Module 8 (Photosynthesis) Flashcards
What is photosynthesis?
The conversion of light energy to chemical energy
What is the energy yield of photosynthesis in the form of carbohydrates?
4% of light energy is converted into carbohydrates
Photic zone
The area in the ocean where photosynthesis can still occur
Two stages of photosynthesis
- Light capture
- Carbon fixation
Reduction in photosynthesis
CO2 is reduced to form carbohydrate molecules
Oxidation in photosynthesis
Water is oxidized to form oxygen and hydrogen ions, electrons are taken in
Thylakoid
Flattened membrane sacs in the chloroplast
Lumen
Space inside the thylakoid membrane (fluid filled)
Grana
Orderly stacks of thylakoids
Stroma
Space surrounding thylakoids
(location of carbon fixation)
Light dependent reactions
Sunlight energy converted into chemical energy, produces ATP and NADPH
Light -independent reaction
ATP and NADPH used to synthesize carbohydrates (occurs in stroma)
How is light absorbed?
When photons are absorbed, the compound is converted to a higher-energy state, transfers energy to another molecule
Chromophore
Chemical group capable of absorbing light of wavelengths
Why are plants green?
Because the pigment chlorophyll isn’t good at absorbing green wavelengths of light (absorbs red and blue)
Parts of chlorophyll
Porphyrin ring (light absorption)
Phytol side chain (side chain with hydrophobic properties, for inserting chlorophyll into thylakoid membrane)
Accessory pigments
Found in thylakoid membrane, absorb light from regions of the visible spectrum that are poorly absorbed by chlorophyll
Reaction center
A pair of chlorophyll molecules that receives the passed energy (NOT ELECTRONS)
Electron acceptor
Reaction center chlorophyll passes an electron to an electron acceptor
Photosystem II is also known as…
PSII
Photosystem I is also known as…
PSI
Photosynthetic electron transport chain
Drives the formation of ATP and NADPH
Z scheme
Energy trajectory of photosynthetic electron transport
Flow of electrons (in photosynthesis)
H2O->PSII->PSI->NADP+
Proton gradient in photosynthesis
Created as electrons flow along Z pathway
- High in lumen, low in stroma
ATP produced in the chloroplast…
Stays in the chloroplast
Plastoquinone
Carries electrons from PSII to cytochrome b6f complex
Plastocyanin
Carries electrons from the cytochrome b6f complex to PSI by diffusing through the thylakoid lumen
Cytochrome b6f complex
Protein that electrons pass through between PSII and PSI
NADP+ reductase
Takes the electron from the photosynthetic transport chain and converts NADP+ to NADPH
Purpose of Calvin Cycle
Takes a low potential energy carbon compound (CO2) and converts it into a higher-energy carbon compound
Three steps of calvin cycle
Carboxylation, Reduction, Regeneration
Carboxylation
First step of carbon fixation
- CO2 is reacted with RuBP to form a 6 carbon molecule (catalyzed by rubisco), which is then broken down into two PGA molecules (3C)
Reduction
Carbon Fixation
PGA is phosphorylated by ATP to produce triose phosphates, which are then reduced by NADPH and only one can leave the calvin cycle
RuBP
Ribulose 1,5-bisphosphate
Regeneration
Five triose phosphate molecules are used to regenerate RuBP using the input of ATP, produces three RuBP to be used in carboxylation
Excess carbohydrates in a plant produced from the calvin cycle is converted into storage….
As starch
Two possible possibilities of evolution to produce two photosystems
Horizontal gene transfer and gene duplication (and divergence)
Horizontal gene transfer
Passing along genetic information from one cyanobacterium to another
Gene duplication and divergence
PSII duplicates and then diverges (one becomes PSI)
