1. Photosynthesis
Introduction

2. What is photosynthesis?
Photosynthesis: to capture light energy from the sun and convert it to chemical energy stored in sugars and other organic molecules
Photosynthesis occurs in plants, algae, some other protists, and some prokaryotes
Nourishes almost all of the living world directly or indirectly!

3. Autotrophs
Autotroph: an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms
They make their own food!
Autotrophs can be separated by the source of energy that drives their metabolism.
Photoautotrophs use light as the energy source.
Chemoautotrophs harvest energy from oxidizing inorganic substances, including sulfur and ammonia.
Chemoautotrophy is unique to bacteria.

4. Heterotrophs
Heterotroph: an organism that obtains organic food molecules by eating other organisms or their byproducts
Consumers of the biosphere
Some feed on plants and other
animals.
Others decompose and feed on
dead organisms and on organic
litter, like feces and fallen leaves.
Almost all depend on photoautotrophs
for food and for oxygen, a byproduct
of photosynthesis.

5. Where does photosynthesis take place?
Chloroplasts are the site of photosynthesis in plants
half a million chloroplasts per square millimeter of leaf surface!
Chlorophyll: the green pigment in the chloroplasts.
important for the absorption
of light energy during
photosynthesis

6. Leaf Anatomy Mesophyll: the tissue in the interior of the leaf
Where chloroplasts are found
Stomata: microscopic pores that allow CO2 to enter and O2 to exit the leaf
Veins: deliver water from the roots and carry off sugar from mesophyll cells to other plant areas.

7. Chloroplast Parts
Each chloroplast has two membranes around a central aqueous space, the stroma.
In the stroma are membranous sacs, the thylakoids.
Inside area is called
the thylakoid space
Stacked into grana

8. The Equation
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
hydrogen extracted from water is incorporated into sugar along with the carbon dioxide
the oxygen is released to the atmosphere
Photosynthesis is a redox reaction.
reverses the direction of electron
flow in respiration
Water is split and electrons
transferred with H+ from water
to CO2, reducing it to sugar.

9. 1. Light Reactions: Overview
light reactions: convert solar energy to chemical energy
light energy absorbed by chlorophyll in the thylakoids drives the transfer of electrons and hydrogen from water to NADP+,forming NADPH.
NADPH, an electron acceptor, provides energized electrons, reducing power, to the Calvin cycle.
also generates ATP by photophosphorylation for the Calvin cycle
occurs in the thylakoids

10. 2. Calvin Cycle: Overview
Calvin cycle: incorporates CO2 from the atmosphere into an organic molecule and uses energy from the light reaction to reduce the new carbon piece to sugar.
begins with the incorporation of CO2 into an organic molecule via carbon fixation
carbon backbone is reduced with electrons provided by NADPH
ATP from the light reaction
also powers parts of the
Calvin cycle
occurs in the stroma

11. Review Draw a diagram of the chloroplast. Label all the parts.
Label where the light reaction and the Calvin cycle (dark reaction) occur.
Write a detailed three-sentence summary of photosynthesis.