Energy
Transformation
In the process of cellular respiration, the energy in food is
changed into energy that can be used by the body's cells.
The flow of energy starts with the sun. There are two organelles that
participate in the energy flow from the sun through living things.
Countless chemical reactions are occurring in cells to
do essential life functions with the help of ATP as the
energy currency of the cells.
What are the tasks of ATP?
• Chemical work: ATP is used for
building macromolecules
• Transport work: ATP is used for
transporting ions membranes
• Mechanical work: ATP is used for
mechanical processes such as
muscle contraction, cilia
movement
In our cells, the
energy
released
from the oxidation
of the food we eat
is stored in the
form of a “highenergy” compound
called adenosine
triphosphate (ATP).
• Adenine – is a nitrogenous base and a
part of many substances in the body
that give energy to cells.
• Ribose – is a sugar and the ratelimiting compound in the production
of
energy
compounds
called
Adenosine Triphosphate (ATP), which
are like fuel for the cells.
• Phosphate Group - The phosphate tail
of ATP is the actual power source
which the cell taps. Available energy
is contained in the bonds between
the phosphates and is released when
they are broken, which occurs
through the addition of a water
molecule
(a
process
called
hydrolysis).
Why are the
phosphoanhydride
bonds considered
high-energy?
When energy is needed
inside living cells, the
enzyme ATPase hydrolyses
the bond between the
second and third phosphate
group in ATP, removing the
third group and leaving
only two. The ATP molecule
is hydrolsed into adenosine
diphosphate (ADP) and an
inorganic phosphate ion
with the release of
chemical energy.
HYDROLYSIS OF ATP
The bonds between the phosphate groups of ATP can be broken by hydrolysis. When the terminal
phosphate bond is broken by addition of a water molecule, a molecule of inorganic phosphate
leaves the ATP, which becomes adenosine diphosphate, or ADP.
Every mole of ATP that is hydrolysed releases 30.6kJ when the bond is broken.
Chemical reactions can be classified as either exergonic
(energy outward) or endergonic (energy inward).
• An exergonic reaction proceeds with a net release of free
energy.
• An endergonic reaction is one that absorbs free energy
from its surroundings.
• If a chemical process is exergonic (downhill), releasing
energy in one direction, then the reverse process must be
endergonic (uphill), using energy. A reversible process
cannot be downhill in both directions.
ATP - ADP CYCLE
When ATP is broken
down, energy is
released and ADP is
formed.
When ADP binds with
another phosphate
group, energy is stored
and ATP is formed.
• Every task of the body requires the
use of energy. At the cellular level,
body cells need a steady supply of
energy to keep the organism alive.
• Energy is also required to produce
and breakdown molecules, as well
as to transport products in and out
of the cell. Removing pathogenic
microbes and exporting wastes out
of the cell also require the use of
energy.
• Bioenergetics is the branch of
biochemistry that focuses on how cells
transform
energy,
often
by
producing, storing or consuming
adenosine triphosphate (ATP).
Energy coupling is the transfer
of energy from one chemical
reaction to another. An
energetically favorable reaction
is directly linked with an
energetically unfavorable
reaction. Through energy
coupling, the cell can
perform nearly all of the tasks it
needs to function.