This presentation is all about Cellular Energy Transfer with reference to Glycolysis and Kreb Cycle with all their stages involved. It also includes ATP production in the body, its importance, structure. Also contains a comparison of energy production in Krebs and Glycolysis cycle.

2. CELLULAR ENERGY TRANSFER
Glycolysis & Oxidative
Decarboxylation of pyruvate
Several distinct but linked metabolic pathways are
used by cells to transfer the energy released by
breakdown of fuel molecules into ATP & other
small molecules used for energy , such as GTP,
NADPH, FADH etc.
The metabolic pathways occur within all living
organisms in some form are:
●Glycolysis
●Oxidative decarboxylation of pyruvate
●Citric acid cycle /Krebs cycle
●Oxidative phosphorylation

3. DEFINATION:
‘Glycolysis is a metabolic pathway that converts
glucose into pyruvate.’
The energy released in this process is used to
form the high energy compounds ATP & NADPH.
Glycolysis occurs nearly in all organisms both
aerobic & an-aerobic.
This indicates glycolysis is so ancient.
PHASES OF GLYCOLYSIS:
The entire glycolysis pathway can be separated into
2-phases
1-THE PREPARATORY PHASE
2-THE PAY - OFF PHASE

4. THE PREPARATORY
PHASE:
DEFINATION: ‘The preparatory phase Or investment
phase consume energy to convert the glucose into
2-molecules of three carbon phosphates (G3P)’.
EXPLANATION:The first step in glycolysis is
phosphorylation of glucose by a family of enzymes
called ‘hexo-kinase’ to form glucose 6-phosphate
(G6P). This reaction consumes ATP but it acts to
keep the glucose concentrations low, in addition it
blocks the glucose from leaking out, of the cell &
free diffusion out of the cell is prevented due to
charged nature of G6P. G6P is then rearranged into
Fructose 6-phosphate (F6P) by an enzyme ‘glucose
phosphate isomerase’. Here isomerization occurs by
which G6P structurally converted into F6P the
reaction requires an enzyme, ‘phosphohexose
isomerase’ to procceed. The glycolytic process is
now irreversible & the energy supplied de-stablized
the molecule. De-stablization of the molecule in the
reaction allows the hexose ring to be split by

5. The enzyme Triphosphate isomerase rapidly
interconverts the above sugars that proceed further
into glycolysis.
THE PAY-OFF PHASE:
DEFINATION:
‘The second half of glycolysis is known as the pay
off phase characterized by a net gain of the
energy-rich molecules ATP and NADH.’
EXPLANATION:
The triose sugar s are dehydrogrnated & inorganic
phosphate is added to them forming 1,3-
bisphosphoglycerate. The hydrogen is used to reduce
2molecules of NAD+ (a hydrogen carrier) to give
NADH+ + H+ for each triose. This step is the
enzymatic transfer of a phosphate group from 1,3-
bisphosphoglycerate to ADP by an enzyme
phosphoglycerate kinase, forming ATP & 3-
phosphoglycerate. At this step glycolysis has reached
the break point, 2molecules of ATP were consumed

6. At the end a final substrate level
phosphorylation now forms a molecule of pyruvate
& a molecule of ATP by means of an enzyme
pyruvate kinase.

7. Oxidative Decarboxylation of Pyruvate:
EXPLANATION:
By the action of pyruvate dehydrogenase complex
the pyruvate oxidized to acetyl coA & CO2 .
The PDC contains multiple copies of 3-enzymes
& is located in the mitochondria of eukaryotic
cells & in the cytosol of prokaryotes . In the
conversion of pyruvate to acetyl coA , one
molecule of NADH & one molecule of CO2 is
formed.

8. KREB
CYCLEINTRODUCTION:
This is also called citric acid cycle or the
tricarboxylic acid cycle.
When oxygen is present acetyl coA is produced
from the pyruvate molecules, which are created
by glycolysis. When oxygen is present the
mitochondria will undergo aerobic respiration which
leads to the krebs cycle. However, if oxygen is
absent fermentation of pyruvate molecule will
occur. In the prescence of oxygen when acetyl coA
is produced, the molecule then enters the krebs
cycle inside the mitochondrial matrix and gets
oxidized to CO2 & reduced NAD to NADH. 2-
WASTE products are created during this cycle
such as H2O & CO2

10. involving different enzymes & co-enzymes.
During the cycle acetyl coA combines with
the precursor molecule oxaloacetate (having
four carbons). Citrate then rearrange itself to
a more reactive form called iso-citrate
(having 6-carbons). Isocitrate further modified
to become @-ketoglutrate (having 5-carbons) .
Then it will converts to succinate. Succinate
will further form fumarate. Fumarate then
converts into malate & finally precursor
oxaloacetate.
The net gain of high
energy compounds from one cycle is
3NADH,1FADH2 & 1GTP, the GTP may
subsequently be used to produce ATP.Thus
the total yeild from 1-glucose molecule

11. Oxidative phosphorylation
In eukaryotes, oxidative phosphorylation occurs in
the mitochondrial cristae. It comprises the
electron transport chain that establishes a proton
gradient across the boundary of inner –membrane
by oxidizing the NADH produced from the krebs
cycle.
ATP is synthesized by the ATP –synthase
enzyme, when the chemi-osmotic gradient is used
to drive the phosphorylation of ADP. The
electrons are finally transferred to oxygen & by
the addition of 2protons, water is formed.

12. AT
PAdenosine Triphosphate (ATP) is nucleoside triphosphate
used in cells as a co-enzyme often called the ‘Molecular
unit of currency’ of intracellular energy transfer. ATP
transport chemical energy within cells for metabolism.
It is one of the end products of
photophosphorylation, cellular respiration &
Fermentation’.
ATP used by enzymes and structural proteins, in
many cellular processes includes, Biosynthesis or
Biosynthetic reactions, motility and cell division.
Substrate level phosphorylation, oxidative phosphorylation
in cellular respiration and photophosphorylation in
photosynthesis are 3-major mechanisms, of ATP
biosynthesis.
Molecular formula is C10H16N5O13P3

13. STRUCTURE OF
ATP:One molecule of ATP contains 3-phosphate groups
and it is produced by a wide variety of enzymes
including ATP-synthase
1-From ADP or AMP
2-And from various phosphate group donors.
The structure of ATP consists of purine base
(Adenine) attached to the 1-carbon atom of pentose
sugar. 3-phosphate groups are attached at 5-carbon
atom of the pentose sugar.
ATP consists of adenosine composed of an adenine
ring and a Ribose sugar and 3-phosphate groups
(Triphosphate).
The phosphoryl groups, refers to as alpha, beta and
gamma phosphates.
It is the addition and removal of these phosphates
groups that interconvert ATP, ADP, & AMP.

14. PHOSPHATE
GROUPS:
Two phospho-anhydride bonds those that connect
adjacent phosphates in an ATP molecule are
responsible for the high-energy content of this
molecule.
In biochemical reactions, these anhydride bonds are
frequently and sometimes controversially, referred to
as ‘’high energy bond’’.
Energy stored in ATP may be released upon
hydrolysis of anhydride bonds.
The primary phosphate group on the ATP molecule
is gamma-phosphate and it is hydrolysed , when
energy is needed to drive anaerobic reactions.
Gamma-phosphate located farthest from the ribose
sugar but it has a higher energy of the hydrolysis
than either the alpha or beta phosphate.

15. CHARACTERISTICS OF
ATP:
ATP is highly soluble in water.
ATP is quite stable in solutions between pH 6.8 to
7.4
ATP is rapidly hydrolysed at extreme pH.
ATP is best stored as an anhydrous salt.
ATP is an unstable molecule in un-buffered water,
in which it hydrolyses to ADP and phosphate.
Because the strength of bonds between the
phosphate groups in ATP is less than the strength
of the hydrogen bonds between its products (ADP +
phosphate) and water.

16. BIO-SYNTHESIS:
The ATP concentration inside the cell is typically 1-
10 m.
ATP can be produced by redox reactions using
simple and complex sugars carbohydrates or lipids
as an energy source.
Complex fuels to be synthesized into ATP , they
first need to be broken down into smaller, more
simple molecules.
ATP can be produced by a no# of cellular
processes.
The 3- main pathways used to generate energy in
eukaryotic organisms are:
1. Glycolysis 3. Krebs cycle
2. Cellular respiration can produced about 30molecules
of ATP from a single glucose molecule.
3. Oxidative phosphorylation

17. ATP production in Glycolysis:
In the process of Glycolysis
ATP substrate level= 2ATP molecules are obtained
And via ETC =2NADH molecules are
obtained = 6 ATP
HENCE, total ATP =6ATP & 2ATP are utilized as
energy sourceATP production in pyruvate oxidation:
In the process of pyruvate oxidation
At substrate level = No, ATP is obtained
At via ETC =2NADH =6ATP
Hence , total ATP = 6 ATP molecules are obtained
ATP production in KREB CYCLE:
At Substrate level =2 ATP
And via ETC =6NADH=18ATP
=2FADH2=4ATP

18. ATP production during
photosynthesis
In plants ATP is synthesized in thalakoid membrane
of the chloroplast during the light dependent
reactions of photosynthesis in a process called
‘’photoposphorylation’’ .
Here light energy is used to pump protons across
the chloroplast membrane.This produces a proton
force and thus the ATP synthase.
Some of the ATP produced in the chloroplast is
consumed in the clavin cycle.ATP RE-
CYCLINGThe total quantity of ATP in human body is about
0.2mole. The used by human cells requires the
hydrolysis of 100 to 150 moles of ATP daily ,which
is around 50 to 75kg. A human will typically use up
his or her body weight of ATP over the course of
the day.
This means that each ATP molecule is recycled
500-750 times during a single day. ATP cannot be
stored hence, its consumption closely follow its

19. ROLE IN CELL STRUCTURE &
LOCOMOTION
ATP is involved in maintaining cell structure by
facilitating assembly and disassembly of elements of
the cytoskeleton.
ATP is required for shortening f actin and myosin
filament across bridges required for muscle
contraction. This process is one of the main energy
requirment of animals and is essential for
locomotion and respiration.ROLE IN METABOLISM SYNTHESIS &
ACTIVE TRANSPORT
ATP is the main energy source for the majority of
cellular functions. ATP is consumed in cell by
endothermic processes and can be generated by
exothermic processes .
In this way ATP is transfers energy between
separate metabolic reactions. ATP includes synthesis
of macromolecules including DNA and RNA and
proteins.