Discovering Photosynthesis  Van Helmont- wanted to know if plants grow by taking stuff out of the soil  Concluded the weight came from the water (hydrate).  Priestley- found that something made by plants allows a candle to burn in a jar  Plants release oxygen!  Jan Ingenhousz- found that Priestley’s experiment only works if sunlight is available  Plants need sunlight to produce oxygen  We need H 2 O, light and carbon dioxide to do photosynthesis 6 CO H 2 O + energy  C 6 H 12 O 6 + 6O 2

Structure of Photosynthesis- Chloroplast  Thylakoid- photosynthetic membranes containing photosystems  Photosystem- chlorophyll, other pigments and proteins  Grana- a stack of thylakoids  Stroma- space outside thylakoids  Lamella- connective material holding thylakoids in place

Photosynthesis in 2 parts  Light-dependent reactions  Needs light to happen  Happens inside the thylakoid membranes  Calvin Cycle  Also called the light-independent reactions  Does not need light to happen, but does need the products from the light cycle  Happens in the stroma

Atom Recall  What are the positive particles, negative particles and neutral particles in an atom called?  Protons, electrons and neutrons  What is an ion?  An atom or compound that has a + or - charge due to losing or gaining e - s  If an ion has more protons than e - s, is the charge - or +?  Positive

NADPH  When the sunlight hits chlorophyll it excites free e - s  Carrier molecule: A compound that can accept a pair of high-energy e - s and transfer them and their energy to another molecule  NADP + accepts 2 e - and 1 H +  NADPH  An H atom consists of 1 e - and 1 proton (H + )  NADP + and H + = +2  2 e - = -2  Now it carries the high energy electrons made by light absorption in chlorophyll  How does ATP store energy?

Light-Dependent Reactions  Uses sunlight to convert ADP and NADP + to ATP and NADPH Noncyclic NADPH and ATP Formation Cyclic and Noncyclic, Light-dependent reactions

Summary of Light-Dependent Reactions 1.Pigments in Photosystem (ps)II absorb light energy which excites e - s 2.High-energy e - s are passed along the electron transport chain 3.More e - s are made by splitting water molecules, releasing oxygen into the air and H + in the thylakoid space 4.High-energy e - s move from psII to psI where they provide energy for active transport of H + from the stroma into the thylakoid space 5.Pigments in (ps)I absorb light energy which re- excites e - s for NADP + to pick up 6.H + ions move through ATP synthase to make ADP into ATP