Photosynthesis

Question 1

Photosynthetic reaction

Answer 1

Photosynthesis is chemical reaction in which energy is transferred from environment as light from sun to leaves of a plant. Endothermic reaction
Chlorophyll in chloroplast absorbs light energy

Question 2

Photosynthetic reaction: equation

Answer 2

6CO2 + 6H2O → C6H12O6 + 6O2
(Numbers are small)
Carbon dioxide + water → glucose + oxygen

Question 3

Rate of photosynthesis

Answer 3

Limiting factors: temp, carbon dioxide concentration,light intensity, amount of chlorophyll
Less chlorophyll in leaves reduce rate of photosynthesis. More chlorophyll may be produced by plants in well lit areas to increase photosynthesis

Question 4

Limiting factors and photosynthesis rate: temperature

Answer 4

Low temp, rate of photosynthesis low because reactant molecules have less energy
Photosynthesis is enzyme controlled reaction so high temp causes enzyme to denature and rate quickly decreases

Question 5

Limiting factors and photosynthesis rate: carbon dioxide concentration

Answer 5

Carbon dioxide used up in photosynthesis so increasing carbon dioxide increases rate of photosynthesis
At certain point another factor becomes limiting
Carbon dioxide often limiting factor for photosynthesis

Question 6

Limiting factors and photosynthesis rate: light intensity

Answer 6

Light energy needed for photosynthesis so increase light energy increases rate of photosynthesis
At certain point another factor becomes limiting
Photosynthesis will stop if there’s little or no light

Question 7

Interaction of limiting factors

Answer 7

Limiting factors often interact and any one of them may be limiting photosynthesis

Question 8

Inverse square law

Answer 8

As distance it light source from plant increases, light intensity decreases
Called an inverse relationship, not linear as light intensity varies in inverse proportion to the square of the distance

light intensity ⍺ 1/distance²

Question 9

Greenhouse economics

Answer 9

Commercial greenhouses control limiting factors to get the highest possible rates of photosynthesis so they can grow plants as fast as possible or produce the highest yields whilst still making profits

Question 10

Uses of glucose produced in photosynthesis

Answer 10

Convert into insoluble starch for photosynthesis (in leaves, tubers, bulbs)
Produce fat and lipids for storage
Produce amino acids for protein synthesis- plants also need nitrate ions from soil for this
Produce cellulose to strengthen cell walls
For respiration to produce energy