Photosynthesis Sun ~ ultimate source of energy for all living things. The energy of the sun must be converted into chemical energy so that it can be used. Photosynthesis ~ the process of absorbing light energy and converting it into stored chemical energy. Green plants, algae, and some bacteria produce enough chemical energy for all living things, not just themselves. Photosynthesis also produces oxygen, which is of vital importance to living things.

Visible Light Part of the electromagnetic spectrum Behaves like a wave and a particle Different electromagnetic waves and different colors of light have different wavelengths and frequencies Wavelength is related to the amount of energy long wavelength = low frequency = low energy short wavelength = high frequency = high energy

Chlorophyll Chlorophyll ~ green pigment , the primary catalyst of photosynthesis. Pigments- special light-absorbing molecules Iron must be present in the plant for the production of chlorophyll. If a plant is lacking chlorophyll, it will be yellowish or whitish. Chlorophyll is found in the membranes of the grana of the chloroplast. There are other pigments considered accessory pigments. All accessory pigments absorb wavelengths of light energy that chlorophyll can’t absorb, and pass that energy to chlorophyll to be used in photosynthesis. Plants appear green because chlorophyll absorbs other colors but reflects green light.

Plant Structures Leaf Mesophyll cells- special photosynthetic cells Chloroplast- green organelle found in plants, special plastid that is the site of photosynthesis Stroma- material within the chloroplast that surrounds the grana Granum (grana)- stacks of thylakoids Thylakoid- Flattened sacs inside the chloroplast Stomata (Stoma)- openings in the leaves of plants that allows CO2 to enter the leaf and O2 to exit.

Light Dependant Phase aka light reactions, energy fixing reactions Occurs in the thylakoid membrane Includes Photosystem II and Photosystem I (Photosystem I actually comes second, but it was discovered first) Materials: Light energy Water Chlorophyll and other pigments Primary electron acceptors Electron Transport Chains- series of protein molecules that pass along electrons ATP synthase Products: Oxygen NADPH (electron carrier) ATP (chemical energy)

Light Dependent Phase Photosystem II Pigments absorb light energy in Photosystem II Energy is passed from pigment molecule to pigment molecule till it reaches two special chlorophyll molecules. Energy excites the electrons in the chlorophyll molecule and the electrons are transferred to the primary electron acceptor (Water is split into 2 hydrogen ions (protons), 1 oxygen, and 2 electrons- the electrons replace the excited electrons) The primary electron acceptor passes the electrons to an electron transport chain Energy is slowly released from the electrons as they are passed from protein to protein. That energy is used to make ATP via a process called chemiosmosis. Chemiosmosis- Hydrogen ions are actively transported across the thylakoid membrane to create a high concentration. Then they diffuse through ATP synthase from high concentration to low concentration and ATP synthase synthesizes ATP.

Light Dependent Phase Photosystem I Pigments absorb light energy in Photosystem I Energy is passed from pigment molecule to pigment molecule till it reaches two special chlorophyll molecules. Energy excites the electrons in the chlorophyll molecules and the electrons are transferred to the primary electron acceptor (electrons from Photosystem II replace these electrons) The primary electron acceptor passes the electrons through an electron transport chain Electrons reach an NADP+ molecule and it is converted to NADPH

Light Dependent Phase Diagram

Calvin Cycle Aka light independent phase, carbon fixing reactions Occurs in the stroma Materials needed for light-independent phase ATP from light reactions (chemical energy) NADPH from light reactions (electron carrier) Carbon dioxide from atmosphere (carbon source) RuBP, rubulose bisphosphate Rubisco (enzyme) Products of light-independent phase: PGAL RuBP is recycled

Calvin Cycle Rubisco joins CO2 from the atmosphere with RuBP ATP and NADPH from the light reactions are used to make several conversions and eventually produce PGAL (intermediate molecule that can be used to make glucose and other organic molecules) RuBP is recycled

Conditions Conditions for Photosynthesis: Light ~ adequate quantities of the right wavelengths & intensity of light needed to energize electrons CO2 ~ seldom a problem, because the atmosphere provides plenty Temperature ~ appropriate temp. varies from plant to plant Water Chlorophyll ~ and occasionally accessory pigments. We talked about how plants need iron because it aids in the production of chlorophyll

http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/environment/1_food_factory1.shtml http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/068/Rate%20of%20photosynthesis%20limiting%20factors.pdf