. The
process yields two ATP molecules containing free energy,
two pyruvate molecules, two high energy, electron-
carrying molecules of NADH, and two molecules of
water.
OR
Is a process of releasing energy within sugars. In
Glycolysis a six carbon sugar (6C) mainly GLUCOSE, is
split into two molecules two molecules of three carbon
sugar (3C) called pyruvate.

2. The three (3) stages of Glycolysis.
1. Sugar phosphorylation.
This is the first stage in glycolysis, in this stage the
6C sugar is activated and making it more reactive.
ATP is used at this stage. Under this stage lie
several steps that are;

3. STEP 1.
Here, HEXOKINASE
enzyme adds a
phosphate group to the
Glucose in the cells
cytoplasm to form
glucose-6-phosphate.
One molecule of ATP is
consumed giving ADP.

4. STEP 2.
The ISOMARASE enzyme
PHOSPHOGLUCOISOMERA
SE isomerizes Glucose-6-
phosphate (G6P) into it’s
isomer Fructose-6-
phosphate (F6P)

5. STEP 3.
Then
PHOSPHOFRUCTOKINASE
uses another ATP
molecule to transfer a
Phosphate group to
Fructose-6-phosphate in
order to form Fructose-
1,6-bisphosphate. Two
ATP molecules used so
far.

6. STAGE TWO (2)
2. Lysis stage.
This is the second stage, whereof the phosphorylated six
carbon (6C) sugar is split into two molecules of three carbon
(3C) sugar which are isomers of each other.
This stage involves steps explained in next slides.

7. STEP 4.
The
enzyme aldolase splits
fructose 1,6-
bisphosphate into a
ketone and an aldehyde
molecule. These sugars,
dihydroxyacetone
phosphate (DHAP) and
glyceraldehyde 3-
phosphate (G3P), are
isomers of each other.

8. STEP 5.
• The enzyme triose-phosphate isomerase rapidly converts DHAP into
G3P (these isomers can inter-convert). G3P is the substrate needed
for the next step of glycolysis.

9. STEP 6.
The enzyme glyceraldehyde 3-
phosphate
dehydrogenase (GAPDH) serves
two functions in this reaction.
First, it dehydrogenates G3P by
transferring one of its hydrogen
(H⁺) molecules to the oxidizing
agent nicotinamide adenine
dinucleotide (NAD⁺) to form
NADH + H⁺.

10. Cont…
•Next, GAPDH adds a phosphate from the cytosol
to the oxidized G3P to form 1,3-
bisphosphoglycerate (BPG). Both molecules of
G3P produced in the previous step undergo this
process of dehydrogenation and
phosphorylation.

11. STEP 7.
The
enzyme phosphoglycero
kinase transfers a
phosphate from BPG to
a molecule of ADP to
form ATP. This happens
to each molecule of
BPG. This reaction yields
two 3-phosphoglycerate
(3 PGA) molecules and
two ATP molecules.

12. STEP 8.
The
enzyme phosphoglycer
omutase relocates the P
of the two 3 PGA
molecules from the
third to the second
carbon to form two 2-
phosphoglycerate (2
PGA) molecules.

13. STEP 9.
The
enzyme enolase removes
a molecule of water from
2-phosphoglycerate to
form
phosphoenolpyruvate
(PEP). This happens for
each molecule of 2 PGA
from step eight.

14. STEP 10.
The enzyme pyruvate
kinase transfers a P
from PEP to ADP to
form pyruvate and
ATP. This happens for
each molecule of PEP.
This reaction yields
two molecules of
pyruvate and two ATP
molecules.

15. INPUT, OUTPUT AND NET GAIN.
• Input in glycolysis are glucose molecules, 2NAD+ molecules
and 2ATP molecules.
• The output in the glycolysis are 4ATP molecules, 2pyruvate
molecules and 2NADH+
• The net gain of ATP is 2 ATP

16. The fate of pyruvate is OXYGEN dependent aerobic or anaerobic,
this depends on the presence or absence of oxygen.
1. In presence of OXYGEN (Aerobic), pyruvate is converted to
acetyl by the enzymes pyruvate dehydrogenase, then enters
the Krebs's cycle.
2. In absence of oxygen (anaerobic) conditions, pyruvate is
converted to lactate by the enzyme lactate dehydrogenase.
Pyruvate is also converted to acetaldehyde and furthermore
to ethanol.
FATE OF PYRUVATE