Photosynthesis

Question 1

Photosynthesis definition

Answer 1

a process by which phototrophs convert light energy into chemical energy

Question 2

Phootsynthesis stages

Answer 2

• Light dependent reaction: Photosystems.
• Light independent reaction: Calvin Cycle.

Question 3

Phycobiliproteins:

Answer 3

• Chain of pigments that absorb and emit different colours.
• Ends with chlorophyll absorbing red light.

Question 4

LDR:

Answer 4

• Produces oxygen.
• NADPH and ATP, used in Calvin cycle

Question 5

LIR:

Answer 5

• Synthesis G3P, able to build more complex organic molecules

Question 6

C3 plants:

Answer 6

• Only use the calvin cycle.
• 95% of plants.
• Able to photorespire.

Question 7

C4 plants:

Answer 7

• Minimise photorespiration.
• 1% of plants.
• Separate light (mesophyll) and dark reactions (bundle sheath).

Question 8

CAM plants:

Answer 8

• In areas of low light.
• Two systems separated by time not by place.

Question 9

Macroalgae origins

Answer 9

1 billion yrs ago

Question 10

Seagrass origins

Answer 10

• Earliest seagrass in cretaceous period (~90mya.
• Seagrasses have less evolutionary time to adapt.

Question 11

Seagrass:

Answer 11

• 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

Question 12

what is Seagrass distribution affected by

Answer 12

• Threatened habitat worldwide.
• Distribution affected by temperature, salinity, waves, current, depth, light availability and substrate.

Question 13

Seagrass as ecological engineers

Answer 13

• Absorb nutrients and slow flow of water, improves clarity, and reduces erosion.
• Act as nutrient pump in low nutrient areas.

Question 14

Rhizome

Answer 14

horizontal underground plant stem capable of producing the shoot and root systems of a new plant
- important for anchoring and nutrient transfer.

Question 15

Photosynthesis within seagrass

Answer 15

• High light requirement need 10% surface light.
• Specialized C fixation mechanism, photosynthesis constrained by low carbon dioxide concentrations.

Question 16

Seagrass, light adaptations:

Answer 16

• Changes in leaf morphology and pigment composition.
• Chlorophyll concentration peaks in deep water in winter.

Question 17

Seagrass, carbon acquisition adaptations:

Answer 17

• 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

Question 18

Seagrass, blue carbon:

Answer 18

• Seagrass meadows account for >10% oceans total carbon storage.
• Sequestering carbon dioxide through photosynthesis and storing organic carbon underneath soils for millennia.

Question 19

Why is carbon removal using coastal blue carbon ecosystems is uncertain and unreliable

Answer 19

• 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.

Question 20

Blue carbon

Answer 20

Biologically driven carbon fluxes and storage in marine systems that are amenable to management.

Question 21

Types of macroalgae

Answer 21

• Rhodophytes (red), phaeophytes (green and brown), chlorophytes (green).
• Colour is mainly a function of accessory photosynthetic pigments of the light harvesting complex.

Question 22

Macroalgae, carbon sink:

Answer 22

• 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.

Question 23

Macroalgae, light adaptations:

Answer 23

• 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%.

Question 24

Kelp, wave exposure adaptations

Answer 24

• Sheltered=strength increasing traits.
• Moderately exposed= go with the flow tactic.
• Very exposed= size-reducing tactic.

Question 25

Macroalgae, nutrient uptake:

Answer 25

• 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.

Question 26

Climate change vs macroalgae

Answer 26

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.

Question 27

Climate change vs seawater

Answer 27

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.

Question 28

Biomineralization:

Answer 28

• 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.

Question 29

Organomineralization:

Answer 29

• 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

Question 30

Biomineralization, evolution:

Answer 30

• Biomineralized structures evolve and diversify when the energetic cost of biomineral production is less than the expense of producing an equivalent organic structure.

Question 31

evolutionary evidence for biomineralization

Answer 31

• 1st evidence of biomineralization approx. 750mya.
• Sponge-grade organisms may have formed calcite skeletons 630 mya.

Question 32

Phosphate uses

Answer 32

• Hydroxyapatite, primary constituent of bone, teeth and fish scales.

Question 33

Silicate uses

Answer 33

• Diatoms and radiolaria form frustules from hydrated amorphous silica.
• Sponge spicules

Question 34

Iron minerals uses

Answer 34

• Magnetite or goethite, teeth or radula that are used for scraping.

Question 35

• Pyrite and gregite uses

Answer 35

• Gastropod molluscs living close to hydrothermal vents reinforce carbonate shells.

Question 36

Carbonate uses

Answer 36

• Major carbonate is calcium.
• Calcite - coccos, forams.
• Aragonite - corals.

Question 37

Marine Biogenic calcification:

Answer 37

• 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

Question 38

Calcification, molluscs:

Answer 38

• 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.

Question 39

Echinoderms calcification

Answer 39

• Intracellular calcification:
• Form large vesicles from fusing of cell membranes, inside these vesicles is where the calcified crystals form.
• endoskeleton enclosed by epidermis

Question 40

Ocean acidification, corals:

Answer 40

• Low pH, increased skeletal microporosity, decreased net calcification.

Question 41

Ocean acidification, echinoderms:

Answer 41

• Impedes larval growth, negative relationship between arm length and increasing acidity.
• Larval success may be the bottleneck for species success.

Question 42

What is the difference between
organomineralization and biomineralization?

Answer 42

Biomineralization = mineral crystals
deposited in the matrix of a living organism.

Organomineralization = mineral deposition
mediated by organic matter independent of
the living organism

Question 43

Which phase of calcium carbonate (aragonite
or calcite) is more vulnerable under ocean
acidification and why?

Answer 43

Aragonite, because it is
more soluble under low pH conditions.