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Photosynthesis (The light reactions convert solar energy to the chemical…
Photosynthesis
The light reactions convert solar energy to the chemical energy of ATP and NADPH
Photosynthetic pigments: the light recepters
Chlorophyll a (直接參與光反應)
Chlorophyll b (輔助色素)
caroenoids類胡蘿蔔素(輔助色素)
更重要的功能：photoprotection光保護作用(吸收及驅散過量光能)
Excitation of chlorophyll by light
The nature of sunlight
Light is electromagnetic energy(radiation)
A photosystem: a reaction-center complex associated with light-harvesting complexes
Light-harvesting complexe
protein combined with lots of pigments(chlorophyll a, chlorophyll b, caroenoid)
capture the light and transport to the reaction-center complex
Reaction-center complex
a pair of specific chlorophyll a
receive the light and capture the electrons from the H2O
primary electron acceptor
capture the electron from a pair of specific chlorophyll a
Photosystem Ⅱ (P680)
Photosystem Ⅰ (P700)
Linear electron flow
當光子碰撞到光能捕獲複合體色素分子，色素的其中一個電子會被激發，當回到基態時，會促使鄰近色素分子的其中之一個電子同步被提升至激態，直到傳送到第二光系統的葉綠素a(P680)
電子被激活的P680移轉給初級電子接受者(P680 → P680+)
酵素催化水裂解，P680+從中得到一個電子填補空缺
電子傳遞鏈：色素體醌(plastoquinone, Pq)、細胞色素複合體、細胞色素藍素(plastocyanin, Pc)
當電子向下傳遞釋出能量可供製造ATP；電子通過細胞色素複合體時，質子唧越建立化學滲透作用的質子梯度
電子傳遞給P700+填補空缺，並傳遞至初級接受者
氧鐵化還原蛋白(ferredoxin, Fd)，此ETC不會造就質子梯度，因此無ATP產生
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Cyclic electron flow
發生在光系統Ⅰ(P700)，電子由Fd回到細胞色素複合體，不會產生NADPH，但會生成ATP
The Calvin cycle uses ATP&NADPH to convert CO2 to sugar
Phase 2: 還原作用
每一分子的3-磷酸甘油酸接受自ATP的一個磷酸基形成1, 3-雙磷酸甘油酸；NADPH提供一對電子，使之失去一個磷酸基，形成甘油酸-3-磷酸(G3P)
3
CO2得6
G3P，但僅淨得1
G3P，其餘5
G3P生成3*RuBP
Phase 3: CO2接受者(RuBP)的再生
5
G3P需3ATP再生成3
RuBP，重新接受CO2
Phase 1: 固碳作用
RUBP羧化酶(RuBP carboxylase, rubisco)將每一個CO2併入核酮糖雙磷酸(ribulose bisphosphate, RuBP)五碳糖上，產生六碳的中間產物，並迅速分解為兩個3-磷酸甘油酸(3-phosphoglycerate)
就每一個G3P淨合成，需9ATP和6NADPH
Photosynthesis converts light energy to the chemical energy of food
Chloroplasts: the sites of photosynthesis in plants
Stroma 基質
Granum 葉綠餅(pl. grana)
Inner membrane 內膜
Thylakoid 類囊體
intermembrane space 膜間腔
Thylakoid space 類囊體腔
Outer membrane 外膜
chlorophyll 葉綠素
Tracking atoms through photosynthesis: scientific inquiry
Photosynthesis as a redox process
The two stages of photosynthesis: a preview
Light reactions
(electron recepter) NADP+ → NADPH
take place in thylakoid membranes
ADP → ATP (photophosphorylation 光磷酸化反應)
Calvin cycle
aka. Dark reactions
aka. Light-in-dependent reactions 光非依賴型反應
carbon fixation
by the help of NADPH → NADP+
by the help of ATP → ADP
take place in stroma
The splitting of water
氧氣的產生來自水的裂解