A.B.
Two phases of Glycolysis
Glycolysis
ANAEROBIC PROCESS
To start off, what does Glycolysis mean?
Break it down, yo!
Glyco + lysis
(sugar) (to split apart)
In short, in this process we are splitting apart
a glucose molecule
Glucose is a six carbon molecule, however
in the process of glycolysis, this glucose will
be split apart into two molecules of
pyruvate.
Glucose: C-C-C-C-C-C
Pyruvate: C-C-C
(basta we’re breaking this 6-carbon
molecule into half, sO EASY, but that’s
only the basic concept of glyco)
In this process, some of the energy released
as glucose converse into 2 pyruvates is
captured in the form of ATP and NADH.
First Phase: Investment Phase, consumes
energy (steps 1-5)
Second Phase: Pay Off Phase, produces
energy (steps 6 - 10)
1st Phase
In the idea of investment, we have to buy or
give first in order that you can sell for more
later.
In glycolysis, you need to put in energy so
that you could produce more energy latur!
The first phase of glycolysis is an
endothermic process (ENDO - absorbing
energy; EXO - releasing energy)
In this phase, you need to put two molecules
of ATP to get the process started.
2nd Phase
In this phase, we’re going to produce energy
but a lot more energy than the energy you
put in.
Net Reaction of Glycolysis
Glycolysis occurs in the cytosol of the cell.
Starting with a glucose molecule reacts with
2 NAD+ molecules and 2 ADP units with 2
inorganic phosphate ions, producing 2
molecules of pyruvate and 2 molecules of
NADH plus 2 hydrogen ions will form and 2
ATP molecules will be produced.
- Glucose + 2NAD+ + 2ADP + 2Pi
→ 2 Pyruvate + 2NADH + 2H+ +
2ATP + 2H20
So after the 2nd phase, you’ll get 4
molecules of ATP with 2 molecules of
NADH.
IN SUMMARY, the net gain is two
molecules of ATP and two molecules of
NADH. (two molecules na lang ng ATP kasi
-2 from the two ATP’s we used during the
process)
A.B.
the fact that the acceptor molecule is glucose
containing 6 carbons.
EQUATION: Glucose + ATP → Glucose6-phosphate + ADP
10 Steps of Glycolysis
Step 1: Phosphorylation of Glucose
to G6P
ADDITIONAL:
We need Magnesium^2+ ions in order for
this process to work. (Mg^2+)
Step 2: Isomerization
Glucose
(C6H12O6)
G-6-P
G6P
So where does the phosphate come from?
- From the ATP molecule, converted to
ADP.
SO THERE’S AN ENZYME that transfers
the phosphate from the atp to the glucose
acceptor molecule (G6P), it’s called the
hexokinase enzyme.
A kinase enzyme catalyzes the transfer of a
phosphate group from atp to another
acceptor molecule. Hexo, means six, due to
Fructose - 6 - phosphate
What’s the relationship between the glucose
6 phosphate and fructose 6 phosphate?
- Both still have phosphate groups but what
changed is it went from glucose to fructose
(they’re isomers of each other)
In this process, we use phosphohexose
isomerase enzyme.
A.B.
With a phosphate group attached to the 6carbon so that’s why it’s called …
Step 4: Cleavage of fructose 1,6
bisphosphate
EQUATION: Glucose-6-phosphate →
Fructose-6-phosphate
Step 3: Phosphorylation of F-6-P to
F-1,6-BP
F-1,6-BP
F - 6- P
Notice 2 molecules, a ketone (C=O) and an
aldehyde (O=C-H). A 3-carbon aldehyde is
known as glyceraldehyde. So
glyceraldehyde is carbon 1 and the
phosphate group is attached to carbon 3 so
it’s called: Glyceraldehyde-3-phosphate.
CH2OH is called dihydroxyacetone
phosphate
A three carbon ketone is known as acetone.
Fructose-1,6-bisphosphate
Again, the phosphate came from the ATP to
ADP.
Enzyme: Phosphofructokinase (PFK-1)
EQUATION: Fructose-6-phosphate +
ATP → Fructose-1,6-bisphosphate + ADP
The enzyme that catalyzes this process is
called: aldolase, used to catalyze a reversible
aldol condensation reaction.
EQUATION: Fructose-1,6-bisphosphate
→ DHAP + G3P
Step 5: Converting
dihydroxyacetone to
glyceraldehyde-3-phosphate
The relationship between the two is that they
both have 3 carbons, 5 hydrogen atoms, 6
oxygen atoms, and a phosphorus atom. They
are isomers.
A.B.
This is a rearrangement reaction, and the
enzyme that catalyzes this reaction is triose
phosphate isomerase.
Because we have 3 carbon ketone sugar.
EQUATION: DHAP → G3P
G3P has been oxidized by NAD+ to form
1,3-bisphosphoglycerate; we generate
NADH in the process. This reaction is
catalyzed by glyceraldehyde-3-phosphate
dehydrogenase.
EQUATION: G3P + NAD + Pi → 1,3bisphosphoglycerate + NADH + H+
Step 7: Substrate-level
phosphorylation
Now from step 6 - 10, we need to double
everything because of the 2G-3-P
molecules
RECALL: In step 4, we produced
dihydroxyacetone phosphate (DAP) and
glyceraldehyde 3 phosphate (G3P). In step
5, DAP was converted to G3P.
Now, 1,3-bisphosphoglycerate gives a high
energy phosphate group to ADP, resulting in
ATP. This is catalyzed by phosphoglycerate
kinase.
Step 6: Energy Harvesting Phase
Step 8: Isomerization
There’s a 3-carbon molecule still on the
right side but it’s not glyceraldehyde
anymore bcs we don’t have an aldehyde
functional group, instead we have a
phosphate group. Instead of hydrogen, we
do have oxygen, so it’s called carboxylate
group. It’s not glyceraldehyde anymore, it’s
glycerate.
3-phosphoglycerate is converted to 2phosphoglycerate. The enzyme that moves
the functional group from one position to
another is: Phosphoglycerate Mutase
Step 9: Dehydration
The 2-phosphoglycerate loses its water to
form phosphoenolpyruvate. The type of
enzyme that catalyzes this reaction is
A.B.
Enolase. (add’l info: we use enolase enzyme
bcs this reaction goes in an enolic
intermediate, enolase now facilitates the
process)
Step 10 (LAST STEP HUHU):
Substrate-level Phosphorylation
Step 10: Pyruvate Kinase
Oxidative
Phosphorylation
Phosphoenolpyruvate (PEP) gives its
phosphate group to ADP to form ATP and
pyruvate. We used pyruvate kinase for this
reaction.
DON’T BE CONFUSED!
“Asan yung phosphate group napunta?”
From the previous steps, it was transferred
to the ADP molecule to form ATP. For
every step in the payoff phase (phase II: 610), we multiply it by two to get 2 pyruvate
molecules. So, we use 2 ADP to make 2
ATP.
Remember that in the Investment Phase, we
had to use 2 ATP for the process to begin, so
in this last step we gained 2 ATP x 2 = 4 -2
(from the investment nga e) = 2 ATP
molecules in total.
SUMMARYYY!!! (ENZYMES)
Step 1: Hexokinase
Step 2: Phosphoglucose Isomerase
Step 3: Phosphofructokinase
Step 4: Aldolase
Step 5: Triose Phosphate Isomerase
Step 6: Glyceraldehyde-3-Phosphate
Dehydrogenase
Step 7: Phosphoglycerate Kinase
Step 8: Phosphoglycerate Mutase
Step 9: Enolase
Detailed Steps of Electron
Transport Chain
The last stage of cellular respiration, known
as oxidative phosphorylation, takes place in
the inner membrane of prokaryotic cells or
the mitochondria of eukaryotic cells. It
entails the connection between the
production of adenosine triphosphate (ATP),
the primary energy unit of the cell, and
electron transport. This is where the
majority of ATP is produced.
Step 1: NADH and FADH₂
Donation
Electrons from NADH and FADH₂,
produced during glycolysis and kreb’s cycle
(TCA), are donated to the Complex I of the
Electron Transport Chain.
A.B.
Step 2: Complex I (NADH
Dehydrogenase)
Step 7: Complex IV (Cytochrome c
Oxidase)
Protons (H⁺) are pumped from the matrix to
the intermembrane space across the inner
mitochondrial membrane by Complex I
(NADH dehydrogenase), which receives
electron donations from NADH.
At last, electrons are sent to Complex IV
(cytochrome c oxidase), where they mix
with protons and molecular oxygen (O₃) to
create water (H₂O). Protons are pumped
across the membrane by Complex IV.
Step 3: Coenzyme Q
(Ubiquinone)
Step 8: Proton Gradient (Proton
Motive Force, PMF)
Coenzyme Q, also known as ubiquinone, is
a mobile electron carrier that travels freely
across the inner mitochondrial membrane
and receives electrons from Complex I.
A proton gradient, or proton motive force,
PMF, is created across the inner
mitochondrial membrane by protons that are
pumped across it by Complexes I, III, and
IV.
Step 4: Complex II (Succinate
Dehydrogenase)
Step 9: ATP Synthase
Through Complex II (succinate
dehydrogenase), electrons from FADH₂—
produced in the citric acid cycle—enter the
electron transport chain (ETC). Coenzyme Q
receives electron transfers from Complex II
as well.
A potential energy differential is produced
by the proton gradient that is created in the
intermembrane space.
ATP synthase is a complicated enzyme that
is embedded in the inner mitochondrial
membrane and allows protons to flow back
into the mitochondrial matrix.
Step 5: Complex III (Cytochrome
BC-1 Complex)
Step 10: ATP Synthesis
Complex III (the cytochrome bc₁ complex)
receives electron transfers from Coenzyme
Q.
Protons are pumped across the membrane by
Complex III.
Step 6: Cytochrome C
Cytochrome c carries electrons from
Complex III to Complex IV.
ATP synthase uses the energy supplied by
protons passing through it to change ADP
(adenosine diphosphate) and Pi (inorganic
phosphate) into ATP (adenosine
triphosphate). Chemiosmotic
phosphorylation is the term for this process.
A.B.
Net Yield of each stages
(Glyco-OP)
1. Glycolysis
● Net ATP Produced: 2 ATP
● Net NADH Produced: 2 NADH
2. Citric Acid Cycle (Krebs
cycle):
● The citric acid cycle completes two
turns per glucose molecule, so
multiply the following values by 2.
● Per Turn:
● Net ATP Produced: 1 ATP
● Net NADH Produced: 3
NADH
● Net FADH₂ Produced: 1
FADH₂
3. Oxidative Phosphorylation
(Electron Transport Chain
and Chemiosmosis):
● Net ATP Produced: Approximately 3
ATP
● Net ATP Produced: Approximately 2
ATP
● Net NADH Produced: 10 NADH
● Net FADH₂ Produced: 2 FADH₂
Overall Net Yield:
● Total Net ATP from Glycolysis: 2
ATP
● Total Net ATP from Citric Acid
Cycle: 6 ATP (2 turns)
● Total Net ATP from Oxidative
Phosphorylation: Approximately 28
ATP
● Total Net ATP: 36-38 ATP
(approximately; this value can vary
based on specific conditions and the
efficiency of the transport chain)