Question

The cost of NOT performing 2 cycles of photorespiration is

1 C in the form of CO2

4 C in the form of 2 molecules of phosphoglycolate

1 C (as CO2), 2 ATP, 2 NADPH equivalents, and one molecule of NH4+

3 ATP and 2 NADPH

5 ATP and 2 NADPH

As temperature increases, the quantum yield of photosynthesis in C3 plants is directly affected by

The decreasing ratio of CO2 to O2 in the aqueous phase

The increasing ratio of CO2 to O2 in the aqueous phase

The decreasing ratio of CO2 to O2 in the gas phase

The increasing ratio of CO2 to O2 in the gas phase

In CAM plants and ‘regular’ C4 plants, the enzyme that first fixes CO2 into an organic molecule is

Ribulose 1,5-bisphosphate carboxylase/oxygenase for both

Phosphoenolpyruvate carboxylase (PEPC) for both

NADP-malic enzyme for both

Rubisco in CAM, PEPC in ‘regular’ C4

Rubisco in ‘regular’ C4, PEPC in CAM

In CAM (crassulacean acid metabolism) plants, when and where

are sugars produced?

During the night, in mesophyll cells

During the day, in mesophyll cells

During the night, in bundle sheath cells

During the day, in bundle sheath cells

QUESTION 10

In ‘regular’ C4 plants, when and where are sugars

produced?

During the night, in mesophyll cells

During the day, in mesophyll cells

During the night, in bundle sheath cells

During the day, in bundle sheath cells

Answer 1

The cost of NOT performing 2 cycles of photorespiration is

4 C in the form of 2 molecules of phosphoglycolate

As temperature increases, the quantum yield of photosynthesis in C3 plants is directly affected by

The decreasing ratio of CO2 to O2 in the aqueous phase

In CAM plants and ‘regular’ C4 plants, the enzyme that first fixes CO2 into an organic molecule is

Phosphoenolpyruvate carboxylase (PEPC) for both

In CAM (crassulacean acid metabolism) plants, when and where are sugars produced?

During the day, in mesophyll cells

In ‘regular’ C4 plants, when and where are sugars

produced?

During the day, in bundle sheath cells

In C3 cells the first organic molecule formed by fixing carbondioxide is a 3 carbon molecule, hence the name C3 plants.

In C4 cells in order to reduce photorespiration (reaction of RuBisCo with O2) the CO2 is fixed by Phosphoenol Pyruvate carboxylase (PEPC) eventually to form malate in mesophyl cells. The malate is then transported to bundle sheath cells (where photosynthesis takes place) and is converted back to CO₂ and other products. This CO2 is used by Rubisco in the bundle sheath cells to form glucose.  

CAM plants are a subset of C4 plants which store the CO2 as malate in vacuoles of mesophyll cells during night in order to reduce wastage of water ( as a result of opening stomata during day time). This malate is the broken down to release CO2 which enter photosynthesis during day time in the same cells.