Photosynthesis

Question 1

In the light dependent reaction what are the 2 forms of photophosphorylation

Answer 1

• cyclic- electron from PS I recycled to PS II

- non cyclic- NADPH as final acceptor and water as donor

Question 2

Explain the light dependent reaction

Answer 2

• photosystem 2 absorbs photon of light
• this excites the electrons to higher energy levels
• electron passed down electron transport chain to photosystem 1 and the electron is re-excited at photosystem 1
• as the electron is passed down the chain, it drops down energy levels in which the energy is used to pump H+ from the stroma into the thylakoid lumen
• NADP gets reduced (NADPH) and is the final electron acceptor
• the original e- is replaced through the oxidation of water
• the H+ in the thylakoid lumen diffuse back into the stroma through ATP synthase to produce ATP

Question 3

What is the equation for photosynthesis

Answer 3

Carbon dioxide + water –> Glucose + Oxygen

on arrow- sunlight, chlorophyll

Question 4

Explain the light independent reaction (Calvin Cycle)

Answer 4

• Ribulose bisphosphate reacts with Carbon dioxide and is catalysed by Ru Bis Co to form 2 molecules of Glycerate 3 phosphate
• ATP and NADPH react to form triose phosphate
• some Glycerate 3 phosphate recycled to RuBP using ATP
• some Glycerate 3 phosphate can be converted to useful organic substances

Question 5

What wavelength of light does photosystem II absorb

Answer 5

680nm

Question 6

What is an autotroph

Answer 6

an autotroph is an organism that uses an energy source to make complex carbohydrate

Question 7

Where does photosynthesis take place

Answer 7

chloroplast

Question 8

What reaction joins CO2 to Ribulose biphosphate

Answer 8

carbon fixation

Question 9

Where does the light independent reaction take place

Answer 9

stroma

Question 10

What are the two main groups of autotrophs

Answer 10

• Chemoautotrophs (bacteria) make carbohydrates using chemical energy
• Photoautotrophs-(plants + algae) use light energy to make carbohydrates

Question 11

Where in the chloroplast does the light dependent reaction happen

Answer 11

thylakoid membrane

Question 12

What products are taken from the light dependent reaction to the light independent reaction

Answer 12

• NADPH

- ATP

Question 13

What is another name for the light independent reaction

Answer 13

Calvin cycle

Question 14

What wavelength of light does photosystem I absorb

Answer 14

700nm

Question 15

What are the two stages of photosynthesis

Answer 15

• Light dependent stage

- Light independent stage

Question 16

What is an electron transport chain

Answer 16

a series of complexes that transfer electrons between electron donors and electron acceptors through redox reactions

Question 17

What is photoionisation

Answer 17

• photons of light excite the electrons in chlorophyl
• continued excitation causes the release of the electrons
• the e- can then be passed down electron transport chain

Question 18

What are the photosynthetic pigments found in chloroplasts

Answer 18

• chlorophylls e.g chlorophyll a and chlorophyll b

- carotenoids e.g carotene and xanthophyll