(S5)C11- Photosynthesis

Question 1

What is the site of photosynthesis

Answer 1

Chloroplast

Question 2

Which Products are needed for the light dependent reaction

Answer 2

NADP, ATP, Pi and water

Question 3

Describe what happens during photoionisation in the light dependent reaction

Answer 3

-Chlorophyll absorbs light
-Excites the electrons inside the Chlorophyll
-Leave Chlorophyll
-Chlorophyll becomes positive

Question 4

Why are there changes in CO2 levels at different heights in a forest

Answer 4

-decrease in carbon dioxide concentration with height
-at ground level there is: less light/more animals respiring/fewer leaves.

Question 5

Why are there changes in CO2 levels at different times of the day

Answer 5

-High concentration of CO2 at night and darkness
-no photosynthesis as light is required for the light dependent reaction
-at night time a lot of plants and other organisms respire (releasing CO2)

Question 6

Describe the process of the light-independent reaction.

Answer 6

1) CO2 + RuBP to form glycerate 3- phosphate (GP). Catalysed by rubisco

2) GP reduced to form 2x triose phosphate (TP) using energy from ATP and by accepting a Hydrogen from NADPH

3) One carbon leaves the TP each time it goes round the cycle. (builds up to a hexose sugar (Glucose))

4) The rest of the molecule is used to regenerate RuBP with energy from ATP

Question 7

Name 3 limiting factors

Answer 7

Temperature, carbon dioxide, light intensity

Question 8

What is the name for the process of the light independent reaction

Answer 8

calvin cycle

Question 9

Where does the light independent reaction take place

Answer 9

Stroma

Question 10

What is the enzyme used in the light independent reaction

Answer 10

Rubisco

Question 11

What are the 2 products that breaks down glycerate 3-phosphate

Answer 11

ATP and Reduced NADP (NADPH)

Question 12

What are the 4 stages of the light dependent reaction

Answer 12

photoionisation
photolysis
chemiosmosis
production of ATP and NADPH

Question 13

Explain the process of the light dependent reaction

Answer 13

1) Light energy absorbed by chlorophyll
2) Excites the electrons to leave chlorophyll (ionised)
3) The energy from the release of electrons is used to make ATP and NADPH

4) more light energy absorbed by chlorophyll which is used to breakdown water into oxygen,H+ and e-
5) the H+ is picked up by NADP to form NADPH, oxygen is used for respiration and the electron is passed along the electron transport chain

6) as the electrons move along the proteins in the electron transport chain they release energy
7) this energy is used to transport protons in the stroma across the membrane to the thylakoid lumen
8) high concentration on this side of the membrane (electrochemical gradient)
9) therefore protons pass through the ATP synthase which changes the shape of the protein which creates energy for ATP resynthesis

Question 14

heat decreases the light dependent reaction. explain why it leads to a decrease in the light independent reaction

Answer 14

• ATP isn’t produced
  -NADPH isn’t produced

Question 15

why does a decrease in the activity of the enzyme rubisco limit the rate of photosynthesis

Answer 15

less carbon dioxide reacting with RuBP
less Gp being produced