Understanding
Photosynthesis
Scientific Discoveries and nature of light
ATP Molecule

Adenosine Triphosphate ( ATP )

Consists of adenine, ribose (5-carbon sugar) and three phosphate groups (PO4)

The bond between the last two phosphate groups stores 8,000 calories

The bond between the ribose and first phosphate stores 2,200 calories
Understanding Photosynthesis
 Carbon
 6CO2
dioxide + water = sugars + oxygen
+ 6H2O
light
C6H12O6 + 6O2

Plants need chlorophyll and accessory pigments to
absorb light
Jan Baptista van Helmont (1600’s)
He grew a willow tree and measured the amount of soil,
the weight of the tree and the water he added. After
five years the plant had gained about 164 lbs (74 kg).
Since the amount of soil was basically the same as it had
been when he started his experiment, he deduced that
the tree's weight gain had come from water. Since it had
received nothing but water and the soil weighed
practically the same as at the beginning, he argued that
the increased weight of wood, bark and roots had been
formed from water alone.
John Woodward
(1600’s)
a professor and physician at Cambridge University in the
late 17th century, tried to design an experiment to test
the hypothesis that water was the source of the extra
mass. In a series of experiments over 77 days, Woodward
had seen the same results as this study and he also
rejected the hypothesis that plant growth comes from
water.
Joseph Priestley

Mass of plants comes from air!
(1770’s)
Jan Ingenhousz

(1770’s)
Light is essential for plants to “restore” air
Jean Senebier

(1790’s)
Demonstrated that green plants consume carbon dioxide and release oxygen under the influence
of light
F. F. Blackman
( 1900 )
Since the rate of photosynthesis does not continue to
increase indefinitely with increased illumination,
Blackman concluded that at least two distinct processes
are involved: one, a reaction that requires light and the
other, a reaction that does not.
C.B. Van Neil

(1930’s)
Studying photosynthesis in purple sulfur bacteria, he discovered that
the source of hydrogen in carbohydrates came from the splitting of the
water molecule (photolysis).
Melvin Calvin(1948)

Traced radioactive CO2 through photosynthetic algea

Found that the radioactive carbon binds with ribulose bisphosphate

This is the first step of the “calvin cycle” or light independent reactions
Introduction video

http://www.bing.com/videos/search?q=photosynthesis&FORM=HDRSC3&adlt=
strict#view=detail&mid=F9B1CAB3AB9ECBB7CDABF9B1CAB3AB9ECBB7CDAB
Electromagnetic Spectrum
Light absorption by plants
Chromotography
Chloroplast
The Light Independent Reactions

Also known as the “Calvin Cycle”

Uses ATP and NADPH generated by the light
reactions

Occurs in the stroma of the chloroplast

Uses carbon dioxide from stomates of plant

Creates sugar molecules and regenerates ribulose
biphosphate
Calvin Cycle
Overview of Photosynthesis
Do not panic! This video will
cover the entire process of
photosynthesis, we will take the
time to learn one portion at a
time!