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Bioenergetic Reactions
Photosynthesis & Respiration
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Bioenergetic Reactions
• Bioenergetic reactions
that occur in living things
and involve the storing
or the releasing of
energy.
• The source of energy for
all living things is the sun.
• However, most living
things cannot use energy
in this form.
• Bioenergetic reactions
create and use energy in
the form of ATP.
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What is ATP and ADP?
• The principal chemical
compound that cells use
to store and release
energy is adenosine
triphosphate, ATP.
• ATP consists of a 5carbon sugar called
ribose, and three
phosphate groups.
• Those three phosphate
groups are the key to
ATP’s ability to store and
release energy.
• ADP is a compound that
is very similar to ATP,
except it has two
phosphate groups instead
of three.
• ADP is constantly in
search of a third
phosphate to convert it to
ATP.
• ADP does not contain as
much energy as ATP.
– ADP is like a half charged
battery and ATP is like a
fully charged battery.
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Releasing
• When the chemical bond
is broken between the 2nd
and 3rd phosphate group
in ATP, a tremendous
amount of energy is
released.
• ATP has enough energy
to power a variety of
cellular activities.
– active transport across cell
membranes
– protein synthesis
– muscle contraction
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Using Biochemical Energy
• One way that cells use the
energy provided by ATP is to
carry out active transport.
• ATP is also used for the
synthesis of proteins and nucleic
acids and responses to chemical
signals at the cell surface.
• ATP is a useful source of
energy, but cells only have a
small amount of ATP.
– It is not a good molecule for storing
large amounts of energy over the
long term.
– Cells can regenerate ATP from
ADP as needed by using the
energy in foods like glucose.
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Photosynthetic Organisms
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Photosynthesis
• 6CO2 + 6H2O → C6H12O6 + 6O2
• Photosynthesis uses the energy of
sunlight to convert H2O and CO2 into high
energy sugars and oxygen.
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The Process
• Photosynthesis takes
place in the
chloroplast of the
plant.
• The reactions of
photosynthesis
occurs in two parts:
light dependent and
light-independent
(Calvin Cycle)
reactions.
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Light Dependent Reaction
• Light is required for these reactions to occur.
• This segment occurs within the thylakoid
membrane of the chloroplast.
• In Photosystem II, the energy from light is
absorbed by the chlorophyll and transferred to
the electron to energize it.
• These high-energy electrons are passed on to
the ETC.
• The energy in these electrons are used to
break up water molecules into energized
electrons, hydrogen ions, and oxygen.
– The oxygen is given to the atmosphere.
– This process is called hydrolysis.
• In Photosystem I, pigments use energy from
light to reenergize the electrons. NADPH is
formed.
• ATP is also formed at the end of this reaction.
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Light-Independent Reaction
• The light-independent reaction is
also known as the Calvin cycle.
• This reaction occurs in the stroma
of the chloroplast, which is the
region outside the thylakoid
membrane, and does not require
light.
• The ATP and NADPH from the
light dependent reaction are used
to produce high-energy sugars.
• This phase works steadily to
remove CO2 from the atmosphere
and turn out energy rich sugars.
• The plant uses the sugars to
meet its energy needs and to
build more complex
macromolecules such as
cellulose.
Chemical Energy and Food
• There is quite a bit of energy
contained in the food that we
eat.
• The process of releasing the
energy contained in the foods
that we eat begins with a
process called glycolysis.
• Glycolysis releases only a small
amount of energy.
• If oxygen is present, glycolysis
leads to two other pathways that
release a great deal of energy.
• If oxygen is not present,
however, glycolysis is followed
by a different pathway.
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Glycolysis
• For glycolysis to begin, 2
ATP’s must be borrowed
and repayed at the end.
• Glycolysis is the process in
which one molecule of
glucose is broken in half,
producing two molecules of
pyruvic acid, a 3-carbon
compound.
• The energy yield from
glycolysis is small: 2 ATP’s,
but the process itself is
quite fast.
• Glycolysis does not require
oxygen, so energy can still
be supplied when oxygen is
not available.
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Fermentation (No oxygen = Anaerobic)
Occurs outside the mitochondria
There are two types of fermentation.
http://www.5min.com/Video/How-Fermentation-Works-83226972
• Alcoholic Fermentation
– Used by yeast and a few
other microorganisms
– Produces ethyl alcohol and
carbon dioxide as wastes.
– Pyruvic acid + NADH →
alcohol + CO2 + NAD+
– This process is used by the
beer & wine industries for the
production of their products.
• Lactic Acid Fermentation
– Used by multicellular organisms and
some unicellular organisms.
– Lactic acid is produced in your muscles
during rapid exercise when the body
cannot supply enough oxygen to the
tissues.
• The buildup of lactic acid in your muscles
will make them sore!!
– Prokaryotes are used in the production
of a wide variety of foods and beverages
such as cheese, yogurt, buttermilk, and
sour cream.
– Pyruvic acid + NADH → lactic acid +
NAD+
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Organisms that do aerobic cellular
respiration
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Aerobic Cellular Respiration
• This reaction releases energy from the
chemical bonds of carbohydrates.
• This is an aerobic process which means it
requires oxygen.
• This reaction takes place in an organelle
called the mitochondria.
• Equation:
6O2 + C6H12O6
6H20 + 6CO2 + 36ATP
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The Kreb’s Cycle
• When oxygen is present
at the end of glycolysis,
the pyruvic acid passes to
the 2nd stage of cellular
respiration which is
referred to as aerobic
respiration.
• This takes place inside
the mitochondria.
• Pyruvic acid enters the
mitochondria and is
broken down into CO2,
NADH, ATP, & FADH2.
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Electron Transport Chain & Products of
Krebs and ETC
• Electron Transport Chain
– The electrons from NADH
and FADH2 are passed on to
ETC.
– The electrons convert ADP
to ATP.
– This mechanism creates the
needed energy supply.
• Products of Kreb’s & ETC
– The Kreb’s Cycle and
ETC generate 34
ATP’s.
– Remember 2 molecules
of ATP were produced
by glycolysis.
– Cellular respiration
creates 36 ATP’s for
every 1 sugar molecule
that is processed.
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Photosynthesis & Respiration
Comparison
• Used by plants and some
bacteria.
• Photosynthesis captures
energy.
• Reaction occurs in the
chloroplast.
• Reactants are CO2 + H2O.
• Products are C6H12O6 + O2.
• Equation:
6CO2 + 6H2O → C6H12O6 + 6O2
• Used by all organisms.
• Respiration releases energy.
• Reaction occurs in the
mitochondria.
• Reactants are C6H12O6 +
6O2.
• Products are ATP + CO2 +
H2O
• Equation:
C6H12O6 + 6O2 → 6CO2 + 6H2O
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