Untitled Document
Contact Us    |   Register
SITE SEARCH
HOME
ONLINE COMMUNITY
MEMBERSHIP
MEETINGS & EVENTS
PUBLICATIONS/RESOURCES
CAREERS
GOVERNANCE
SECTIONS
AWARDS & FUNDING
EDUCATION & RESEARCH
PUBLIC AFFAIRS
EDUCATION FOUNDATION
ABOUT US


seo services

garcinia cambogia extract

cash loans

Chapter 13

Carbohydrate Metabolism

 

In this chapter, the complexity and the unique nature of plant carbohydrate metabolism have been presented. The differences between this form of metabolism in plants and that in other organisms stem from two factors.
      First, unlike other organisms, plants metabolize carbohydrates in two compartments, the cytosol and plastids, with most of the biosynthetic activity occurring in the latter compartment. All plant tissues have plastids, but the primary metabolic activity of these organelles varies extensively. The metabolic activity of a tissue as a whole is determined to a large extent by the enzyme complement of the plastids it contains. This characteristic of plant cells has a major impact on the regulation and characteristics of the carbohydrate metabolism pathways that generate building blocks for the biosynthetic activities localized in the plastids.
      Carbohydrate metabolism in the cytosol is connected with plastid metabolism by a series of carriers in the plastid envelope. Each plastid type has a different group of carriers, which usually reflects the nature of the biosynthetic activity within the organelle. Universally present, however, is the TPT, which exchanges triose phosphate for inorganic phosphate. The overall regulation of carbohydrate metabolism is linked to the activity of this and the other transporters. The TPT connects the cytosol with the plastid stroma at about the midpoint of the glycolytic pathway. For this reason, the regulation of glycolysis differs from that in other organisms, in which metabolism is regulated by the supply of nutrients.
      Second, all cells in a plant have to withstand changes in the external environment without the homeostatic mechanisms that stabilize the milieu surrounding animal cells. This has led to an inherent flexibility in plant metabolism reminiscent of that seen in some microorganisms. Often, several enzymes can catalyze a single step in a pathway. Certain of these enzymes appear to bypass principal reactions involved in carbohydrate metabolism, although mechanisms for the control of these bypasses have yet to be elucidated.
      Some of the most fundamental aspects of plant metabolism, such as the role of pyrophosphate and the control of its concentration, are still not understood. Considerable opportunities for future discovery await those who read this chapter and wish to pursue a better understanding of plant carbohydrate metabolism and its regulation.


© Copyright American Society of Plant Biologists 2013 (All Rights Reserved)