module 2 - 17.3 photosynthesis (2) Flashcards
what are the 2 stages of photosythesis?
- light dependent stage
- light independent stage
what is the light dependent stage of photosynthesis?
- light energy is transferred to high energy electrons
- ATP made from ADP + Pi
- water split into H+, e- and O2
- reduced NADP made from NAD and H
what is the light independent stage of photosynthesis?
- CO2 is fixed by adding hydrogen atoms to make triose phosphate (TP)
- reduced NADP supplies hydrogen
- ATP supplies energy
what is the process of the light dependent stage of photosynthesis?
SUMMARY:
- occurs in thylakoid membranes
- 2 types of photosystems are used: PSI AND PSII
- ATP is made by chemiosmosis and photophosphorylation
- water molecules are split into H+, e- and O2 by photolysis
- NADP converted to reduces NADP to create reducing power
what is the process of the light independent stage of photosynthesis?
SUMMARY:
- occurs in the stroma
- uses carbon dioxide from the air
- uses ATP and reduced NADP from light dependent stage
- produces first organic molecule (triose phosphate)
- also called calvin cycle
- is a series of biochemical reactions controlled by enzymes
where does every organic molecules in plants come from?
triose phosphate
what is photorespiration?
- RUBISCO has high affinity for CO2, also competitively inhibited by O2
- when oxygen binds to RUBISCO’s active site,phosphoglycolate is made instead of 6 carbon intermediate (reduces efficiency of calvin cycle)
- phosphoglycolate is a 2 carbon molecule toxic to plants
- plants get rid of phosphoglycolate by converting it to non-toxic waste chemicals (requires lots of ATP & reduced NAD from light dependent stage)
- this reduces amount of CO2 in chloroplasts but photolysis of water still produces O2 so even more O2 binds to RUBISCO
- plants have adapted to this by over producing RUBISCO in chloroplast
