Photosynthesis and limiting factors

Question 1

What does photosynthesis do and where does it take place ?

Answer 1

uses energy to change co2 and water into glucose and oxygen.
Takes place in chloroplast in green plant cells - they contain pigments like chlorophyll that absorbs light

Energy transferred to the chloroplasts from the environment by light

Question 2

Is photosynthesis endo or exo thermic ?

Answer 2

Endothermic - energy is transferred from the environment in the process.

Question 3

Word equation for photosynthesis
Symbol equation for photosynthesis

Answer 3

Carbon Dioxide + Water → (light) Glucose + Oxygen

6CO2 + 6H2O → (light) C6H12O6 + 6O2

Question 4

Plants use glucose in 5 ways

Answer 4

1) For respiration - this transfers energy from glucose which enables the plants to convert the rest of glucose into various other useful substances

2) Making cellulose - glucose converted into cellulose for making strong plant cell walls

3) Making amino acids - Glucose combined with nitrate ions to make amino acids which are then made into proteins

4) stored as oils and fats - Glucose turned into lipids for storing in seeds

5) Stored as starch - glucose turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis is not happening like in winter. Starch is insoluble which makes it much better for storing than glucose. A cell with lots of glucose in would draw in loads of water and swell up

Question 5

What is the rate of photosynthesis affected by ?

Answer 5

• intensity of light
• conc of co2
• temp

ANY of these can become limiting factor - stops photosynthesis from happening faster

These factors have combined effect on the rate of photosynthesis but which factor is limiting at a particular time depends on the environmental conditions.

• At night light is limiting factor
• In winter its often Temp
• when its warm and bright enough the limiting factor is usually amount of co2
• Chlorophyll can also be limiting factor

Question 6

When can the amount of chlorophyll can be affected ?

Answer 6

The amount of chlorophyll can be affected by disease or environmental stress such as lack of nutrients . These factors can cause chloroplast to become damaged or to not make enough chlorophyll . This means the rate of photosynthesis is reduced because they can’t absorb as much light.