Slides covering material from Topic 2.9 of the updated IB Biology syllabus for 2016 exams

1. Photosynthesis (2.9)
IB Diploma Biology
Essential Idea: Photosynthesis transforms
light energy into chemical potential
energy that can be used by organisms

2. 2.9.1 Photosynthesis is the production of carbon compounds in cells
using light energy.
Transformation of Light energy (sunlight)
into Chemical energy (carbon compounds)

3. 2.9.4 Oxygen is produced in photosynthesis from photolysis of water.
Photosynthesis occurs in two main
stages in the chloroplasts of plant cells
In the first stage, light energy is used
to split (lyse) water into oxygen and
hydrogen and make some ATP
Oxygen gas is released into the
atmosphere and Hydrogen
atoms and ATP are the used to
provide energy for the second
stage of reactions
The LIGHT DEPENDENT Reactions

4. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.
In the second stage, energy from ATP
and Hydrogen is used to transform
Carbon dioxide into Carbohydrates
Process known as Carbon Fixation
The LIGHT INDEPENDENT Reactions
(aka the Calvin Cycle)
FUN FACT: The
average tree absorbs
50 lbs of CO2 per year.
Giant Redwoods can
fix more than one
TON of carbon in
their lifetimes
The enzyme Rubisco catalyzes
this reaction series

5. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.
Light Dependent
reactions occur in
the Thylakoids
Light Independent
reactions occur in
the Stroma

6. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.

7. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.

8. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.
Starch granules

9. 2.9.5 Energy is needed to produce carbohydrates and other carbon
compounds from carbon dioxide.

10. 2.9.2 Visible light has a range of wavelengths with violet the shortest
wavelength and red the longest.

11. 2.9.3 Chlorophyll absorbs red and blue light most effectively and
reflects green light more than other colors.

12. 2.9.3 Chlorophyll absorbs red and blue light most effectively and
reflects green light more than other colors.

13. 2.9.10 Draw an absorption spectrum for chlorophyll and an action
spectrum for photosynthesis.

14. 2.9.10 Draw an absorption spectrum for chlorophyll and an action
spectrum for photosynthesis.

15. 2.9.10 Draw an absorption spectrum for chlorophyll and an action
spectrum for photosynthesis.

16. 2.9.10 Draw an absorption spectrum for chlorophyll and an action
spectrum for photosynthesis.

17. 2.9.9 Separation of photosynthetic pigments by chromatography.
Chromatography is an method of
separating out different pigment
molecules based on their solubility
It can be used to separate and
distinguish chlorophyll and other
accessory pigments, such as
carotene and xanthophyll

18. 2.9.6 Temperature, light intensity, and carbon dioxide concentration
are possible limiting factors on the rate of photosynthesis.

19. 2.9.6 Temperature, light intensity, and carbon dioxide concentration
are possible limiting factors on the rate of photosynthesis.

20. 2.9.6 Temperature, light intensity, and carbon dioxide concentration
are possible limiting factors on the rate of photosynthesis.

21. 2.9.6 Temperature, light intensity, and carbon dioxide concentration
are possible limiting factors on the rate of photosynthesis.

22. 2.9.6 Temperature, light intensity, and carbon dioxide concentration
are possible limiting factors on the rate of photosynthesis.

23. 2.9.8 Design experiments to investigate limiting factors on
photosynthesis.

24. 2.9.8 Design experiments to investigate limiting factors on
photosynthesis.

25. 2.9.7 Changes to the Earth’s atmosphere, oceans, and rock deposition
due to photosynthesis.
Early Earth’s reducing atmosphere
contained negligible amounts of oxygen.
The first prokaryotes emerged around
3.5 BYA, but it wasn’t until about 2.2 BYA
that oxygen levels rose to 2%.
Known as the Great Oxidation Event
Thanks, Photosynthesis!!

26. 2.9.7 Changes to the Earth’s atmosphere, oceans, and rock deposition
due to photosynthesis.
Oxygen rise caused drops in Methane
and CO2 (GHGs!) which corresponded
with Earth’s first glaciation. BRRR!
Thanks, Photosynthesis!

27. 2.9.7 Changes to the Earth’s atmosphere, oceans, and rock deposition
due to photosynthesis.
Corresponding oxidation of dissolved iron in the oceans
allowed iron ore to precipitate, forming bands across the
seafloor and providing a source of iron and steel to this day
Thanks, Photosynthesis!

28. 2.9.7 Changes to the Earth’s atmosphere, oceans, and rock deposition
due to photosynthesis.
Oxygen rise to 20% atmospheric concentration
around 600-700 MYA allowed for the “Cambrian
Explosion” of multicellular speciation
Thanks, Photosynthesis!
…and Aerobic Respiration!

29. Bibliography / Acknowledgments
Jason de Nys
Chris Paine