#5: Light Dependant Reactions

Question 1

Photosynthesis

Answer 1

process used by plants to produce glucose

3 stages:

1. Capturing light energy
2. Using captured light energy to make ATP and NADPH
3. Using ATP and NADPH to make glucose from CO2

Question 2

Photosynthesis Equation

Answer 2

6 CO2 + 6 H20 = glucose + 6 O2

Question 3

Chloroplasts

Answer 3

site of photosynthesis in plant cells

consists of:

1. An inner and outer membrane
2. Thylakoids
3. Grana (stacks of thylakoids)
4. Stroma (a liquid-like substance)

Question 4

Pigment

Answer 4

a pigment is a compound that absorbs part of the spectra of visible light and reflects the rest

chlorophyll is a pigment

Question 5

Chlorophyll a

Answer 5

absorbs light in the blue-violet and red spectra of visible light

chlorophyll a is the only pigment that can transfer light energy to the reactions of photosynthesis

Question 6

Accessory pigments

Answer 6

accessory pigments must give the light-energy they have collected to chlorophyll a in order for the energy to be used in photosynthesis

Examples:
Chlorophyll b
absorbs light in the blue-violet and red spectra of visible light

Carotenoids
absorbs light in the blue-violet spectra of visible light

Question 7

Capturing Light

Answer 7

Light must hit a cluster of proteins and pigments in the thylakoid membrane to begin process
Photon of light excites a single electron moving it to a higher energy state.
(3 Options)
Carotenoids/chlorophyll b transfer their energy to chlorophyll a (referred to as an antenna complex)
Energy hits chlorophyll a (reaction centre) and an electron is released to the electron transport chain

Question 8

3 outcomes for an excited electron

Answer 8

1. Releases energy as thermal energy
2. Transfers energy to a different electron in neighbouring pigment molecule
3. Electron is accepted by an electron-accepting molecule

Question 9

Stage 1 - Photoexcitation

Answer 9

absorption of light energy by photosystems
photosystems are clusters consisting of chlorophyll a, accessory pigments, and pr- in the membrane of thylakoids

• energy from photons of light are transferred through the photosystem until it reaches chlorophyll a
• chlorophyll a uses the energy to excite an e-
• the excited e - will then be passed on through the reactions of photosynthesis (redox reactions)

Question 10

Two primary components of photosystems

Answer 10

1. Antenna Complex
   - contains accessory pigments
   - responsible for collecting light energy
2. Reaction Centre
   - contains chlorophyll a
   - responsible for transmitting light energy into the reactions of photosynthesis

Question 11

Two types of photosystems used in photosynthesis

Answer 11

1. Photosystem I - contains chlorophyll a P700

2. Photosystem II - contains chlorophyll a P680

Question 12

Stage 2 – e- Transport

Answer 12

excited e - from chlorophyll a are transferred through series of compounds that reduces NADP+ to NADPH and pumps H+ into the thylakoid space

Question 13

Stage 3 – Chemiosmosis

Answer 13

H + gradient produced during e - transport is used to make ATP via ATP synthase