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Photosynthesis. Photosynthesis Equation. CO 2 + H 2 O + SUN C 6 H 12 O 6 + O 2. Photosynthesis occurs in the chloroplasts. Structures inside chloroplasts where process of photosynthesis takes place are Thylakoids. Grana – Stacks of thylakoids
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Photosynthesis Equation • CO2 + H2O + SUN C6H12O6 + O2
Structures inside chloroplasts where process of photosynthesis takes place are Thylakoids • Grana – Stacks of thylakoids • Stroma – The fluid surrounding thylakoid
There are 2 basic steps for photosynthesis • 1) Light reactions • 2) Dark reactions (light independent reactions) (or Calvin cycle)
Light reactions convert light energy to chemical energy (ATP & NADPH) • Dark reactions (Calvin Cycle) turn chemical energy into Sugars
Light reactions Occur in the Thylakoid membrane • Have two parts: a) Photosystem II (PSII) b) Photosystem I (PSI)
Photosystem II (comes first) A) Sunlight hits Chlorophyll A and transfers energy to the reaction center (another Chlorophyll molecule)
Photosystem II B) This releases electrons which travel through molecules in the electron transport chain (ETC) ending at PSI PS I PS II
Photosystem II C) An enzyme splits water into protons, electrons and oxygen. This provides more electrons to travel to PSI
Water reaction in PSII 2H20 4 H+ + 4 e- + O2 Protons (H+) Will be used later in PSI Electrons (e-) – Move along ETC to PSI Oxygen (O2) – Released as a gas, NOT needed
Photosystem I (comes 2nd) A) Electrons from ETC reach PSI reaction center in a second molecule of Chlorophyll A
Photosystem I B) Sun helps electrons go through a 2nd Electron transport chain (ETC) in membrane and Causing NADP+ to turn into NADPH
H+ Photosystem I C) ATP synthase pushes protons (H+) out of membrane to make ATP
Reduction of NADPH • NADP+ is reduced by electrons and protons that were produced by the water splitting • NADP+ + e- + H+ NADPH
Formation of ATP The enzyme ATP synthase uses H+ energy to produce ATP ADP + P + Energy ATP
Summary of light reactions • H20 + sunlight + NADP+ + ADP O2 + NADPH + ATP • The energy molecules NADPH and ATP can not be stored for long. • They will be used in Dark reactions to make sugar
Dark reactions (Calvin Cycle) • Occurs in Stroma • Called Light independent reactions • They do not need light, but they need the ATP and NADPH from the light reactions
Calvin Cycle • If there is no light, The Calvin Cycle soon uses up its ATP and NADPH and stops working. • LIKE a car, will drive for a while, but must fill up sometime
Calvin Cycle • The process of using ATP and NADPH energy to join CO2 into sugars
Calvin Cycle Steps (C3 plants) A) Carbon Fixation A molecule of CO2 combines with RuBP(enzyme = Rubisco) then splits into 2 PGA molecules
Calvin Cycle Steps (C3) B) Reduction - ATP and NADPH are used to form GP3, 3 carbon sugar
Calvin Cycle Steps (C3) C) Regeneration of RuBP - 5 of the 6 Carbons reform into RuBP prepare for next CO2
Calvin Cycle Steps (C3) 3 turns of the cycle produce one 3 carbon sugar. 6 turns forms 1 glucose
Summary of Dark Reactions • CO2 + NADPH + ATP Sugar + NADP+ + ADP + P
The dark reactions are called the light dependant reactions because they depend on the ATP and NADPH produced in the light reactions