Lecture 12: Photosynthesis - 10/27

Question 1

What are the 3 stages of the Calvin/C3 cycle?

Answer 1

Carboxylation
Reduction
Regeneration

Question 2

What are the 3 important chemicals in the Calvin cycle?

Answer 2

3-PGA (3-phosphogylcerate)
G3P (glyceraldehyde-3-phosphate)
RuBP (Ribulose-1,5-biphosphate)

Question 3

How does the Calvin cycle work?

Answer 3

RuBP, CO2, and H2O are used to produce 3-PGA, which is then reduced to form G3P.

For every 3 RuBP molecules, one G3P molecule is produced. Multiple G3P molecules are then synthesized into sucrose.

The rest of the G3P molecules are recycled back into RuBP.

Question 4

Rubisco enzyme

Answer 4

Ribulose-1,5-biphosphate carboxylase/oxygenase

Catalyzes RuBP carboxylation (addition of CO2)

The most abundant protein on the planet. Make sure not to confuse this enzyme with RuBP, the substrate!

Question 5

What is the net output, G3P, of the Calvin cycle used for?

Answer 5

Building starch in chloroplasts
Making sucrose in the cytosol
Entering glycolysis in the cytosol to contribute to cellular respiration

Question 6

Transitory starch

Answer 6

Starch that is made during the day and stored in the stroma. It is degraded at night so the plant has energy

Question 7

Storage starch

Answer 7

Can be made at any time and are deposited in sink tissues. The synthesis of this kind of starch occurs in amyloplasts

Question 8

How does the intensity of light effect photosynthesis?

Answer 8

The more intense the light, the greater the rate of light reactions

Question 9

Shade leaves

Answer 9

Thinner leaves with greater area

Question 10

Sun leaves

Answer 10

Thicker and less wide

Question 11

Why is there carboxylase/oxygenase in Rubisco’s name?

Answer 11

Because it can act as both a carboxylase and oxygenase

If CO2 is used, the reaction in the Calvin cycle will produce two 3-phosphoglycerate (has 6 carbons)

If O2 is used, the reaction will produce 3PGA and 2-phosphoglycolate (5 carbons). This is because there wasn’t a C from CO2