CAM & C4 Plants

Question 1

What is Photorespiration?

Answer 1

Photorespiration is when Rubisco in the Calvin Cycle adds an O2 to the RuBP instead of a CO2, which produces a 2-carbon compound. This occurs because O2 is more soluble than CO2 at higher temperatures.

Photorespiration consumes the O2 (and organic fuel), and releases CO2 without producing ADP or Glucose

Question 2

Why does Photorespiration occur?

Answer 2

Photorespiration occurs when the Stomata of a C3 (normal) plant closes. This could be due to the plant being in an Arid or low CO2 environment.

Question 3

What are C4 plants?

Answer 3

C4 plants are plants that minimize the cost of photorespiration by incorporating CO2 into
four-carbon compounds in
mesophyll cells.

This process requires PEP Carboxylase.

Question 4

How does the C4 pathway work?

Answer 4

CO2 enters the mesophyll cell and gets converted into Oxalacetate by PEP Carboxylase. This oxalacetate then gets converted into malate which releases CO2 upon reaching the bundle-sheath cell.

The CO2 then goes through the normal Calvin Cycle.

Question 5

What’s an example of a C4 plant?

Answer 5

Sugarcane.

Question 6

What are CAM plants?

Answer 6

CAM plants are plants that open their stomata at night to incorporate CO2 into Malic acid. They keep their stomata closed during the daytime.

Question 7

How does the CAM plant pathway work?

Answer 7

The Stomata is opened at night which allows CO2 to enter the plant and be incorporated into Malic Acid (forming Malate).

During daytime when the stomata is closed, the Malic Acid releases the Malate and consequentially, it releases the CO2 which allows the plant to go through the Calvin Cycle and produce Glucose.

Question 8

What’s an example of a CAM plant?

Answer 8

Pineapple and Aloe Vera.

Question 9

What is the C4 pathway and CAM pathway referred to as?

Answer 9

C4 = Spatial Separation (Bundle sheath cell)

CAM = Temporal separation (CO2 incorporated into Malic Acid. Stomata opened at night, closed during day).