slide show on carbon fixation

1. 1. Cut out the statements
2. Sort them into two piles and label the piles
3. Organise the piles into the correct sequence
• The electrons are donated to carrier molecules (NADP+), which is used (along with
ATP) in the light independent reactions
• The light dependent reactions occur in the intermembrane space of membranous
discs called thylakoids
• ATP and hydrogen / electrons (carried by NADPH) are transferred to the site of the
light independent reactions
• The ATP provides the required energy to power these anabolic reactions and fix
the carbon molecules together
• The light independent reactions occur within the fluid-filled interior of the
chloroplast called the stroma
• Light is absorbed by chlorophyll, which releases energised electrons that are used
to produce ATP (chemical energy)
• The hydrogen / electrons are combined with carbon dioxide to form complex
organic compounds (e.g. carbohydrates)
• The electrons lost from the chlorophyll are replaced by water, which is split
(photolysis) to produce oxygen and hydrogen

2. Step 1: Light Dependent Reactions
• Light is absorbed by chlorophyll, which releases energised electrons that are used to
produce ATP (chemical energy)
• The electrons are donated to carrier molecules (NADP+), which is used (along with
ATP) in the light independent reactions
• The electrons lost from the chlorophyll are replaced by water, which is split (photolysis)
to produce oxygen and hydrogen
• The light dependent reactions occur in the intermembrane space of membranous
discs called thylakoids
Step 2: Light Independent Reactions
• ATP and hydrogen / electrons (carried by NADPH) are transferred to the site of the
light independent reactions
• The hydrogen / electrons are combined with carbon dioxide to form complex organic
compounds (e.g. carbohydrates)
• The ATP provides the required energy to power these anabolic reactions and fix the
carbon molecules together
• The light independent reactions occur within the fluid-filled interior of the chloroplast
called the stroma

4. Remember: 2.9.S1 Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
The presence photosystems I & II and the different proportions of
of pigments explains the mismatch between the spectrums, e.g.
the double peaks in the red wavelengths of light.
The action spectrum shows the rate of
photosynthesis for all the wavelengths of
light as a % of the maximum possible rate.
%
of
the
maximum
rate
of
photosynthesis
The absorption spectrum shows the absorbance
of light by photosynthetic pigments (here
chlorophyll) for all the wavelengths of light.
http://i-biology.net/ahl/08-cell-respiration-photosynthesis/8-2-photosynthesis/

5. 8.3.U2 Light-independent reactions take place in the stroma.

6. 8.3.U3 Reduced NADP and ATP are produced in the light-dependent reactions.
ATP and NADPH (reduced NADP) are
produced by the light dependent
reactions

7. 8.3.U10 In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate.

8. 8.3.U11 Glycerate 3-phosphate is reduced to triose phosphate using reduced NADP and ATP.

9. 8.3.U12 Triose phosphate is used to regenerate RuBP and produce carbohydrates.
8.3.U13 Ribulose bisphosphate is reformed using ATP.

10. 8.3.U2 Light-independent reactions take place in the stroma.

11. Worksheets from inthinking

14. Explain how the light-independent reactions of photosynthesis rely on the light-
dependent reactions. (6 marks)

15. Explain how the light-independent reactions of photosynthesis rely on the light-
dependent reactions. (6 marks)
Light causes photoactivation / excitation of electrons;
This leads to the generation of both ATP and NADPH in the light dependent
reactions;;
The flow of electrons causes pumping of protons into thylakoid; ATP formation
when protons pass back across thylakoid membrane; ATP needed to regenerate
RuBP for use in the light dependent reactions; The photoactivated electrons are
passed to NADP / NADP+ reducing it (to NADPH);
Light-independent reaction fixes CO2 to make glycerate 3-phosphate; glycerate
3-phosphate becomes reduced to triose phosphate;
The reduction uses both NADPH and ATP;
why the colour coding?

16. New lesson

17. 8.3.U14 The structure of the chloroplast is adapted to its function in photosynthesis.
Palisade cells are found close to the top
surface of leaves. They contain a high density
of chloroplasts to enable efficient absorption
of light.

18. 8.3.U14 The structure of the chloroplast is adapted to its function in photosynthesis.
The Stroma
Contains rubisco for carboxylation of RuBP along
with all the other enzymes required for the Calvin
cycle.
Thylakoid membrane & stacked discs
(grana)
Thylakoids provide a large surface area for light
absorption and light dependent reactions
Chlorophyll (and other pigments) molecules are
grouped together to form the photosystems
which are embedded in the membrane along
with the electron carriers.
folds in thylakoid allow photosystems and
electron carriers to be close together
Thylakoid spaces
The spaces collect H+ for chemiosmosis,
the low volume enables a the H+
gradient to generated rapidly.
H+ flows back to the stroma, down the H+
gradient, through ATP synthase channels
(embedded in thylakoids membrane) to
produce ATP

19. Compare and contrast chloroplasts and mitochondria
8.3.U14 The structure of the chloroplast is adapted to its function in photosynthesis.

20. Compare and contrast chloroplasts and mitochondria
8.3.U14 The structure of the chloroplast is adapted to its function in photosynthesis.

21. 8.3.S1 Annotation of a diagram to indicate the adaptations of a chloroplast to its function.
http://www.ib.bioninja.com.au/_Media/chloroplast_med.jpeg
The three diagrams of a chloroplast show a
2D (left) and (bottom left) 3D diagrams plus a
coloured electron micrograph (bottom right).
Each diagram is labelled to show how to
identify the key structures.
Use the previous slides [8.3.U14] to add in
annotations to show how the structures are
adapted to the chloroplast’s function.

22. 8.3.S1 Annotation of a diagram to indicate the adaptations of a chloroplast to its function.

23. 8.3.S1 Annotation of a diagram to indicate the adaptations of a chloroplast to its function.

24. 8.3.S1 Annotation of a diagram to indicate the adaptations of a chloroplast to its function.
http://www.ib.bioninja.com.au/_Media/chloroplast_med.jpeg
The three different diagrams of a chloroplast
show a 2D (left) and 3D diagrams (bottom
left) plus a coloured electron micrograph
(bottom right) and how to identify the key
structures on each. Use the previous slides
[8.3.U14] to add annotations to show how
the different structures dictate its function.

25. Use the animations to learn about Calvin’s experiments
8.3.A1 Calvin’s experiment to elucidate the carboxylation of RuBP.
http://bcs.whfreeman.com/webpub/Ektron/pol1e/Animated%20Tutorials/at0
605/at_0605_pathway_co2.html
http://wps.prenhall.com/wps/media/object
s/1109/1135896/8_3.html
http://bancroft.berkeley.edu/Exhibits/Biotech/Images/3-9lg.jpg

26. 8.3.A1 Calvin’s experiment to elucidate the carboxylation of RuBP.
http://bancroft.berkeley.edu/Exhibits/Biotech/Images/3-9lg.jpg
Calvin’s experiment used Chlorella
algae which was placed in a thin glass
vessel (called the lollipop vessel). The Algae was given plenty of light, carbon
dioxide (CO2) and hydrogen carbonate
(HCO3
-) containing normal carbon (12C).
At the start of the
experiment the carbon
compounds were replaced
with compounds containing
radioactive carbon (14C).
Samples of algae were
taken at different time
intervals.
The carbon compounds were separated by
chromatography and the compounds
containing 14C identified by
autoradiography.

27. 8.3.A1 Calvin’s experiment to elucidate the carboxylation of RuBP.
http://bancroft.berkeley.edu/Exhibits/Biotech/Images/3-9lg.jpg
http://5e.plantphys.net/images/ch08/wt0802a.png
Samples were
taken at
different time
intervals
after exposure
to 14C
After only 5 seconds
there is more
labelled glycerate 3-
phosphate than any
other compound.
This indicates that
glycerate 3-
phosphate is the first
product of carbon
fixation
After 30 seconds a
range of different
labelled compounds
occur showing the
intermediate and
final products of the
light-independent
reactions
Calvin’s experiment analysed the results using
autoradiograms

28. http://bancroft.berkeley.edu/Exhibits/Biotech/Images/3-9lg.jpg
Nature of Science: developments in scientific research follow improvements in apparatus - sources
of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation. (1.8)
http://5e.plantphys.net/images/ch08/wt0802a.png
Calvin’s experiment and his subsequent discoveries
were only possible due to improvements in
technology. Key developments in that process
include:
• The discovery of 14C in 1945 by Kamen and
Ruben
• The use of Autoradiography to produce patterns
of radioactive decay emissions (autoradiograms)