Chapter 8.6: Carbon Fixation: The Calvin Cycle Flashcards

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1
Q
A
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2
Q

What happens during reduction?

A

o PGA is reduced by G3P

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3
Q

Define Calvin Cycle

A

the dark reactions of C3 photosynthesis

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4
Q

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?

A

C3 photosynthesis

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5
Q

Define C3 photosynthesis

A

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

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6
Q

How are carbohydrates built?

A

• 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

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7
Q

the four-subunit enzyme in the chloroplast that catalyzes the carbon fixation reaction joining CO2 to RuBP

A

• Ribulose Biphosphate Carboxylase/Oxygenase (rubisco)

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8
Q

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?

A

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

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9
Q

What is the net equation of the Calvin cycle?

A

• 6CO2 + 18 ATP + 12 NADPH + water  2 glyceraldehyde 3-phosphate + 16 Pi + 18 ADP + 12 NADP+

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10
Q

What is in the Calvin cycle, the 5-carbon sugar to which CO2 is attached, accomplishing carbon fixation?

A

 Ribulose 1,5-Biphosphate (RuBP)

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11
Q

What are the 3 phases of the Carbon cycle?

A
  1. Carbon Fixation 2. Reduction 3. Regeneration of RuBP
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12
Q

Define  Ribulose 1,5-Biphosphate (RuBP)

A

in the Calvin cycle, the 5-carbon sugar to which CO2 is attached, accomplishing carbon fixation

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13
Q

What is the first step of the Calvin cycle?

A

o Photosynthetic cells produce ribulose 1,5-biphosphate (RuBP) by reassembling the bonds of fructose 6-phosphate and glyceraldehyde 3-phosphate (G3P)

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14
Q

What is the dark reactions of C3 photosynthesis?

A

calvin cycle

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15
Q

What happens during carbon fixation?

A

o Generates two molecules of the 3-carbon acid PGA

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16
Q

After 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 next step of the Calvin cycle?

A

o CO2 reacts with RuBP to form a 6-carbon intermediate that immediately splits into two molecules of the 3-carbon 3-phosphoglycerate (PGA)  Called carbon fixation reaction because inorganic carbon (CO2) has been incorporated into an organic form: the acid PGA  Carried out by the enzyme rubisco

17
Q

What happens during regenration of RuBP?

A

o PGA is used to regenerate RuBP

18
Q

Define • Ribulose Biphosphate Carboxylase/Oxygenase (rubisco)

A

the four-subunit enzyme in the chloroplast that catalyzes the carbon fixation reaction joining CO2 to RuBP