Topic 5: photosynthesis, biomass & climate change

How are chloroplasts adapted to photosynthesis?

• contain photosynthetic pigments to absorb photons

• have enzymes for photosynthesis like RuBisCO & ATP synthase

• thylakoids stacked into a grana to increase surface area

• stroma directly surrounds grana so the products of photosynthesis directly diffuse into stroma

Outline cyclic photophosphorylation

• involves PSI

• excited electrons enter the electron transport chain to produce ATP & then returns to PSI

• no reduction of NADP and no water required to replace lost electrons

Outline non-cyclic photophosphorylation

• involved PS I & II

• excited electrons enter the electron transport chain to produce ATP

• NADP acts as a final electron acceptor and is reduced

• water is photolysed to compensate for electrons lost from PSi

Describe the light dependent stage of photosynthesis

1. Photoionization: light energy excites electrons causing them to leave the chlorophyll and pass to an electron acceptor at the start of the ETC. Electrons passes down the ETC.

2. Photophosphorylation: energy released from electrons generates ATP from ADP and inorganic phosphate

3. Photolysis of water: light splits water into H+ & oxygen (by-product) Electrons are used to replace the electrons lost from the chlorophyll in step 1.

4. Chemiosmosis: H+ ions are pumped across the membrane using ATP made in step 2 creating a chemical potential gradient

5. protons pass back through the membrane through ATP synthase enzyme. NADPH formed by joining with e- & H+

Describe the light independent stage of photosynthesis

• Carbon Fixation: CO2 is fixed to ribulose biphosphate (RuBP) (5C) by the enzyme rubisco

• Reduction: the 6C compound intermediate is unstable so it immediately splits into 2 molecules of glycerate-3-phosphate (GP) (3C). GP reduced to triose phosphate (GALP) (3C) by ATP & NADPH

• Regeneration: GALP used to form hexose sugar (ex. glucose) and the rest is used to regenerate RuBP

define absorption spectrum

the absorption spectrum indicates the wavelengths of light absorbed by each pigment

define action spectrum

the action spectrum indicates the overall rate of photosynthesis at each wavelength

What is meant by net & gross primary productivity?

GPP — the rate of chemical energy fixture during photosynthesis by all producers
NPP — the amount of chemical energy that is available to consumers

How is net primary productivity calculate?

NPP=GPP-R

What is distribution?

the spread of living organisms in an ecosystem

Describe 4 pieces of evidence for climate change

• CO2 records

• temp records

• pollen grains from peat bogs

• dendrochronology

What is dendrochronology?

a new tree ring is added each year. Width of ring indicates the temperature and moisture of that year

What is anthropogenic climate change?

changes in weather patterns due to human activities

What is the greenhouse effect?

Infrared radiation from the sun is trapped by greenhouse gases, warming Earth’s surface and atmosphere.

Why do climate change models have limitations?

do not consider factors that may change

State 2 geological effects of climate change

• rainfall patterns change

• season cycles change

How can climate change affect plants and animals?

• distribution of spices & migratory patterns change. many species move north to cooler area. increases interspecific competition

• selection pressure change. natural selection may not occur quickly enough in some populations

• disruption to life cycles and development e. sex of reptiles