Chapter 8b, Photosynthesis Flashcards
Light independent reactions also called
calvin benson cycle
Also called…
C3 Photosynthesis
The first detectable compound is…
3PG, a 3 Carbon compound
Step 1
CO2 added to RuBP to yield 2 molecules of 3PG
RuBP stands for
Ribulose Biphosphate
3PG stands for
3-phosphoglycerate
The enzyme involved in step one is…
ribulose biphosphate carboxylase-oxygenase
Step 2…
phosphorylation of reduction of 3PG to G3P using ATP and NADPH
G3P stands for
Glyceraldehyde 3-phosphate
Step 2 gets its ATP and NADPH from
non-cyclic photophosphorylation
Step 3…
Regeneration of RuBP via pentose phosphate pathways from G3P to continue the cycle
For every 6 CO2 that enter the cycle, _________________ are produced
6 net carbons of carbohydrate, OR 1 glucose
Light independent can also…
synthesize other organic molecules from the carbohydrates produced in photosynthesis
If carbons leave the cycle and synthesize something else, it…
reduces output of reaction
Photorespiration is when…
ribulose bisphosphate carboxylase-oxygenase add oxygen to RuBP instead of CO2 (if there is none availible)
Photorespiration produces…
1 molecule of 3PG and 1 molecule of glycolate which is respired but produces NO ATP
Respired means
broken down using oxygen
Photorespiration reduces..
overall pool of cellular carbohydrates when plant should be storing sugars
Photorespiration essentially…
undoes the calvin-benson cycle
Conditions for photorespiration…
- hot, dry, still
- plants have to close stomata to prevent water loss
- leads of low CO2 conditions as well
C4 photosynthesis..
- is a solution for photorespiration
- is a special type of light-independent reaction (light dependent still occurs)
Step 1 of C4 reactions…
CO2 is added to PEP by PEP carboxylase making oxaloacetate/malate (4 carbon compounds)
Step 2 of C4 reactions…
Oxaloacetate/malate break down TO pyruvate and CO2 which is then used in C3 photosynthesis (calvin cycle)
Step 3 of C4 reactions…
Pyruvate is phosphorylated (with ATP) to PEP to continue the cycle
Carbon dioxide capture (C4) occurs in
mesophyll cells
Oxaloacetate/malate is transferred to ______ _____ _____ where it generates CO2 for C3 photosynthesis
bundle sheath cells
Calvin cycle occurs in
bundle sheath cells
Light dependent occurs in
mesophyll
Effect of C4
CO2 pumped into bundle sheath cells, increasing local concentration, occurring in low O2 location
C3 plant anatomy
- MESOPHYLL CELLS: have C3 pathway, so can only do regular light independent reaction and light dependent reaction
- BUNDLE SHEATH CELLS: no photosynthesis occurs here, not completely surrounded by mesophyll cells
C4 plant anatomy
- MESOPHYLL CELLS: have C4/CO2 pump and light-dependent reactions, NO C3 PATHWAY
- BUNDLE SHEATH CELLS: have C3 pathways, completed SURROUNDED by mesophyll cells
CAM stands for
Crassulacean Acid Metabolism
CAM is a type of
light independent
CAM is found in
desert plants, even hotter and dryer environment
Difference from C4 is that…
- During NIGHT, CO2 fixed and stored as Oxaloacetate/malate until next day
- During DAY, CO2 released for C3 photosynthesis (calvin benson cylce) in same cell
CAM occurs on in the _____ cell
JUST IN mesophyll
Advantage of CAM is…
at night stomata can be open to capture CO2 without losing a lot of water vapor, during day stomata are closed to prevent water loss
Why do plants perform cellular respiration
plants produce and store carbohydrates to be able to break them down to ATP energy when needed, including at night and during winter
