Question

1. In plants, what cells strip a carbon, as CO2, from the four carbon compound and return the three-carbon remainder to the mesophyll cells?

2. Fill in the blanks: In C4 plants, carbon fixation and the calvin cycle are __________ separated but in CAM plants, carbon fixation and the calvin cycle are ________ separated.

Thank you!!

Answer 1

Please find answer of first question:

1. Answer- Bundle of sheath

• Bundle sheath cells arranged into tightly packed sheaths around the veins of the leaf. Mesophyll cells loosely arranged cells located between the bundle sheath and leaf surface.
• Calvin cycle confined to the chloroplasts of the bundle sheath cells. Cycle preceded by the incorporation of CO2 into the organic molecules in the mesophyll. An enzyme, PEP, adds CO2 to form oxaloacetate. PEP can fix CO2 efficiently when rubisco cannot.
• Mesophyll cells pump these 4 carbon compounds into bundle sheath cells.
• Bundle sheath cells strip a carbon from the four carbon compound as CO2, and return the three carbon remainder to the mesophyll cells.
• The bundle sheath cells then use rubisco to start the Calvin cycle with an abundant supply of CO2.
• Mesophyll cells pump CO2 into the bundle-sheath cells, keeping CO2 levels high enough for rubisco to accept CO2 and not O2.
• C4 photosynthesis minimizes photorespiration and enhances sugar production.
• C4 plants thrive in hot regions with intense sunlight

2. Answer;

• The initial steps of carbon fixation are separated structurally from the calvin cycle in C4 plants where as in CAM plants, the two steps occur at separate times but within the same cell.
• C3 plants fix carbon dioxide into a 3 carbon molecule. They do not separate carbon fixation from the Calvin cycle. C4 plants fix carbon dioxide into a 4 carbon molecule. They separate carbon fixation from the Calvin cycle.
• C4 plants separate CO2 fixation and the Calvin cycle into different cells. CAM photosynthesis separates CO2 fixation and the Calvin cycle by time.
• CO2 fixation and the Calvin cycle are separated by space- C4 plant. (C4 in space)
• CO2 fixation and the Calvin cycle are separated by time- CAM Plant