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Flashcards in Photosynthesis Deck (27):

Raw materials required

- Carbon dioxide from air
- Water from soil
- Radiant energy from sun
- Chlorophyll in chloroplasts
- Enzymes


Products of PS

- Glucose which us stored in plant as starch.
- Oxygen which is released into air.


Word equation for PS

carbon dioxide + water -------------> glucose + oxygen


Place where it takes place

Take places in chloroplasts of plant cells.


Light dependent phase

takes place in the presence of light


Light independent phase

can take place in light or darkness


Glucose chemical

C6 H12 O6


Where does light phase take place ?

in the grana of chloroplasts



Water molecules are split into energy rich hydrogen atoms (transferred to light indep phase) and oxygen atoms (released into air as gas)


Light phase process

Radiant energy from sun is absorbed by chlorphyll molecules in thylakoids. Energy transformation takes place and radiant energy is turned into chemical energy. Photolysis occurs and then the energy carrier ATP is formed and is used again for light indep phase.


Where does light independent phase take place ?

in the stroma of chloroplasts


Process of light independent phase

Carbon dioxide absorbed from air combines w hydrogen atoms from light dep phase using energy released from ATP (from in light dep phase)

Glucose is formed. Excess glucose is converted to starch for storage.


Importance of Photosynthesis

- Keeps oxygen and CO2 concentration constant in air and water. Oxygen is needed by organisms for cell respiration. CO2 released in respiration is absorbed by plants during PS.
- Provides food for heterotrophic organisms as fast and proteins are also made glucose and starch produced.
- Makes chemical energy available for cell function.


Factors that influence rate of PS

- light intensity
- temperature
- Carbon dioxide concentration


Light intensity's influence

- increased light = increased PS, but only to a maximum level
- if light intensity becomes too high, stomata close and CO2 then becomes a limiting factor.


Temperatures influence

- Plants photosynthesize optimally at 25°C
- Too high or too low temps can inhibit PS rate.
- Low temp - inactive enzymes
- High temp - denatured enzymes
- At high environmental temps, stomata close to prevent water loss and CO2 becomes a limiting factor.


Carbon dioxides influence

- Decreased CO2 = Decreased PS
- Increased CO2 = increased PS
only to a maximum level as too much CO2 will make the environment acidic.


Energy carrier molecules

Cells use energy carrier molecules to transfer energy from one place to another.
e.g.) ADP & ATP



ADP is converted to its high energy form ATP.


What is a greenhouse ?

A structure w a glass or plastic roof and/or walls where plants are cultivated.


How a greenhouse works ?

Air becomes fairly warm inside the greenhouse, bc sun heats up the air, soil, plants and other objects within the structure. Warm air is trapped therein.


Aim of greenhouse

To provide optimal conditions of light, temp, and CO2 for maximum growth of cultivated plants.


Role of optimum light

- Accelerates PS and stimulates plant growth rate

- Greenhouse must be designed to allow max amount of light to reach plants. Photometer measures light intensity. If amount of light required by a certain plant must change, adaptations to the roof transparency must be made.


Role of optimum temperature

- Must be possible to regulate air temperature in the greenhouse to keep it at an optimum temp for max growth of specific types of plants.
- If temp is too low, it can be increased by heating devices.
- Temps that are too high can be decreased by improving ventilation and having larger door openings. Heating can then be lost.


Role of CO2 enrichment

- A plants PS and growth rate and quality can be increased by increasing CO2 levels in air surrounding plant.
- During the day CO2 levels can increase greatly.
- CO2 enrichment can occur on a large scale by pumping CO2 gas from tanks into greenhouses.


Ways to increase CO2 levels

- Adding sodium bicarbonate to soil
- Adding organic materials to the soil
- Decomposition bacteria in the soil will become more active.


Destarching the plant

Destarch plants beforehand to ensure all starch produced is as a result of the investigation. Keep plant in the dark for 24 to 48 hours (e.g. cupboard, box, tinfoil over the leaf)