3.3 The Light-independant Reaction

Question 1

What are the products of the LDR used to do

Answer 1

(ATP and reduced NADP) Are used to reduce carbon dioxide in the second stage of photosynthesis

Question 2

Unlike the the first stage, what does this stage not require

Answer 2

Light directly, and occurs wether or not light is available

Question 3

What does the light-independent reaction require

Answer 3

The products of the LDR stage and so rapidly ceases when light is absent

Question 4

Where does the light-independent reaction take place

Answer 4

In the Stroma of the chloroplasts

Question 5

What is the Calvin cycle

Answer 5

A biochemical pathway that forms part of the LIR of photosynthesis, during which carbon dioxide is reduced to form carbohydrate

Question 6

Draw the Calvin cycle

Answer 6

Page 38

Question 7

What are the 3 stages of the Calvin cycle

Answer 7

1) fixation stage
2) reduction stage
3) regeneration of RuBP

Question 8

What is the fixation stage of the Calvin cycle

Answer 8

Co2 joined to RuBP to make 2 x 3cGP

Question 9

What Is the reduction stage of the Calvin cycle

Answer 9

• GP is reduced to TP using RNADP(reduced NADP)
• RNADP is oxidised, GP is reduced - a redox reaction
• energy from the hydrolysis of ATP is also used

Question 10

What is the regeneration stage of the Calvin cycle

Answer 10

• some of the TP is converted to 6 carbon sugar

- the rest is used to regenerate molecules of RuBP to complete the cycle

Question 11

Where does the LIR take place

Answer 11

In the Stroma of the chloroplasts

Question 12

How are chloroplasts adapted to carrying out the LIR of photosynthesis

Answer 12

• fluid of the Stroma contain all the enzymes needed to carry out the LIR
• the Stroma fluid surrounds the grana and so the products of the LDR in the grana can readily diffuse into the Stroma
• contains both DNA and ribosomes so it can quickly and easily manufacture some of the proteins needed for the LIR

Question 13

Calving lollipop experiment method

Answer 13

1) algae are grown under light in the transparent lollipop
2) radioactive 14C in the form of hydrogencarbonate is injected
3) at intervals samples of the photosynthesising algae are dropped into the hot methanol to stop chemical reactions
4) the 2 compounds in the algae are separated by two-way chromatography
5) radioactive compounds are identified and the pathway is determined by the time at which each first appear. The first to appear is the first pathway

Question 14

What are the products of the light-dependant reaction of photosynthesis

Answer 14

ATP and reduced NADP