Life on Earth - Photosynthesis

Question 1

Describe Photosynthesis

Answer 1

• The process by which green plants and other organisms use sunlight to synthesize nutrients from carbon dioxide and water.
• Takes place inside the chloroplasts.
• Two stage process

Question 2

Name and describe the 1st stage of Photosynthesis

Answer 2

1. LIGHT REACTIONS
* Light energy from the sun is trapped by the chlorophyll in chloroplasts
* Light energy is converted into chemical energy used to make ATP.
* Water splits to produce hydrogen and oxygen
* Oxygen diffuses out of cell.
* Hydrogen and ATP → passed to Carbon Fixation

(ALL IN CHRONOLOGICAL ORDER)

Question 3

Name and describe the 2nd stage of Photosynthesis

Answer 3

2. CARBON FIXATION
* Series of enzyme-controlled reactions
* The ATP is broken down to release energy which is used to combine hydrogen (from light reactions) with carbon dioxide to produce sugar.
Hydrogen + Carbon dioxide → sugar

(ALL IN CHRONOLOGICAL ORDER)

Question 4

Photosynthesis word equation?

Answer 4

carbon dioxide + water → sugar + oxygen

(assisted by Light energy and Chlorophyll)

Question 5

List 4 fates (uses) of sugar

Answer 5

1. Energy source - used in respiration
2. Plant energy storage - can be made into glucose, then into starch
3. Plant building material - can be made into glucose, then into cellulose
4. Production of other types of food - sugar is a carb

Plants can combine sugar with nitrates to produce amino acids for proteins

Question 6

Define the term ‘Limiting factor’, applying it to photosynthesis and list the 3 limiting factors of photosynthesis

Answer 6

• Anything in short supply that prevents photosynthesis occurring at its maximum rate.
• Light intensity, Temperature, Carbon dioxide

Question 7

Describe the impact carbon dioxide concentration has on photosynthesis

Answer 7

• Required to make sugar during carbon fixation.
• No CO2? → No sugar

Question 8

Describe the impact light intensity has on photosynthesis

Answer 8

• Required to provide light for the light reactions.
• No light/low light intensity? → No ATP or Hydrogen for Carbon Fixation

Question 9

Describe the impact temperature has on photosynthesis

Answer 9

• Affects the rate the enzymes catalysing the reactions in both stages can occur.
• Temperature not at enzyme optimum? → Rate of photosynthesis declines.

Question 10

How is the rate of photosynthesis and the rate of plant growth linked?

Answer 10

Provides the energy plants need to grow and develop