Chapter 8.6: Carbon Fixation: The Calvin Cycle Flashcards
What happens during reduction?
o PGA is reduced by G3P
Define Calvin Cycle
the dark reactions of C3 photosynthesis
What is the main cycle of the dark reaction, in which CO2 binds to ribulose 1,5-biphosphate (RuBP) to form two 3-carbon phosphoglycerate (PGA) molecules?
C3 photosynthesis
Define C3 photosynthesis
the main cycle of the dark reaction, in which CO2 binds to ribulose 1,5-biphosphate (RuBP) to form two 3-carbon phosphoglycerate (PGA) molecules
How are carbohydrates built?
• To build carbohydrates, cells use energy and a source of electrons produced by the light-dependent reactions of the thylakoids o Energy ATP (provided by cyclic and noncyclic photophosphorylation) drives the endergonic reactions o Reduction Potential NADPH (provided by photosystem I) provides a source of protons and the energetic electrons needed to bind them to carbon atoms
the four-subunit enzyme in the chloroplast that catalyzes the carbon fixation reaction joining CO2 to RuBP
• Ribulose Biphosphate Carboxylase/Oxygenase (rubisco)
After o CO2 reacts with RuBP to form a 6-carbon intermediate that immediately splits into two molecules of the 3-carbon 3-phosphoglycerate (PGA), what is the last step of the Calvin cycle?
o Carbon is Transferred Through Cycle Intermediates, Eventually Producing Glucose 6 molecules of CO2 are bound to six RuBP by rubisco to produce 12 molecules of PGA (containing 36 carbon atoms in all) The 36 carbon atoms then undergo a cycle of reactions that regenerates the six molecules of RuBP used in the initial step (containing 30 carbon atoms) • This leaves two molecules of glyceraldehyde 3-phosphate (G3P) (each with three carbon atoms) as the net gain These two molecules of G3P can then be used to make one molecule of glucose
What is the net equation of the Calvin cycle?
• 6CO2 + 18 ATP + 12 NADPH + water 2 glyceraldehyde 3-phosphate + 16 Pi + 18 ADP + 12 NADP+
What is in the Calvin cycle, the 5-carbon sugar to which CO2 is attached, accomplishing carbon fixation?
Ribulose 1,5-Biphosphate (RuBP)
What are the 3 phases of the Carbon cycle?
- Carbon Fixation 2. Reduction 3. Regeneration of RuBP
Define Ribulose 1,5-Biphosphate (RuBP)
in the Calvin cycle, the 5-carbon sugar to which CO2 is attached, accomplishing carbon fixation
What is the first step of the Calvin cycle?
o Photosynthetic cells produce ribulose 1,5-biphosphate (RuBP) by reassembling the bonds of fructose 6-phosphate and glyceraldehyde 3-phosphate (G3P)
What is the dark reactions of C3 photosynthesis?
calvin cycle
What happens during carbon fixation?
o Generates two molecules of the 3-carbon acid PGA