Photosynthesis (Johnson)

Question 1

How many power does the sun deliver per year?

Answer 1

100 000 TW

Question 2

How much power do humans use annually?

Answer 2

15 TW

Question 3

The energy in all of Earth’s oil resources is provided by the sun in how long?

Answer 3

1.5days

Question 4

How much power does chlorophyll capture annually?

Answer 4

~100TV

Question 5

What are humankind’s biggest problems?

Answer 5

Food/Energy/Less CO2

Question 6

Name the four types of photosynthetic organism

Answer 6

Eukaryotic oxygenic photosynthesis Prokaryotic oxygenic photosynthesis Archael photosynthesis Prokaryotic anoyxgenic photosynthesis

Question 7

Name some photosynthetic organisms found in each type

Answer 7

EOP

Plants, Mosses, Green/Red/Brown Algae

POP

Cyanobacteria (-)

AP

Halobacteria

PAP

Purple Bacteria (-), Purple Sulphur Bacteria (-), Green Sulphur Bacteria (-), Green Gilding Bacteria (-), Heliobacteria (+)

Question 8

Where does photosynthetic electron transfer take place?

Answer 8

The thylakoid membrane

Question 9

Where does CO2 fixation take place?

Answer 9

In the stroma.

Question 10

What is plastoquinone and where is it found?

Answer 10

A lipid soluble electron carrier in the PET chain.

Question 11

What is cytochrome b₆-f complex equivalent to?

Answer 11

The respiration Q cycle

Question 12

How many light-driven reactions occur, and where?

Answer 12

2 at both Photosystem I and II

Question 13

What do antenna complexes do?

Answer 13

Absorb photos and pass ‘excitation energy’ to the reaction centre.

Question 14

What is special about the reaction centre chlorophylls?

Answer 14

They are redox active

Question 15

What are the main structuraly components of the chlorophyll molecule?

Answer 15

• A tetrapyrolle ring that coordinates a Mg²⁺ ion
• A hydrophobic pytyl tail
• A conjugated pi electron sstem at the ring that is responsible for photon absorption

Question 16

What wavelength photon promotes an S₀ electron to S₁?

Answer 16

656nm

Question 17

S₀ and S₁ are electronic states of the molecule. Chlorophyll is a complex molecule (large pi electron system): what does this mean, with regards to its electronic states?

Answer 17

There are multiple vibrational sub-levels for each electronic state.

Question 18

How long does light absorption take?

Answer 18

1fs

Question 19

Why can chlorophyll light absorption be plotted as a gaussian distribution?

Answer 19

Not every transition has the same probability of being populated as others.

Question 20

What is the name for the process where a promoted electron and falls to a lower sub-level?

Answer 20

Vibrational relaxation

Question 21

What is the name for the process where an electron falls to the next lowest electronic state?

Answer 21

Internal conversion

Question 22

Vibrational relaxation and internal conversion in S2-S1 occur on what timescale?

Answer 22

Ultrafast (picosecond)

Question 23

Why does internal conversion from S1 –> S2 occur on the nanosecond timescale?

Answer 23

The electron is closer to the nucleus - the excited state is more stable.

Question 24

What de-excitation channel can compete with S1–>S0 internal conversion?

Answer 24

Fluorescence?

Question 25

From which vibrational sub-level does fluorescence only occur?

Answer 25

The lower sub-level.