11. photosynthesis Flashcards
Symbol equation for photosynthesis
6H20 + 6CO2 = C6H12O6 + 6O2
what is an autotroph
photosynthetic plants that gain all its chemical energy on its own
give 4 adaptations of leaves (for photosynthesis)
large SA
overlapping leaves
thin, shot diffusion pathway
transparent cuticle
stomata
Describe the structure of chloroplasts
the grana, stacks of disc-like structures called thylakoids, the site of light dependant stage of photosynthesis.
stroma, fluid matrix where light independent stage takes place. starch is found here.
What process provides energy for proton pumps? (light dependant)
energy from ‘exited electrons’ in transport proteins
What are the three key stages the light dependant reaction?
- Photolysis
- Photoionisation of chlorophyll
- Chemiosmosis
- Production of ATP and reduced NADP
How are thylakoid membranes adapted for photosynthesis
- large surface area
- precise arrangement of proteins
- chloroplasts have DNA + ribosomes so they can manufacture proteins involved in the light-dependant reaction.
Summarise the light independent stage of photosynthesis (calvin cycle)
- Rubp (5c sugar) undergoes carbon fixation (introduction of C from CO2) catalysed by rubisco
- GP, 3c sugar is reduced by ATP and NADPH (=NADP + ADP)
- 1 TP goes to make glucose
- 5 TP are regnarated into Rubp, requiring ATP.
where does light dependant stage take place?
stroma of chloroplasts
What happens to triose phosphate after the calvin cycle?
- some used to regenerate RuBP
- some converted into organic substances
What enzyme catalyses carbon-fixation of RuBp?
rubisco
What is the site of light independent stage? (photosynthesis)
stroma of chlorolplasts
What can be found in the stroma? (4)
- thylakoids/grana
- 70s ribosomes
- a loop of DNA
- starch grains/sugars
Photolysis of water.
Light energy is absorbed by chlorophyll and splits water into H+ and e-
H20 = (1/2 O2) + 2e- + 2H+
What happens to H+ ions produced in photolysis of water?
Reduces NADP into NADPH, used in LIR
What happens to electrons produced in photolysis of water?
Passed along electron carrier leading to photoionisation.
Photoionisation of the chlorophyll.
- Light energy is absorbed by chlorophyll,
- Energy ‘excites’ electrons in chlorophyll,
- Up an energy level, leaving chlorophyll
- Energy from released electrons used in chemiosmosis.
Summarize chemiosmosis
- Electrons that moved up energy level move along series of proteins in thylakoid membrane
- … releasing energy as they move
- Energy is used to pump protons across chloroplast membranes into thylakoid lumen
- Electrochemical gradient is created, H+ ions diffuse back to stroma through ATP synthase, resulting in production of ATP.
- co-enzyme NADP becomes reduced by H+ ions
During chemiosmosis, where proton pumps on the thylakoid membrane get energy from?
From ‘exited’ electrons as they move along series of proteins.
Three key processes in the calvin cycle.
- Carbon fixation of RuBp ( catalysed by rubisco)
- Reduction of GP to TP (NADPH and ATP needed)
- Regeneration of TP into RuBp (ATP required)
Give three limiting factors of photosynthesis.
light intensity
CO2 concentration
Temperature
How might agricultural practises remove limiting factors?
artificial lighting
heating
burning fuels, releasing CO2
