Photosynthesis (Plant Nutrition) Flashcards
Define photosynthesis
- process where light energy is converted into chemical energy
- chemical energy used to synthesise carbohydrates
- water and CO2 (raw materials)
- oxygen released
Stages of photosynthesis
- Light dependent
2. Light independent
Light dependent
- light energy converted to chemical energy
- light energy used in photolysis of water, split water molecules into oxygen and hydrogen
Light independent
- hydrogen from photolysis used to reduce CO2 to glucose (first stable form of carbohydrate)
- chemical energy frm light dependent stage used in this process
- some enzymes involved
Light dependent stage (Equation)
- 12 molecules of water split to yield 6 molecules of O2 and 24 atoms of hydrogen
- all O2 released during photosynthesis comes from water
- vol of oxygen hence indicates rate of photosynthesis
Light independent stage (equation)
- hydrogen used to reduce 6 molecules of carbon dioxide
- 1 molecule of glucose formed
Overall equation
6 CO2 + 6H2O –> C6H12O6 + 6O2 (light energy & chlorophyll needed)
Conditions essential for photosynthesis
- sunlight
- carbon dioxide
- chlorophyll
- suitable temp (enzyme rxns)
- water
Limiting factors of photosynthesis
- light intensity
- conc of CO2
- temp
What happens to glucose formed during photosynthesis
- Used immediately
- Stored as starch
- Converted to sucrose
- Form proteins
- Fats
Glucose used immediately in leaves
- cellular respiration
- provide energy for cellular activities
- form cellulose cell walls
Stored as starch in leaves
- daylight: rate of photosynthesis v great, sugars formed faster than removed
- excess glucose converted into starch
- darkness: photosynthesis stops, starch converted by enzymes back into glucose
Converted to sucrose
- transported to other parts of plat or storage organs (seeds, stem/root tubers)
- via phloem
- converted to starch, other forms of storage compounds @ storage organs
- might be converted to glucose
Glucose forms proteins
- reacts with nitrates and mineral salts absorbed from soil
- form amino acids in leaves
- used to form proteins
- used in synthesis of new protoplasm in leaves
- excess aa transported to other parts for synthesis of new protoplasm, storage as proteins
Glucose converted to fats
- for storage
- cellular respiration
- synthesis of new protoplasm
Importance of photosynthesis
- Makes chemical energy available to animals and organisms
- Removes CO2, provides O2
- Energy is stored in fossil fuels thru photosynthesis
Photosynthesis makes chemical energy available to animals and other organisms
- sunlight: ultimate source of energy for living organisms
- P: converts light energy to chemical energy
- stored in carbohydrate molecules
- fats, proteins, other organic compounds can be formed from carbo
- these substance eventually become food of other organisms
- producers in food chain
- directly/indirectly obtain food frm plants
Photosynthesis removes CO2 and provides O2
- oxygen released used by living organisms respiration
- release energy for cellular activities
- purifies air
- maintains constant lvl of O2 an CO2 in air
Energy is stored in fossil fuels through photosynthesis
- all energy is fossil fuels ie. coal, gas, oik
- come frm sun, captured by photosynthesis
- burning of fossil fuels releases energy
- daily lives ie. cooking, electricity
