Post on 12-Sep-2021
Cellular Respiration
and Metabolism
What is Photosynthesis?
The process of using sunlight to
convert CO2 and water into
glucose and oxygen
CO2 + H2O C6H12O6 + O2
Reaction takes place in
the chloroplast
Early Experiments with Photosynthesis
• Van Helmont (1643) - plant growth does not come from soil
• Joseph Priestley (1771) - plants produce oxygen
• Jan Ingenhousz (1779) - plants need light to produce oxygen
Granum
Interior of Chloroplast
Thylakoid(contain chlorophyll)
Stroma -fluidwith enzymes
Granum
Converting Solar Energy
• Plants trap the sun’s energy using a green pigment called chlorophyll
• Chlorophyll is inside the chloroplast in the thylakoid membrane
• Solar energy is used to transform CO2 into sugars
Why are leaves green?
Only green light is
reflected
All other colors are absorbed
Chlorophyll Absorption
http://www.cbu.edu/~seisen/ChlorophyllAbsorption.jpg
Factors that Affect
Photosynthesis• Water availability
• Light intensity (varies from species to species)
• Temperature (extremes slow down photosynthesis - below 0oC and above 35oC)
Photosynthesis is divided into two processes:
Overview of Light Dependent Reactions
• Take place in thylakoidmembranes
• Require light to occur
• Produce oxygen gas
• Produce ATP and NADPH
Photosystems I and II
Clusters of light absorbing chlorophylls, other pigments and
proteins found in thylakoid membrane.
Each photosystem is connected to each other by an electron transport
chain that produces ATP
Overview of Light-Dependent Reactions
1. Light strikes Photosystem II. Energy from light excites e-
2. e- are passed through ETC to Photosystem I. Their energy is used to produce ATP (goes to the Calvin cycle)
3. Photosystem I captures light energy to re-energize e-
4. High energy e- are picked up by NADP+ to form e- carrier NADPH (goes to the Calvin cycle)
Overall schematic view of light-dependent reactions
1
4
3
2
The Calvin Cyclehappens in the stroma
Uses energy stored in ATP and
NADPH to produce glucose from
CO2.
* Six CO2 molecules from the
atmosphere are needed to
produce one glucose molecule
Summary of the Reactions of
Photosynthesis
thylakoid
stroma