Calvin Cycle
Characteristics of Calvin
Cycle
• Similar to KC because starting material is
regenerated
• Anabolic and endergonic, takes place in the stroma
of the chloroplast
• C enters as carbon dioxide and leaves as a sugar
• ATP is energy source
• NADPH is reducing agent to the sugar
• Direct carbohydrate product is G3P,
glyceraldehyde 3-phosphate (also known as
PGAL)…for one G3P, the Calvin cycle must “spin” 3
times “fixing” 3 carbon dioxide molecules
3 phases of the Calvin Cycle
• 1. Carbon Fixation – each CO is
attached to ribulose biphosphate
(RuBP) by an enzyme called Rubisco 
most abundant protein on Earth,
making 2 molecules of 3phosphoglycerate per CO
2
2
• 2. Reduction –
– Each molecule is phosphorylated via ATP
and becomes 1-3-biphosphoglycerate
(total here is six! …2/each of the three
CO …therefore, requiring 6 ATP)
– Next NADPH reduces 1-3biphosphoglycerate to G3P (6 NADPH
making 6 G3P)
– Only one G3P exits cycle here
2
• 3. Regeneration of CO acceptor RuBP
2
– 5 remaining G3P use 3 ATP to rearrange
into 3 RuBP
– The G3P that exited the Calvin cycle will
be used in biosynthesis for glucose and
other organic molecules
• For one G3P molecule, how many CO ,
ATP, and NADPH molecules are
needed?
2
– 3 CO2
– 9 ATP
– 6 NADPH
• To make a glucose molecule, how many
CO2, ATP, and NADPH molecules are
necessary?
- 6 CO
- 18 ATP
- 12 NADPH
2
• Where do the ADP and NADP+ go
that have been “recycled” due to the
Calvin cycle?
– To be used in the light reactions in the
thylakoid membranes
The Calvin Cycle
Calvin Cycle Animation
• http://www.youtube.com/watch?v=mH
U27qYJNU0
Lab 4 Photosynthesis
• This lab will measure the rate of
photosynthesis
• Under normal conditions an excited
electron will move through the ETC
and reduce _______.
Lab 4 Photosynthesis
• This lab will measure the rate of
photosynthesis
• Under normal conditions an excited
electron will move through the ETC
and reduce NADP+.
• What is going to happen in this lab?
What
happens
as light
hits the
reaction
center?
DPIP
The
DPIP will
be
reduced,
and it
will go
from
blue to
colorless
DPIP
How will we measure the rate of reduction of
DPIP?
Tips for Success
• Be sure to add all materials to each
cuvette, except the chloroplasts
• Add chloroplasts to your blank
cuvette and calibrate the
spectrophotometer
• Once the machine has been
calibrated, add chloroplasts to one
cuvette and immediately take your
first reading.
• Use “kim wipes” to keep cuvettes
clean.
• Mix each sample before you read it
• Orient the cuvettes in the spec the
same way each time you read them.
• Keep all tubes a constant distance
from the light source.
• Remove the “dark” cuvette from the
foil before getting each reading.
Predict Results: