NEET AIPMT SOLVED PAPER SCREENING 2005

  • question_answer
                    Photosynthesis in \[{{C}_{4}}\] plants is relatively less limited by atmospheric \[C{{O}_{2}}\] levels because:               

    A)                 four carbon acids are the primary initial \[C{{O}_{2}}\] fixation products

    B)                 the primary fixation of \[C{{O}_{2}}\] is mediated via PEP carboxylase

    C)                 effective pumping of \[C{{O}_{2}}\] into bundle sheath cells

    D)                 RUBISCO in \[{{C}_{4}}\] plants has higher affinity for \[C{{O}_{2}}\]

    Correct Answer: B

    Solution :

                    The fixation of \[C{{O}_{2}}\] in \[{{C}_{4}}\] plants takes place in two places and by two different organic compounds. Phosphoenol pyruvate (PEP) is found in mesophyll cells which primarily fixes atmospheric \[C{{O}_{2}}\] into oxaloacetic acid (4C).                 RUBISCO is present in bundle sheath cells where final fixation of \[C{{O}_{2}}\] in hexose sugars takes place. \[C{{O}_{2}}\] is primarily fixed by PEP carboxylase because this enzyme has greater affinity to \[C{{O}_{2}}\] than RUBISCO.


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