There are two types of plants, C3 and C4. C3 plants use the Calvin Cycle to gene

Question

There are two types of plants, C3 and C4. C3 plants use the Calvin Cycle to generate sugar. C4 plants use phosphoenol pyruvate to make malate and oxaloacetate which will eventually be used to make sugar. Both types of plants have stomatas (openings on leaves that can be opened and closed) for CO2 entry. In addition, water is also lost through the stomata. C3 plants are only able to synthesize sugar at relatively high CO2 levels because photosynthesis will stop when CO2 production from the mitochondria equals the use of CO2 in the chloroplasts. C4 plants are able to continue photosynthesis even at low CO2 levels.  

(1) Why are C4 plants able to survive in hot, dry conditions when C3 plants are not?

(2) Plants can develop cancer but it is usually from an infection not from the ionizing rays of the sun. What part of the photosynthesis pathway do you think protects the plant form sun damage? ( 4 pts)

Explanation / Answer

1)The C4 plants able to survive in hot, dry conditions because they use two stage process.Co2 is fixed in mesophyll cell to form malic acid . The reaction involves phosphoenol pyruvate which fixes CO2 and catalyses by PEP-carboxylate. It forms oxaloacetic acid which is converted to malic acid. the malic acid goes through cell membrane and spilts in to co2 and a 3 carbon compound.the CO2 then enters the Calvin cycle in a chloroplast of the bundle sheath cell and produces G3P and sucrose, starch and other carbohydrates,and enter cells in to energy transport system.

In c3 plants the process occur in one step called C3 plants have the disadvantage that in hot dry conditions their photosynthetic efficiency suffers because of a process called photorespiration.

2)carotenoids protect the plant photosynthetic pathway from sun damage.......

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