Question

1. Explain what is represented in the following image, and how it relates to BOTH the Calvin-Benson cycle photosynthesis (sometimes called the reductive pentose phosphate pathway) AND the oxidative pentose phosphate pathway in plastids (3 pts)

2. What happens during the three stages of the Calvin-Benson Cycle (3 points)

Carboxylation:

Reduction:

Regeneration:

3. It is July in Texas and day-time high temperatures have exceeded 100°F for 40 days straight without any rain.  The sun has not been blocked by any clouds and the raspberry plants in Dr. Ayre’s backyard are thriving from all the photosynthesis.  TRUE or FALSE.
EXPLAIN your answer (1 pt):

4. The first “product” of the Calvin Cycle that is not recycled to make more substrate is a phosphorylated 3-carbon sugar.  If that sugar stays in the chloroplast, it will most likely be converted to ________________; if it is transported to the cytoplasm it will most likely be converted to ________________; and the protein that controls the distribution of that 3-carbon sugar is ____________________________ (specific names required, 3 pts)

5. A popular quote incorrectly attributed to Mark Twain is "The coldest winter I ever spent was a summer in San Francisco".  Based solely on this quote, what type of photosynthetic chemistry would you expect to find among the majority of plants growing in the area?  Why, specifically, would your chosen chemistry be better than the other possibilities (2 pts)?

Answer 1

2. Calvin-Benson Cycle- This cycle takes place in the stroma of chloroplast. The light reaction products i.e. ATP and NADPH help in fixing carbon atom of CO2 in three carbon sugars.

This cycle has three stages-

1. Carboxylation or carbon fixation- By the help of the enzyme RuBP carboxylase/oxygenase, or RUBISCO, a CO2 molecule combines with ribulose-1,5-bisphosphate (RuBP) i.e. a five-carbon molecule giving rise to a six-carbon compound that further breaks into two molecules of a three-carbon compound 3-phosphoglyceric acid (3-PGA).

2. Reduction- In reduction, the light reaction products ATP and NADPH are used to convert the 3-PGA molecules into molecules of a three-carbon sugar, glyceraldehyde-3-phosphate (G3P). In this reaction, NADPH donates electrons to reduce a three-carbon intermediate to make G3P.

3. Regeneration- Few glyceraldehyde-3-phosphate will make glucose, while others must be recycled to regenerate the RuBP acceptor by the help of ATP.

The attached diagram is showing Calvin Benson cycle.

Thanking you

ate RuBISCO CARBON AXATION 3 ADP 6 ATP REGENERATION REDUCTION NADPH 6 NADP