Lecture 3 - photosynthesis

Question 1

what is The importance of photosynthetic yield?

Answer 1

Free energy stored /year:
> 107 (ten million) kcal
C assimilated into organic matter /year:
> 1010 (ten billion) tons (without oceans)

10 % (tropics) – 20% (temperate) of land used by agriculture

Total grain yield /year:
2 x 109 (two billion) tons
109 (one billion) tons of C

World population increase: 6 9 billion in 2050
Needs grain production increase: 2  3.5 billion tons /year.
Required ∼100–200 million ha of new cropland

Question 2

what are chloroplasts?

Answer 2

complex and dynamic organelles

Question 3

what are the 2 major steps of photosynthesis?

Answer 3

Photosynthesis uses light energy to transform CO2 into organic carbon molecules.
Two major steps:
1. Energy capture (production of ATP, NADPH)
2. Build up of organic carbon molecules from CO2 (consumption of ATP and NADPH

Question 4

what is the general organisation of a photosystem?

Answer 4

Antenna complex: collects energy and tunnels it to the reaction centre
Reaction centre: produces high energy electron and passes it to quinone

Question 5

what is energy decay after light excitation?

Answer 5

In photosystems, chlorophyl molecules undergo process in the antenna complex, and process in the reaction centre

Question 6

what are the similarities and differences between chloroplast and mitochondria?

Answer 6

Differences: size and sub-compartmental structures
Similarities: mechanisms and their orientation with respect to stroma/matrix;
electron transport chain, chemiosmosis

Question 7

what are the types of photosynthetic reaction centres? and the differences between them?

Answer 7

Main differences:
Structure (PSII/Bact - PSI)
Donor of low-energy electrons (cytochrome –water – plastocyanin)

P900, P680 and P700