Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 432

Biochemistry

Spring 2009

Lecture Notes: 23 January

© R. Paselk 2006
 
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Photosynthesis

Look at chloroplast structure [overhead]. Note how the thylakoids are stacked, with granal lamellae between stacked thylakoids, and stromal lamellae facing the plastisol (chloroplast matrix). The components of the photosynthetic ETS will be differentially distributed between these two lamellae. Most of protons will be pumped into the lumen of the thylacoid system. (The important thing here is that the protons are being pumped out of the plastisol.)

The Light Reactions

Let's look a bit at chlorophyll (text Figure 19-40, p 726) and its interaction with light.[overheads] Find that there are many chlorophylls/active center. That is, only a small portion of the chlorophyll pool is actually involved in using the light energy (1/300 in Chlorella). What do the rest do? Act together as an antenna (text Figure 19-45, p 729) [overhead, L]. The transfers between molecules take <10-10 sec with an efficiency of >90%. Higher plants also have beta-carotenes (text Figure 19-40, p 726) to absorb other light frequencies. Aquatic plants have different dyes, since only blue-green light penetrates to depth.


Pathway Diagrams

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Last modified 27 January 2009