09-05-2012, 10:27 AM
Artificial Photosynthesis
Artificial Photosynthesis (1).ppt (Size: 889 KB / Downloads: 123)
Purpose
A closed system that includes human metabolism
Existing systems
Apollo and Shuttle carried bottled oxygen and lithium-hydroxide
fine for a few days supplies too great to last months
Mir and ISS use electrolysis of water, recycled from dehumidifier and urine collection, CO2 removed with reusable sorbent
only half of oxygen breathed is recycled
other half of oxygen breathed is sequestered in CO2 and dumped
Carbohydrate model
Carbohydrates are relatively simple to model.
Starch, pectin, and dextrose are polysaccharides (C6H10O5)nC6H12O6
Human metabolism starts by hydrating to break into monosaccharide:
(C6H10O5)nC6H12O6 + n H2O → (n+1) C6H12O6
We can use formuli for monosaccharides to analyze all carbohydrates.
Cellular respiration of monosaccharides is:
6 O2 + C6H12O6 → 6 H2O + 6 CO2
Photosynthesis is the reverse of this:
6 H2O + 6 CO2 → 6 O2 + C6H12O6
Replicating photosynthesis
Photosynthesis in plants occurs in an chloroplasts.
This is a two step process:
Light reaction (Photophosporylation)
Capture light with chlorophyll
Convert ADP into ATP, and NADP+ into NADPH
Water is broken up, and oxygen released
Dark reaction (Calvin-Benson cycle)
ATP broken back into ADP, NADP+ into NADPH
Net reaction: CO2 and hydrogen make sugar
Light reaction details
Chlorophyl act as antennae to collect light
pheophytin cleaves 2 H2O into O2, 4 H+, 4 e-
cytochrome complex pumps 4 more H+ into thylakoid interior
NADP reductase converts NADP+, H+, and 2 e- into NADPH
ATP synthase converts ADP and Pi into ATP, releases H+ from thylakoid