Photosynthesis Chapter 10
• Photoautotrophs are • Chemoautotrophs are
Photosynthesis is a redox process Photosynthesis is a redox process Water is oxidized, carbon dioxide is Water is oxidized, carbon dioxide is reduced • Photosynthesis – Occurs in plants, algae, certain other protists, and some prokaryotes These organisms use light energy to drive the synthesis of organic molecules from carbon dioxide and (in most cases) water. They feed not only themselves, but the entire living world. (a) On land, plants are the predominant producers of food. In aquatic environments, photosynthetic organisms include (b) multicellular algae, such as this kelp; (c) some unicellular protists, such as Euglena; (d) the prokaryotes called cyanobacteria; and (e) other photosynthetic prokaryotes, such as these purple sulfur bacteria, which produce sulfur (spherical globules) (c, d, e: LMs). (a) Plants (b) Multicellular algae (c) Unicellular protist 10 μ m 40 μ m (d) Cyanobacteria 1.5 μ m (e) Pruple sulfur bacteria Figure 10.2
Chloroplasts: The Sites of Photosynthesis in Plants • The leaves of plants – Are the major sites of photosynthesis Vein Leaf cross section Figure 10.3 Mesophyll CO 2 O 2 Stomata
• Chloroplasts – Are the organelles in which photosynthesis occurs – Contain thylakoids and grana Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner membrane Thylakoid space Thylakoid Granum Stroma 1 µm
Chloroplast Inheritance • Note ! Plant cells often lack centrosomes (that are found in animals) • Microtubules form from the cell periphery • Chloroplasts are inherited only from 1 parent mostly • Chloroplast DNA replication is not associated with Genome DNA replication so chloroplasts replicate at different times in the cell cycle • Look ! New Cell Wall and membrane (cell plate) is made by the joining of vesicles. Does this remind you of something, G?
Tracking Atoms Through Photosynthesis: • Photosynthesis is summarized as 6 CO 2 + 12 H 2 O + Light energy → C 6 H 12 O 6 + 6 O 2 + 6 H 2 O
The Splitting of Water • Chloroplasts split water into – Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules 6 CO 2 12 H 2 O Reactants: Products: C 6 H 12 O 6 6 H 2 O 6 O 2 Figure 10.4 Where does this occur?
The Two Stages of Photosynthesis: A Preview • Photosynthesis consists of two processes – The light reactions = Occur in the grana, Split water, release oxygen, produce ATP, and form NADPH –
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