Lecture 8

Question 1

Second stage

Answer 1

3CO2 + 9 ATP + 6H+ + 6NADPH = C3H6O3 phosophate + 9ADP + 8Pi + 6NADP+ + 3H2O

Question 2

Calvin cycle

Answer 2

Rubisco enzyme catalyses first step of cycle. Occurs in the chloroplast stroma and binds CO2 to organic substrate, reducing it. Occurs in stroma. 90% of plants.

Question 3

C4 photosynthesis

Answer 3

in all photosynthetic organisms, only Rubisco catalyses the net fixation of CO2 into organic molecules. Series of metbolic and structursl sdjustments exploiting phosphoenolpyruvate carboxylase to conc. CO2 around Rubisco. In mesophyll cell, CO2 diffuses in and dissolved to bicarbonate. Bicarbonate then fixes to Malate (C4) by enzyme PEPcase. Malate goes to bundle sheath cell and is decarboxylated, splitting off a C to fork CO2. plants in hot/sunny habitat. C4 in mesophyll and C3 in bundle sheath cells.

Question 4

Photorespiration

Answer 4

Convertes toxic 2-phosphoglycolate to 3-phosphoglycolate which can be used in the calvin cycle

Question 5

CAM metabolism

Answer 5

Solves Photorespiration and saves water. H2O is important for humidifying the leaf so it loses H2O but gains CO2 when stomata opens. if it opens at night, less H2O is lost. So, it opens at night. The CO2 diffuses in and converts to bicarbonate. PEP carboxylase fixes it into malate which sits in the vacuole. During the day, stomata closes and stored malate is decarboxylated around Rubisco. 7% plants hot/dry habitat. C4 night and calvin cycle day.