Photosynthesis Flashcards
Photosynthesis definition
a process by which phototrophs convert light energy into chemical energy
Phootsynthesis stages
- Light dependent reaction: Photosystems.
- Light independent reaction: Calvin Cycle.
Phycobiliproteins:
- Chain of pigments that absorb and emit different colours.
- Ends with chlorophyll absorbing red light.
LDR:
- Produces oxygen.
- NADPH and ATP, used in Calvin cycle
LIR:
- Synthesis G3P, able to build more complex organic molecules
C3 plants:
- Only use the calvin cycle.
- 95% of plants.
- Able to photorespire.
C4 plants:
- Minimise photorespiration.
- 1% of plants.
- Separate light (mesophyll) and dark reactions (bundle sheath).
CAM plants:
- In areas of low light.
- Two systems separated by time not by place.
Macroalgae origins
1 billion yrs ago
Seagrass origins
- Earliest seagrass in cretaceous period (~90mya.
- Seagrasses have less evolutionary time to adapt.
Seagrass:
- Only flowering plants in marine environment.
- Grow in large monospecific or mixed meadows.
- Shallow, sheltered soft bottomed environments
- Ecological engineers, influence physical, chemical, and biological environment
what is Seagrass distribution affected by
- Threatened habitat worldwide.
- Distribution affected by temperature, salinity, waves, current, depth, light availability and substrate.
Seagrass as ecological engineers
- Absorb nutrients and slow flow of water, improves clarity, and reduces erosion.
- Act as nutrient pump in low nutrient areas.
Rhizome
horizontal underground plant stem capable of producing the shoot and root systems of a new plant
- important for anchoring and nutrient transfer.
Photosynthesis within seagrass
- High light requirement need 10% surface light.
- Specialized C fixation mechanism, photosynthesis constrained by low carbon dioxide concentrations.
Seagrass, light adaptations:
- Changes in leaf morphology and pigment composition.
- Chlorophyll concentration peaks in deep water in winter.
Seagrass, carbon acquisition adaptations:
- Seagrass habitat is conventionally fully marine.
- Salinity 33+
- pH ~8.2
- HCO3 2mol per m3
- Very little carbon dioxide available, 10mmol per m3 @ 25 degrees.
- Acidification on the environment to alter carbonate chemistry and makes carbon dioxide more available, proton pump.
- Presence of multiple carbonic anhydrase which interconvert carbon dioxide and bicarbonate
Seagrass, blue carbon:
- Seagrass meadows account for >10% oceans total carbon storage.
- Sequestering carbon dioxide through photosynthesis and storing organic carbon underneath soils for millennia.
Why is carbon removal using coastal blue carbon ecosystems is uncertain and unreliable
- High variability in C burial rates.
- Errors in determining C burial rates.
- Lateral carbon transport.
- Fluxes of methane and NO.
- Carbonate formation and dissolution,
- Vulnerability to future climate change.
- Vulnerability to non-climatic factors.
Blue carbon
Biologically driven carbon fluxes and storage in marine systems that are amenable to management.
Types of macroalgae
- Rhodophytes (red), phaeophytes (green and brown), chlorophytes (green).
- Colour is mainly a function of accessory photosynthetic pigments of the light harvesting complex.
Macroalgae, carbon sink:
- Key marine communities in inshore waters, providing essential protection and nursery ground areas for many fish and other species.
- Inshore food webs driven by sea-weed derived carbon.
- Exploited as a food source, and as a source of fertiliser and counteract beach erosion.
- Estimated to sequester at least 10^9 tons of C per year.
Macroalgae, light adaptations:
- Dynamic photoinhibition at high UV to prevent damage from oxygen radicals through excessive photosynthesis.
- Chloroplast rearrangement, controlled by a cryptochrome photoreceptor in brown macroalgae.
- adaptation to low light is also possible, brown kelps continue growth at 0.6-1.2% of surface light, deep-grown red algae can survive at an absolute minimum of 0.001-0.05%.
Kelp, wave exposure adaptations
- Sheltered=strength increasing traits.
- Moderately exposed= go with the flow tactic.
- Very exposed= size-reducing tactic.
Macroalgae, nutrient uptake:
- Fast growing species are successful in eutrophic systems, whilst slow-gorwing species persist in oligotrophic coastal waters.
- Capacity for surge uptake of N species when conditions prevail.
- Under current conditions marine macroalgae are saturated with respect to organic carbon sources.
Climate change vs macroalgae
Seawater is in equilibrium with air contains ca 13microM Carbon dioxide and 2.2mM anionic C, mainly in the form of HCO3.
* Under these conditions, photosynthesis of marine macroalgae is often saturated by the seawater Ci-composition, largely because they can efficiently use HCO3.
Climate change vs seawater
Posses less efficient systems for utilizing HCO3 and their photosynthesis is therefore Ci-limited because of the low concentration and slow diffusive supply of Carbon dioxide to the leaves.
Biomineralization:
- The process by which mineral crystals are deposited in the matrix of living organisms.
- Plays significant global roles in terraforming the planet as well as in biogeochemical cycles and as a carbon sink.
Organomineralization:
- Biologically induced mineralization, metabolic activity of microbes produces chemical conditions favourable for mineral formation.
- chemical conditions surrounding the site of mineral formation are influenced by abiotic processes
Biomineralization, evolution:
- Biomineralized structures evolve and diversify when the energetic cost of biomineral production is less than the expense of producing an equivalent organic structure.
evolutionary evidence for biomineralization
- 1st evidence of biomineralization approx. 750mya.
- Sponge-grade organisms may have formed calcite skeletons 630 mya.
Phosphate uses
- Hydroxyapatite, primary constituent of bone, teeth and fish scales.
Silicate uses
- Diatoms and radiolaria form frustules from hydrated amorphous silica.
- Sponge spicules
Iron minerals uses
- Magnetite or goethite, teeth or radula that are used for scraping.
- Pyrite and gregite uses
- Gastropod molluscs living close to hydrothermal vents reinforce carbonate shells.
Carbonate uses
- Major carbonate is calcium.
- Calcite - coccos, forams.
- Aragonite - corals.
Marine Biogenic calcification:
- More acidic conditions reduce abundance of carbonates.
- When saturation state is high >1 (super saturation) in terms of calcium carbonate, organisms can extract the Ca and CO3 ions from the seawater and form solid crystals of calcium carbonate.
- Lower than 1 is undersaturated so favours dissolution
Calcification, molluscs:
- Specialized proteins are responsible for directing crystal nucleation, phase, morphology, and growth dynamics and ultimately give the shell strength.
- Function: defend soft tissues against parasites by enclosing innards.
Echinoderms calcification
- Intracellular calcification:
- Form large vesicles from fusing of cell membranes, inside these vesicles is where the calcified crystals form.
- endoskeleton enclosed by epidermis
Ocean acidification, corals:
- Low pH, increased skeletal microporosity, decreased net calcification.
Ocean acidification, echinoderms:
- Impedes larval growth, negative relationship between arm length and increasing acidity.
- Larval success may be the bottleneck for species success.
What is the difference between
organomineralization and biomineralization?
Biomineralization = mineral crystals
deposited in the matrix of a living organism.
Organomineralization = mineral deposition
mediated by organic matter independent of
the living organism
Which phase of calcium carbonate (aragonite
or calcite) is more vulnerable under ocean
acidification and why?
Aragonite, because it is
more soluble under low pH conditions.
