Download Understanding Photosynthesis and Cellular Respiration

Understanding Photosynthesis
and Cellular Respiration
Photosynthesis and cellular respiration are
reciprocal processes.
In other words, the products of one process
are the raw materials (reactants) of the
other process.
Do not confuse cellular respiration with
breathing.
Breathing is a physical action that helps
you get the oxygen you need to carryout
respiration which is a chemical process.
The main event of photosynthesis is food
production not oxygen production.
Oxygen is a byproduct of photosynthesis.
The main event of cellular respiration is the
release of energy from food and storing
that energy in a smaller more usable form
(ATP).
Carbon dioxide is a byproduct.
Oxygen must be present for aerobic
respiration to take place.
All organisms perform the process of cellular
respiration.
Only photosynthetic organisms (green
plants, algae, etc.) carryout the process of
photosynthesis.
During photosynthesis, the energy from the
sun is stored in the bonds of food the
product.
During cellular respiration, the energy is
released from the bonds of the food and
stored in the bonds of a smaller molecule
(ATP) for more accessible use.
The is the equation for photosynthesis:
CO2 + H2O + energy (sunlight) → C6H12O6 +
O2
This is the equation for cellular respiration:
C6H12O6 + O2 → CO2 + H2O + energy
Photosynthesis takes place in the
chloroplasts.
Cellular Respiration takes place in the
mitochondria.
Photosynthesis takes as two distinct set of
reactions:
Reactions that must take place in the
presence of light – light reactions
Reactions that may take place with or
without the presence of light – Calvin cycle
also referred to as dark reactions
Cellular respiration always begins with a
process called glycolysis – the breakdown of
glucose (food).
Glycolysis is an anaerobic process that does
not require oxygen.
Glycolysis takes place in the cytoplasm of the
cell.
Glycolysis produces a net 2 ATP molecules.
(More molecules are produced but some
must be used to supply energy to the
process).
After glycolysis takes place the molecules
produced (pyruvate or pyruvic acid) can
enter the Krebs Cycle (citric acid cycle)
which takes place in the mitochondrion.
Electrons that are produced may be
transported to the electron transport chain
in the mitochondria by carrier molecules of
NADH.
The Krebs Cycle and the electron transport
chain are part of aerobic respiration and
require oxygen to occur.
Aerobic respiration produces a net 36 ATP
molecules.
The pyruvic acid produced during glycolysis
may also be used in fermentation.
Fermentation is the process that takes place
when oxygen is not available or when the
body is using oxygen faster than it can be
supplied.
Fermentation is an anarerobic process.
There are two types of fermentation.
Lactic acid fermentation – which takes
place in muscle cells and some
prokaryotic cells.
Alcoholic Fermentation – which takes
place in yeast and a few other
microorganisms resulting in the production
of ethyl alcohol.
Anaerobic respiration only produces a net 2
ATP molecules.
Aerobic respiration is 18 times more efficient
at releasing energy from food molecules
and storing it in ATP.
Organisms that are able to carryout
photosynthesis producing their own food
are known as autotrophs or producers.
Organisms that must obtain food for energy
by eating other organisms are known as
heterotrophs or consumers.