Photosynthesis

Question 1

What are the 2 processes of photosynthesis?

Answer 1

1. Light-dependent
2. Light-independent (Calvin cycle)

Question 2

What is the equation for photosynthesis?

Answer 2

6CO2+6H2O→C6H12O6+6O2
light energy

Question 3

What is the importance of photosynthesis?

Answer 3

1. It provides carbon sources and energy to all living organism
2. It produces O2 which is vital for all aerobic forms of life.
3. It produces the energy-containing fuels e.g oil?

Question 4

Where does photosynthesis take place generally?

Answer 4

Chloroplast

*specifically due to presence of chlorophyll which is found in chloroplast.

Question 5

How does feature of thylakoid membrane help the chloroplast?

(2 features)
(4 advantages)

Answer 5

They present a larger surface area for
1. ↑ distribution of photosynthetic pigments to harvest LE
2. ↑ enzymes (ATP synthase) for synthesis of ATP
3. ↑ e- carriers for the transport of e- along the ETC

They are impermeable to H+ :
4. allows for formation of proton pool in the thylakoid lumen for synthesis of ATP via chemiosmosis

Question 6

What are photosynthetic pigments?

Answer 6

1. Chlorophylls :
   - green pigments that absorb mainly red and blue-violet light, reflecting green light
   - chlorophyll a is found at the reaction centre of a photosystem
2. Carotenoids :
   - yellow, orange pigments that absorb light in blue-violet range
   - act as accessory pigments

Question 7

Explain the absorption spectrum of photosynthetic pigments.

Answer 7

A graph showing the relative absorbance of different wavelengths of light of a pigment.

Question 8

Explain the action spectrum of photosynthetic pigments.

Answer 8

A graph showing the effectiveness of different wavelengths of light in stimulating the process.

Question 9

What is the advantage of accessory pigments not absorbing the same wavelengths of chlorophyll a?

Answer 9

Accessory pigments enable the plants to utilise the other wavelengths of light that could not be trapped by chlorophyll a alone

Question 10

What are photosystems and where are they found?

Answer 10

Light absorbing pigment organised into units and found in the thylakoid membranes

Question 11

What does the photosystem consists of?

Answer 11

A protein complex made up of a reaction centre complex (contains chlorophyll a) and many light harvesting complexes (contains accessory pigments)

• a group of chlorophyll molecules held tgt by protein

Question 12

Where are the 2 forms of chlorophyll a found in and why?

Answer 12

Photosystem I with reaction centre P700
- most reactive and best in absorbing light at wavelength of 700nm

Photosystem II with reaction centre P680
- most reactive and best in absorbing light at wavelength of 680nm

Question 13

What are photons and what is its use?

Answer 13

photons = light energy in discrete packets
- they are abosorbed by chlorophyll molecule in a photosystem

Question 14

What are the structures for chemiosomis in chloroplast?

Answer 14

1. where protons accumulate - THYLAKOID LUMEN/SPACE
2. where ATP synthase is embedded in - THYLAKOID MEMBRANE
3. where high energy electrons come from - STROMA

Question 15

What is photophosphorylation?

Answer 15

Conversion of light energy into chemical energy in the form of ATP.

Question 16

What are the 2 types of photophosphorylation?

Answer 16

1. Non-cyclic photophosphorylation (linear)
2. Cyclic phosphorylation