Photosynthesis (chpt. 11) Flashcards
Photosynthesis
The process by which plants make food using carbon dioxide and water in the presence of sunlight and chlorophyll
Photosynthesis
The process by which plants make food using carbon dioxide and water in the presence of sunlight and chlorophyll
Chemical formula for photosynthesis
6CO. + 6H. O. Sunlight. C. H. O. + 6O
2. 2. Chlorophyll 6. 12. 6. 2
Word formula for photosynthesis
. .Sunlight
Carbon dioxide + water ——————> glucose + oxygen
Chlorophyll
Why is photosynthesis important
Plants use it to make food
Animals get their food from plants
Produces oxygen
Takes in carbon dioxide from the air
Factors affecting the rate of photosynthesis
Carbon dioxide → external (taken in from atmosphere) internal (small amount produced during respiration of leaf cells
Light → provides energy needed for photosynthesis
Temperature → optimum temperature for plant enzymes is 25 - 30°C
Water → freely available, absorbed by plant root hairs and is conducted through the xylem by the transpiration stream
Light stage - pathway 1
Light is absorbed by chlorophyll and electrons are energised
High energy electrons enter P 1 where they move through electron receptors and lose energy
This energy is trapped by ADP and a phosphate and is used to make ATP and water
Light stage - pathway 2
Electrons move from P 1 to P 2 and do not return to chlorophyll
At the same time, water is split into 4 hydrogen ions, oxygen and 4 electrons (photolysis)
These electrons are passed back to the chlorophyll
Hydrogen ions combine with NADP- to form NADPH
Some hydrogen ions are sent to a proton pool for later use
Oxygen is released into atmosphere or used for internal respiration
Photolysis
The splitting of water by light
Products of the light stage
ATP - supplies energy for dark stage
NADPH - supplies protons and electrons for dark stage
oxygen - used in respiration or released into atmosphere
What is the dark stage
Light independent
Occurs in chloroplast
Enzymes used so is affected by temp
Aka Calvin cycle
Requires products from light stage
Where does the dark stage of photosynthesis take place
Chloroplast
Key stages of dark stage
NADPH releases protons and electrons
Carbon dioxide is reduced to glucose
ATP releases energy and is converted back into ADP
ADP and NADP+ are recycled back to light stage
Products of dark stage
Glucose
NADP
ADP
How can you increase plant production in a greenhouse
Burn gas
Pump in carbon dioxide
Artificial light
When light is absorbed by the chlorophyll, to which specific type of chlorophyll molecule is it passed
Reaction centre
Where in the leaf does the dark stage take place
Chlorophyll/ stroma
Where does the light stage take place
Chlorophyll / grana
What features do pathway 1 and pathway 2 have in common
Formation of ATP
Movement of electrons through carriers
Does chlorophyll absorb green light?
No, leaves are green and therefore green light is reflected
What is the role of electron acceptors in the production of ATP
Energised electrons picked up by electron acceptor
As electrons pass from one acceptor to the next they lose energy
This energy is then used to add a phosphate group to ADP, forming ATP
Importance of photolysis
Produces hydrogen ions, electrons
Used to make NADPH
One factor that could alter rate of the dark phase
Temperature
pH
Role of ATP in dark stage
Provides energy for conversion of carbon dioxide to glucose
