Photosynthesis Light-Dependent Reactions

Question 1

Light excites electrons in chlorophyll imbedded in thylakoid membrane

Answer 1

energized electrons can be transferred to a primary electron acceptor (redox reaction)

Question 2

2 stages of light reactions

Answer 2

1. Capturing light energy
2. Using captured light energy to synthesize ATP

Question 3

When do light reactions start?

Answer 3

when light energy is absorbed

Question 4

Photons strike photosynthesis and broken into 3 steps

Answer 4

1. Photooxidation
2. Electron Transport
3. Chemiosmosis

Question 5

Photooxidation

Answer 5

absorption of a photon by an electron of chlorophyll by primary electron acceptor (PEA)

Question 6

Electron Transport

Answer 6

transfer of excited electron through series of membrane bound electron carriers
- pumping of proton through the thylakoid membrane

Question 7

Chemiosmosis

Answer 7

movement of protons through ATP synthase to drive the photophosphorylation of ADP to ATP

Question 8

What is a photosystem?

Answer 8

protein complex composed of pigments

Question 9

What is the reaction centre made of?

Answer 9

chlorophyll a and specific proteins

Question 10

Chlorophyll a

Answer 10

loses electrons

Question 11

Cyclic photophosphorylation

Answer 11

• only involves (PS1)
• produces ATP
• ## electrons repeatedly flow through PS1 and the first part of ETC

Question 12

Non-Cyclic photophosphorylation

Answer 12

• both PS1 and PS2
• produces ATP and NADPH
• electrons flow in a line from water the NADPH

Question 13

What are the Photosystems?

Answer 13

PS1 (P700) PS2 (680)

Question 14

Steps 1-3

Answer 14

1. Photons absorbed by antenna pigments causing them to move from ground state to excited
2. Excited energy is passed along chlorophyll until it reaches reaction centre
3. Chlorophyll a in reaction centre absorbs the energy

Question 15

Steps 4-5

Answer 15

4. The high-energy state of chlorophyll a causes it to emit 2e
5. The primary electron acceptor takes electrons from chlorophyll a (photoexcitation or photooxidation)

Question 16

End results

Answer 16

NADPH and ATP- used to synthesize glucose

Question 17

Photolysis

Answer 17

PS2 acquires a supply of electrons by using the sun’s energy to hydrolyze water (non-cyclic electron pathway)