Photosynthesis (2.9)IB Diploma Biology

Essential Idea: Photosynthesis transforms light energy into chemical potential

energy that can be used by organisms

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)

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

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

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

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

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

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

Starch granules

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

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

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

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

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

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

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

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

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

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

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

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

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

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

2.9.8 Design experiments to investigate limiting factors on photosynthesis.

2.9.8 Design experiments to investigate limiting factors on photosynthesis.

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!!

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!

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!

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!

Bibliography / Acknowledgments

Jason de Nys

Chris Paine