4.4.1.1 Photosynthetic reaction/ uses of glucose

what is photosynthesis

the process by which plants make glucose from sunlight.

it is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light

word equation for photosynthesis

carbon dioxide + water →(light) glucose+ oxygen

symbol equation for photosynthesis

CO₂ + H2O → C₆H₁₂O₆ + O₂

limiting factors affecting the rate of photosynthesis

light intensity

temperature

carbon dioxide levels

amount of chlorophyll

light intensity

increasing light intensity increases rate, if light intensity keeps on increasing, therefore light intensity is the limiting factor at this point

rate of photosynthesis no longer increases and levels off therefore light intensity is no longer the limiting factor and something else is now in short supply

carbon dioxide

increasing carbon dioxide increases rate, if carbon dioxide keeps on increasing, therefore carbon dioxide concentration is the limiting factor at this point

rate of photosynthesis no longer increases and levels off therefore light intensity is no longer the limiting factor and something else is now in short supply

chlorophyll

if chloroplast is damaged or not enough rate of psis is reduced as it cannot trap as much light

temperature

increasing temperature, enzymes involved in photosynthesis work faster so the rate increases, therefore temperature is the limiting factor at this point

after optimum temperature if it keeps on increasing enzymes will denature and the rate of psis falls

equation for light intensity

inverse square law

light intensity - 1/ distance²

what is a limiting factor

environmental conditions which in low levels restricts any increase of the rate of photosynthesis

seen by the graph levelling off

The glucose produced in photosynthesis may be used for

1. used for respiration
2. converted into insoluble starch for storage- so it can be used when needed ie night or winter
3. used to produce fat or oil for storage
4. used to produce cellulose, which strengthens the cell wall
5. used to produce amino acids for protein synthesis- do this by absorbing nitrate ions from the soil

farmers use of limiting factors

farmers want to increase the rate of photosynthesis as this increases the yield of crops they produce

to do this farmers light and heat greenhouse gases, they also add extra CO₂

however it is expensive therefore, the extra cost has to be justified by increasing yield

some Gardners use oil burners as this increases heat and CO₂ at the same time