Biology 1A    Sept 10, 1998
Lecture 5 - Photosynthesis

Page Contents :

• Reading Assignment
• Overview of Lecture
• Overview of Lab
• Lecture Outline
• Vocabulary
• Study Questions
• Related Websites

Stern: Chapter 10

Overview of Lecture:

Bacteria (cont'd)
Photosynthesis evolved in the cyanobacteria.
Eukaryotic photosynthesis is the result of endosymbiosis.
Overview of the Photosynthesis:
   The Overall Reaction
   Chloroplast Structure
   Pigments and Light
   The Photosystems
   Carbon Fixation
   Variation in Photosynthesis

Overview of Lab:

(A bullet indicates a handout.)
• Photosynthesis.

G. The Nitrogen Cycle
1. Atmosphere is 80% N2, a form inaccessible to life except for certain bacteria
2. nitrogen fixation
a. Converts N2 --> proteins using nitrogenase
b. This is inhibitted by oxygen, so it is compartmentalized (heterocysts)
c. Root nodules and symbiosis with plants (organic nitrogen for organic carbon)
3. decomposition : protein --> ammonia
4. chemosynthesis : ammonia --> nitrates, nitrites
5. denitrification : organic N --> N2
H. Cyanobacteria
1. Group of photosynthetic bacteria; contain chlorophyll
2. Often colonial
a. filamentous - cells connected in chains, usually sharing adjacent cell walls.
b. palmelloid - cells separate, but enclosed in a common mucilage sheath.

A. Single origin of life
1. 4.6 bya - earth formed
2. 3.8 bya - oldest rocks, Greenland
a. Presence of sedimentary rocks implies liquid water present
b. Atmosphere was reducing (CH4, CO2, N2, NH3)
c. Earth was hot and unfavorable to modern life
3. 3.6 bya - oldest fossil evidence of life in the form of rod-shaped microbes and stromatolites
4. Cyanobacteria - origins of photosynthesis
5. By 2 bya - huge micrbial diversity known
a. Origins of oxidizing (O2) atmosphere
b. Global catastrophy

A. Endosymbiosis - origin of mitochondria and plastids
B. The evidence for symbiosis
1. Double membranes
2. Contain own prokaryote-like ribosomes
3. Contain prokaryote-like DNA
4. DNA sequences are much like certain bacteria

A. The Overall Reaction
B. Chloroplast Structure
C. Pigments and Light
D. The Photosystems
E. Carbon Fixation
F. Variation in Photosynthesis

• Why is nitrogen important for life?

• UCMP - Photosynthesis
• UCMP - Introduction to the Cyanobacteria
• UCMP Glossary : Photosynthetic Pigments