Topic 6: Phototrophic Metabolism Flashcards
What happens in the formation of glucose and O2 from CO2 and H2O?
- CO2 is reduced to form glucose
- H2O is oxidized to form O2
- Polar covalent bonds in reactants are broken
- Non-polar covalent bonds in the products are formed
What are the membranes in the Chloroplast?
- Outer membrane
- Inner membrane
- Thylakoid
What are the two important spaces in the Chloroplast?
- Stroma
- Thylakoid lumen
What does the photosynthetic process consist of?
- Light reaction (transforming solar energy into chemical energy)
- Dark reaction (use chemical energy to fix CO2 into carbohydrates)
What are the similarities between Photosynthesis and Cellular Respiration? (3 things)
- ATP Synthase
- Both use proton gradient
- Electron taxis
What are the differences between Photosynthesis and Cellular Respiration? (1 thing)
- Not happening spontaneously in photosynthesis, needs energy from the sun
Relationship between associated with light and wavelength
Inversely proportional
When a photon strikes an object, it can be…
- Reflected (bounced back)
- Transmitted (passed right through the object)
- Absorbed (absorbed by electrons which gain energy from the photon)
Pigments absorb photons of specific wavelengths under what conditions?
The wavelength must exactly match the energy needed to raise an electron to a higher energy level
When a photon is absorbed by an electron what happens?
It becomes excited and moves from a low-energy level to a high-energy level
What are embedded into the thylakoid membrane?
Photosynthetic pigments
What are Chlorophylls?
The main pigment in most photoautotrophs
Carotenoids act as…
Accessory pigments
What are photosystems?
Complexes with proteins where pigment molecules are organized (light-harvesting complexes)
Where are hundreds of antenna pigments grouped?
Grouped around a reaction centre
What happens when antenna pigments are excited?
Channel energy to the reaction centre (inductive resonance)
- “players passing (antenna) a basketball to the net (reaction centre) “
What is a reaction centre?
A collection of proteins that interact with pigments
What is Inductive Resonance?
The transfer of energy from one electron to another
How do Reaction centres reduce a Primary Electron Acceptor?
- Light is absorbed by an antenna pigment
- Energy is transferred by inductive resonance to a reaction centre
- The reaction centre donates an electron to a primary electron acceptor (PEA)
What does photosystem II do?
- Absorb energy from photons
- P680 (in its reduced form), the electron gets excited
- P680+ donates excited electron to PEA
- P680+ (in its oxidized form), accepts an electron donated by water (which is oxidized)
- Returns to P680 (in its reduced form)
What do a low [H+] and a high [H+] mean for pH?
Low [H+] = higher pH
High [H+] = lower pH
How does Photosystem II produce PMF?
- P680 reduces its PEA, which passes the electron to PQ (plastoquinone)
- PQ is a hydrophobic electron taxi, that grabs a proton from the stroma when reduced
- PQ reduces cytochrome complex and releases a proton into the lumen
- Cytochrome reduces plastocyanin that passes electron to P700+
What does Photosystem I do?
- P700 absorbs energy from the sun
- P700 (reduced form), the electron gets excited
- P700+ donates excited electrons to the PEA
- P700+ (oxidized form), gains an electron from plastocyanin which is oxidized)
- Returns to P700 (reduced form)
How does Photosystem I produce NADPH
- P700 reduced PEA, which passes electrons to ferredoxin
- Ferredoxin (an electron taxi) in the stroma reduces NADP+ reductase
- NADP+ reductase reduces NADP+ to NADPH in the stroma
*P700, replaces its electrons by accepting electrons from plastocyanin
