Thursday, April 14, 2011

Alternative mechanism of C fixation occurs in C4 and CAM plants

C4 plants:
1. occurs both in mesophyll + bundle sheath cells.
2. CO2 fixation is catalyzed by PEP carboxilase in mesophyll cells and sugar formation by RUBISCO in bundle sheath cells via Calvin cycle.
3. First product of CO2 fixation is a 4C compound oxaloacetate in C4 plants.

CAM plant:
1. live in hot climatic conditions
2. both C3 and C4 cycles occur.
4. fix CO2 during the night + synthesise sugar during the day.
5. G3P produced = used for the synthesis of sugars, amino acids and fatty acids.
6. Sugars formed = glucose, sucrose, starch + cellulose.
7. Lipids:
·  formed from glycerol + fatty acids.
·  Glycerol = formed directly from G3P
·  fatty acids = built from acetyl coenzyme A.
8. Protein formed by: conversion of G3P --> acetyl Co A (enters Krebs cycle) --> α-glutarate --> glutamate --> transamination --> form amino acids + proteins.

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