Sunday, 4 September y
Energy Transfers In & Between Organisms
Photosynthesis
Light dependent reaction
Factors affecting photosynthesis
Why does light intensity effect the rate of photosynthesis
- light energy needed for photoionisation (these electrons move down ETC - energy
used to join ADP +Pi > ATP)
- light energy need for photolysis - split water into hydrogen ions, electrons and oxygen
- NADPH is reduced by the electrons and hydrogen
- if LDR cannot occur then not ATP/NADPH is passed to the LIR
How can increased temps effect growth of plants
- increases it if there is enough photosynthesis
- IF there is cloud cover etc will be decreased growth
- Rate of respiration will increase at higher temps
- rate of photosynthesis will be limited - for growth to occur there must be more photo-
synthesis than respiration
Protons role in the LDR
- formed by photolysis
- build up in thylakoid space
- pass out to stroma by ATP synthase
- this forms ATP from ADP + Pi
- protons reduce NADP to NADPH
Chemicals that effect proteins
e.g. weedkillers
- will reduce growth
- less electrons passed down ETC
- less protons passed across thylakoid membrane (not enough energy for active trans-
port) - so there is less of a concentration gradient
- Less protons move down ATP synthase so less ATP produced
- less NADPH produced as less electrons passed down ETC to reduce it
1
, Sunday, 4 September y
- so there is less ATP and NADPH for the LIR
- less photosynthesis - less sugars produced
Animals living at the bottom of the sea don't have access to light - have to make
their own food using energy stored in chemicals e.g.
- use hydrogen sulphide as a source of protons and electrons (needed as photoionisa-
tion and photolysis cannot occur)
- so that reducing reactions can be carried out
- source of electrons for the ETC
Light independent reaction
Produces of the LIR
- Hexose sugars
- amino acids - protein synthesis
- Lipids - cell membranes / waxy cuticle
- ADP/NADP - used in LDR
Hexose sugar uses
- converted to starch for storage
- converted to sucrose for transport around the plant
- Converted to cellulose for cell walls
- glucose used in respiration to produce ATP
How does the LIR allows for continuous sugar production
- RuBP combines with CO2
- Forms 2 3-carbon molecules - GP
- this is reduced to 2 molecules of 3 carbon TP (using ATP and NADPH)
- one molecule of carbon is lost from
each TP (Adds up to 6 carbon
sugar)
- all the RuBP is regenerated
In the dark
2
Energy Transfers In & Between Organisms
Photosynthesis
Light dependent reaction
Factors affecting photosynthesis
Why does light intensity effect the rate of photosynthesis
- light energy needed for photoionisation (these electrons move down ETC - energy
used to join ADP +Pi > ATP)
- light energy need for photolysis - split water into hydrogen ions, electrons and oxygen
- NADPH is reduced by the electrons and hydrogen
- if LDR cannot occur then not ATP/NADPH is passed to the LIR
How can increased temps effect growth of plants
- increases it if there is enough photosynthesis
- IF there is cloud cover etc will be decreased growth
- Rate of respiration will increase at higher temps
- rate of photosynthesis will be limited - for growth to occur there must be more photo-
synthesis than respiration
Protons role in the LDR
- formed by photolysis
- build up in thylakoid space
- pass out to stroma by ATP synthase
- this forms ATP from ADP + Pi
- protons reduce NADP to NADPH
Chemicals that effect proteins
e.g. weedkillers
- will reduce growth
- less electrons passed down ETC
- less protons passed across thylakoid membrane (not enough energy for active trans-
port) - so there is less of a concentration gradient
- Less protons move down ATP synthase so less ATP produced
- less NADPH produced as less electrons passed down ETC to reduce it
1
, Sunday, 4 September y
- so there is less ATP and NADPH for the LIR
- less photosynthesis - less sugars produced
Animals living at the bottom of the sea don't have access to light - have to make
their own food using energy stored in chemicals e.g.
- use hydrogen sulphide as a source of protons and electrons (needed as photoionisa-
tion and photolysis cannot occur)
- so that reducing reactions can be carried out
- source of electrons for the ETC
Light independent reaction
Produces of the LIR
- Hexose sugars
- amino acids - protein synthesis
- Lipids - cell membranes / waxy cuticle
- ADP/NADP - used in LDR
Hexose sugar uses
- converted to starch for storage
- converted to sucrose for transport around the plant
- Converted to cellulose for cell walls
- glucose used in respiration to produce ATP
How does the LIR allows for continuous sugar production
- RuBP combines with CO2
- Forms 2 3-carbon molecules - GP
- this is reduced to 2 molecules of 3 carbon TP (using ATP and NADPH)
- one molecule of carbon is lost from
each TP (Adds up to 6 carbon
sugar)
- all the RuBP is regenerated
In the dark
2
