Photosynthesis and
Cellular Respiration
Photosynthesis

Photosynthesis takes place in specialized
structures inside plant cells called chloroplasts
–
Light absorbing pigment molecules e.g. chlorophyll
Overall Reaction

6CO2 + 12 H2O + light
energy → C6H12O6 + 6O2+ 6H2O

Carbohydrate made is glucose
Water appears on both sides because 12 H2O molecules
are required and 6 new H2O molecules are made
Water is split as a source of electrons from hydrogen
atoms releasing O2 as a byproduct
Electrons increase potential energy when moved from
water to sugar therefore energy is required



Two Parts of Photosynthesis
4
1.Light Reaction or Light
Dependent Reaction Produces energy from solar
power (photons) in the form of
ATP and NADPH.
SUN
Splits waterreleases O2
Two Parts of Photosynthesis
2. Calvin Cycle or
Light
Independent
Reaction
 Takes
CO2 and
makes sugar
 Uses energy (ATP
and NADPH) from
light reactions
5
Harvesting Chemical Energy




So we see how energy enters food chains (via
autotrophs) we can look at how organisms use
that energy to fuel their bodies.
Plants and animals both use products of
photosynthesis (glucose) for metabolic fuel
Heterotrophs: must take in energy from outside
sources, cannot make their own e.g. animals
When we take in glucose (or other carbs),
proteins, and fats-these foods don’t come to
us the way our cells can use them
Cellular Respiration- getting
energy from food in form of ATP
Cellular Respiration Overview



Sugar from food is transformed into ATP
These reactions proceed the same way in plants and
animals
Overall Reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O +36 ATP
Glucose+ oxygen carbon dioxide+water+ATP
1.Glycolysis






Glycolysis (glyco=sugar;lysis=breaking)
Gain 2 ATP
Who: all life on earth does it
Goal: break glucose down to form two pyruvates
Where: the cytoplasm
Glycolysis produces two 3-carbon molecules and
a net of 2 ATP and 2 NADH
2. Krebs Cycle 


carbon molecules are broken into CO2
Gain 2 ATP
In the mitochondria
3. Electron Transport Chain



High energy electrons from glycolysis and krebs
turn ADP into ATP
Oxygen accepts the electrons and turns into
water
Gain 32 ATP
1.
2.
3.
4.
5.
6.
Where does cell respiration happen?
What are the 3 steps?
Which step provides the most ATP?
What step do you need oxygen for?
When do you make CO2?
How is it related to photosynthesis?