BIO 3465 - Laboratory 9 - Photosynthesis - Dark reactions

BIO 3465 - Laboratory 9 - Photosynthesis - Dark reactions -...

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BIO 3465 Plant Physiology Laboratory 9 PHOTOSYNTHESIS DARK REACTIONS Goal: Plant produces starch as a major storage compound. During photosynthesis the Calvin cycle produces G3P, a Triose phosphate. This Triose phosphate is converted to starch through a series of enzymatic reactions. Goal of this lab is to show the involvement of photosynthesis in starch synthesis. Second part of the lab will show photosynthesis actually necessary for the synthesis of sugars. These sugars will then be converted to starch even in the absence of photosynthesis. Additionally, you will learn about anatomical difference between C 3 and C 4 plants and its relevance to the mechanism. INTRODUCTION: The process of photosynthesis that produces carbohydrates by using CO 2 , H2O and light energy is known as photosynthesis . This process can be divided into two major phases. 1) light reactions that produce ATP (energy source) and NADPH (reducing power). These two products from light reactions are then be utilized in the second phase, 2) dark (light-independent) reactions. While both types of reactions are confined to chloroplasts, two processes are spatially separated inside the chloroplast as light reactions occur in thylakoid membranes and the dark reactions occur in stroma. In some cases, the two reactions may be separated temporally (see below). Dark reactions are also known as Calvin cycle as the second phase of photosynthesis is a cyclic process. Calvin cycle consists of 3 phases, 1) carbon fixation or carboxylation phase, 2) reduction phase, and 3) substrate regeneration phase (Figure 1). Figure 1: Major phases of Dark reaction (Calvin cycle). In this cyclic process CO 2 is fixed using the substrate Ribulose 1,5 bisphosphate (RuBP) and the products of light reactions, ATP and NADPH.
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This note was uploaded on 11/09/2011 for the course BIO 101 taught by Professor Pesthy during the Fall '07 term at Texas State.

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BIO 3465 - Laboratory 9 - Photosynthesis - Dark reactions -...

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