Photosynthesis 1 Flashcards
(13 cards)
What is the photosynthesis equation?
6H20 + 6CO2 = C6H12O6 + 6O2
Where does photosynthesis take place?
Chloroplasts
Describe the structure of a chloroplast
Outer membrane
Inner membrane space
Inner membrane
Stroma
Thylakoid membranes
Lamellae
Grana
Thylakoid lumen
What are grana ?
Stacks of thylakoid membranes
What are lamellae ?
They connect the grana
What are carotenoids ?
A photosynthetic pigment
Mainly absorb blue light
What is resonance energy transfer ?
It allows light energy absorbed by pigments to be efficiently passed to chlorophyll a in the reaction centre, where it can then be converted to chemical energy
What is the reaction centre in PS 2 called ?
P680
What is the reaction centre in PS 1 called ?
P700
What is the Z scheme ?
It describes the flow of electrons during the light- dependent reactions of photosynthesis
What is the manganese cluster ?
It is found in PS2 and is essential for splitting water molecules during photosynthesis
What happens to electrons during electron transport?
- Light energy excites an electron in the P680 reaction centre in PSII
- The electron is transferred to pheophytin then to plastaquinone
- The lost electron in P680 is replaced by electrons from water, split by the manganese cluster
- Plastoquinone (PQ) becomes reduced to plastoquinol (PQH₂) and transports electrons to the cytochrome b₆f complex
- This step also pumps protons (H⁺) into the thylakoid lumen
- Electrons are carried by plastocyanin (PC) to Photosystem I (PSI)
- Light excites P700 which energises the electrons
- The excited electrons are transferred through a chain involving ferredoxin (Fd) and finally to NADP⁺ via ferredoxin-NADP⁺ reductase
What is the role of Cytochrome b6f complex ?
- It receives electrons from plastoquinol (PQH₂)
- Electrons are delivered to PSI
- As PQH₂ is oxidized back to plastoquinone (PQ), it releases 2 electrons and 2 protons (H⁺)
- Protons are released into the thylakoid lumen
- This creates a proton difference of 6 across the thylakoid membrane
