The process of plants using the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen. 6 CO 2 + 6H 2 O + Light energy  C 6 H 12 O O 2 Carbon dioxide + water sugars + oxygen The process of plants using the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen. 6 CO 2 + 6H 2 O + Light energy  C 6 H 12 O O 2 Carbon dioxide + water sugars + oxygen light

Review of Cellular Respiration and Photosynthesis Processes

Plants Unicellular protist Multicellular algaeCyanobacteria Purple sulfur bacteria 10 µm 1.5 µm 40 µm Photosynthesis occurs in plants, algae, certain other protists, and some prokaryotes These organisms feed not only themselves but also the entire living world

In addition to water and carbon dioxide photosynthesis requires light and chlorophyll. Chlorophyll absorbs blue and red light best. This is the visible spectrum of light.

Photosynthesis does not absorb light in the green region well. Green light is reflected by leaves, which is why plants look green. There are other pigments in plant cells that help with photosynthesis. There are two different types of chlorophyll pigments and other pigments that absorb light in other wavelengths. Think about it, what color do leaves turn in the fall?

Leaf cross section Vein Mesophyll Stomata CO 2 O2O2 Mesophyll cell Chloroplast 5 µm Outer membrane Intermembrane space Inner membrane Thylakoid space Thylakoid GranumStroma 1 µm 1.Leaves are the major location for photosynthesis 2.Green color is from chlorophyll-the pigment in chloroplasts – absorbs light energy 4. Stomata – CO2 and O2 will enter and leave through these pores on the underside of the leaves. 3.The chlorophyll is in the thylakoids Thylakoids are stacked into granum The fluid that fills the chloroplast is the stroma Site of Photosynthesis – The Chloroplast

Light-dependent reactions – Convert the energy in sunlight to chemical energy Light – independent reactions – Calvin Cycle Makes sugar

LE 10-5_3 H2OH2O LIGHT REACTIONS Chloroplast Light ATP Electron carriers O2O2 Electron carriers + CO 2 ADP P + i CALVIN CYCLE [CH 2 O] (sugar) The Calvin Cycle llight Overview of Photosynthesis

Photosystems Light Dependent Reactions

How Photosystems Work Light “hits” the photosystem Electrons become “excited” “passes” electrons from one chlorophyll to another Electrons arrive at Electron Acceptor and then move onto the next photosystem Photosystem Light Electron acceptor

Light Dependent Reactions at the First Photosystem Takes place in the thylakoid Photosystem traps light energy Light excites electrons (within the photosystem) Electrons move down electron transport chain to next photosystem The electrons must be replaced by splitting a water molecule (H 2 O) O 2 is released H+ are produced

Light Reactions-First Photosystem H2OH2O Light First Photosystem O2O2 H+ The light-excited electrons from chlorophyll travel down the chain Stroma Thylakoid compartment H+

Light Dependent Reactions at the Second Photosystem Electrons arrive at the second photosystem. H+ ions continue to build up in thylakoid space Hydrogen ions diffuse through ATP synthase creating ATP energy ATP moves to Calvin Cycle Electrons are picked up by Electron carriers which move to Calvin Cycle (Honors Bio the electron acceptor is NADP once it accepts the electrons it becomes NADPH)

Light Reactions at second photosystem H2OH2O Light First Photosystem O2O2 H+ Second Photosystem Electrons Electron carrier molecule ATP H+ P Calvin Cycle Light H+ Thylakoid compartment Stroma H+

Review of Light Reactions

Light Dependent Reactions Electron carrier molecule Summary Require what 2 things to get started? Take place where? What 3 things are produced? What 2 things are produced that move onto the Calvin Cycle?

Light Independent Reactions The Calvin Cycle Takes place in the stroma of the chloroplast Produces sugars The starting material is regenerated with each turn of the cycle CO 2 enters the cycle and is bonded to a 5 – carbon sugar – This process is aided by an enzyme called Rubisco

The Calvin Cycle Carbon from CO2 5-C sugar End up with the 5-C sugar again Rubisco ATP Electron carriers(NADPH) helps to break and reform this 5-C sugar, along with ATP from the light dependent reactions

The Calvin Cycle With each turn of the cycle there are inputs and outputs. Inputs are: – Carbon dioxide from the air – Electron carrier molecule (Honors Bio-NADPH) from light reactions – ATP from light reactions Outputs – An energy rich sugar named G3P G3P is the raw material used to make glucose and other organic molecules.

The Calvin Cycle G3P sugar Electron carrier molecule Molecule that becomes electron carrier

Photosynthetic Products Sugar – Supplies plant with chemical energy Use sugars for cellular respiration – Building block of cell parts

Factors Affecting Photosynthesis Availability of water Temperature Intensity of light – Increasing the intensity of light increases the rate of photosynthesis. – Review with slideshow - campbell