Photosynthesis (Plant Nutrition)

Question 1

Define photosynthesis

Answer 1

• process where light energy is converted into chemical energy
• chemical energy used to synthesise carbohydrates
• water and CO2 (raw materials)
• oxygen released

Question 2

Stages of photosynthesis

Answer 2

1. Light dependent

2. Light independent

Question 3

Light dependent

Answer 3

• light energy converted to chemical energy

- light energy used in photolysis of water, split water molecules into oxygen and hydrogen

Question 4

Light independent

Answer 4

• 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

Question 5

Light dependent stage (Equation)

Answer 5

• 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

Question 6

Light independent stage (equation)

Answer 6

• hydrogen used to reduce 6 molecules of carbon dioxide

- 1 molecule of glucose formed

Question 7

Overall equation

Answer 7

6 CO2 + 6H2O –> C6H12O6 + 6O2 (light energy & chlorophyll needed)

Question 8

Conditions essential for photosynthesis

Answer 8

• sunlight
• carbon dioxide
• chlorophyll
• suitable temp (enzyme rxns)
• water

Question 9

Limiting factors of photosynthesis

Answer 9

• light intensity
• conc of CO2
• temp

Question 10

What happens to glucose formed during photosynthesis

Answer 10

1. Used immediately
2. Stored as starch
3. Converted to sucrose
4. Form proteins
5. Fats

Question 11

Glucose used immediately in leaves

Answer 11

• cellular respiration
• provide energy for cellular activities
• form cellulose cell walls

Question 12

Stored as starch in leaves

Answer 12

• 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

Question 13

Converted to sucrose

Answer 13

• 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

Question 14

Glucose forms proteins

Answer 14

• 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

Question 15

Glucose converted to fats

Answer 15

• for storage
• cellular respiration
• synthesis of new protoplasm

Question 16

Importance of photosynthesis

Answer 16

1. Makes chemical energy available to animals and organisms
2. Removes CO2, provides O2
3. Energy is stored in fossil fuels thru photosynthesis

Question 17

Photosynthesis makes chemical energy available to animals and other organisms

Answer 17

• 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

Question 18

Photosynthesis removes CO2 and provides O2

Answer 18

• oxygen released used by living organisms respiration
• release energy for cellular activities
• purifies air
• maintains constant lvl of O2 an CO2 in air

Question 19

Energy is stored in fossil fuels through photosynthesis

Answer 19

• 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