Photosynthesis Flashcards
O2 Rich Atmosphere Resulted In (3)
Increase in respiration efficiency (aerobic)
Biosynthesis of sterols (membrane flexibility and endosymbiosis)
Formation of the stratospheric ozone layer (protect from UV and move to land)
Light Reaction Location
Thylakoid membrane
(energy transduction reactions)
Dark Reaction Location
Stroma
(carbon fixation)
Phycobilins
Occur in cyanobacteria and red algae
Accessory pigment that broadens the range
Photosystem II purpose
Splitting of water
Photosystem I purpose
Creation of NADPH
Algal Challenges for Photosynthesis (3)
Coping with light variation and high light
Utilizing CO2 in modern habitats (higher CO2 prehistorically)
Acquiring limiting nutrients
Quality of light
Depth dependent
Blue Deeper
Red shallower
Quantity of light
Intensity of light
water clarity dependent
more penetration in deep water
Algal Solutions to Light Acquisition (3)
Phototaxis: flagellate cells use light detectors to move to light
Accessory Pigments: Harvest light at wavelengths not accepted by chlorophyll a, and prevent UV damage
Mixotrophic Feeding: Absorb organic molecules or feed
The problem of the Modern World
CO2 was higher, O2 lower 2.2 billion years ago when algae evolved
CO2 diffuses 10 000 times slower in water
High CO2 required for Calvin cycle
Solution of Modern World
Invade terrestrial habitats
Evolution of different forms of Rubisco
Evolution of CCMs (carbon concentration mechanisms)
Rubisco (RuBP)
Catalyzes C fixation
Convert CO2 into reduced organic compounds
When O2 is high, works as an oxygenase
Rubisco evolved to avoid photorespiration
High O2 outcompete CO2 in light reactions, results in loss of organic C
Rubisco Evolution (2)
Specificity: Ratio of Rubisco selectivity of CO2 over O2 (Red algae has high selectivity)
Kcat: Rate of Rubisco turnover (cyanobacteria have high Kcat)
A tradeoff between these modes
