University:
Boston University
Course:
CAS CH 524 | Chemical Biology Laboratory
Academic year:

2022
Views:

229

Pages:

4
Author:

daven8b2x

ANABOLISM I Carbohydrates Photosynthesis and Carbohydrate Synthesis in Plants Introduction to Anabolic Pathways So far, we were mainly concerned with CATABOLISM: how to extract energy from biomolecules. The rest of the semester we’ll be concerned with ANABOLISM: how to build biomolecules. ANN Photosynthesis Metabolism • Carbon/oxygen cycle + CO2 + H2O ⇌ CH2O + O2 • Recall that living organisms are built of complex structures. • Building complex structures means paying a huge entropic price; need a constant input of energy. • The ultimate source of this energy on Earth is sunlight O2 + CH2O ⇌ H2O + CO2 Respiration Photosynthesis Key topics: • Photosynthetic electron transfer and photophosphorylation • CO2 assimilation in photosynthetic organisms • Photorespiration in C3 plants • Avoiding photorespiration in C4 plants Kornberg Lecture 03.17.17 (33:00-36:17) 3 min Key experiments: v Light caused O2 (Hill reaction) 4Fe+3(CN)6 ⇌ 4Fe+2(CN)6 v Light caused reduction of NADPH (Ochoa reaction) ∴light causes electron flow to NADPH (=A) ∴light causes electron flow, and O2 evolution that did not involve any CO2. ….The lack of involvement of CO2 in this light-caused oxygen production was definitively shown in 1941 Photosynthesis CO2 + H2O ⇌ CH2O + O2 Use heavy isotope of oxygen (18O) to ”label” the oxygen separately in CO2 and H2O, then test the O2 that is produced. Photosynthesis CO2 + H2O ⇌ CH2O + O2 Use heavy isotope of oxygen ( O) to ”label” the oxygen separately in CO2 and H2O, then test the O2 that is produced. 18 Photosynthesis CO2 + H2O ⇌ CH2O + O2 Light Energy is Converted to ATP in Plant Chloroplasts Photophosphorylation 2H2O ⇌ O2 + 4e– + 4H+ (2NADPH + 2H+) 4e– + 4H+ + CO2 ⇌ CH2O + H2O